Black Holes through Cosmic Time
In the last decade we have seen profound advances in our understanding of the composition and evolution of the Universe. Prominent among these is the discovery that essentially all galaxies with stellar bulges contain supermassive black holes (SMBH), which are believed to be the relics of accretion in active galactic nuclei (AGN). Further, the masses of SMBHs are tightly correlated to the properties of their host bulges, and the energy released by AGN may have a significant effect on the star formation history of galaxies. Thus it is increasingly clear that growth and evolution of black holes and galaxies are linked through cosmic time.
X-ray surveys are exceptionally powerful tools for studying the evolution of black holes and their host galaxies, by detecting large numbers of AGN over a wide range of redshifts and cosmic environments from voids to groups and clusters. With its superb angular resolution, low background, and sensitivity in the energy range 0.5 8 keV, Chandra has been at the forefront of recent extragalactic surveys. In this article we provide an overview of some of the leading Chandra surveys, and describe some recent results on the composition of the cosmic X-ray background (CXB), the evolution of black hole accretion, the nature of AGN populations, and links between AGN and their host galaxies and environments. This is an extremely active and exciting field, with many key contributions made by XMM-Newton, Suzaku, INTEGRAL, Swift, and other space and ground-based observatories; here we will focus on just a few representative results from Chandra surveys.
Breadth and depth in Chandra surveys
Chandra extragalactic surveys range from very deep and narrow to shallow and very wide, allowing us to study the broadest possible range in redshift and luminosity (Figure 1). The deepest existing X-ray surveys are the Chandra Deep Fields (CDFs) North (Alexander et al. 2003) and South (Luo et al. 2008), each with 2 Ms total exposure. Owing to Chandra's unparalleled spatial resolution, these observations are not limited by confusion and probe to depths more than 6 times fainter than is accessible with any other X-ray observatory. The CDFs have yielded extraordinary progress in understanding faint X-ray populations and resolving the CXB. However, the X-ray luminosity density is dominated by more luminous X-ray sources that are rare in the CDFs, so Chandra also has undertaken several shallower surveys over wider areas to study these objects. These surveys include, in order of increasing area, ELAIS-N (Manners et al. 2003), the Extended CDF-S (Lehmer et al. 2005), AEGIS-X (Laird et al. 2009), CLASXS and CLANS (Trouille et al. 2008; CLANS is comprised of data from the SWIRE/Chandra survey; Wilkes et al. 2009), C-COSMOS (Elvis et al. 2009), XDEEP2 (Murray et al. 2008) and XBoötes (Murray et al. 2005). The areas and corresponding flux limits for these surveys are shown in Figure 2. Most surveys also have extensive multiwavelength coverage with HST, Spitzer, ground-based optical imaging and spectroscopy, radio, and other observations (Figure 3), allowing us to understand the detailed spectral energy distributions (SEDs) and environments of the X-ray sources. For a more detailed review of X-ray surveys with a focus on the deepest fields, see Brandt & Hasinger (2005).
In addition to dedicated Chandra observations in contiguous survey fields, the Chandra Multiwavelength Project (ChaMP) uses archival data for optical imaging and spectroscopic followup of serendipitous sources from 392 (non-contiguous) ACIS pointings (Green et al. 2004, Kim et al. 2007). The large samples allow removal of potentially biasing PI-targeted objects and provide large statistical subsamples immune to cosmic variance. Similar follow-up of serendipitous hard X-ray (2 10 keV) sources has been undertaken by the Serendipitous Extragalactic X-ray Source Identification (SEXSI) program (Harrison et al. 2003).
Resolving the cosmic X-ray background
Since its discovery in rocket flights at the dawn of X-ray astronomy (Giacconi et al. 1962), the origin of the diffuse extragalactic X-ray background has been one of the leading questions in high-energy astrophysics. With the exceptional sensitivity of the CDFs, it is now clear that almost all of the extragalactic CXB at energies <2 keV arises from X-ray point sources. The primary contributors are AGN, which dominate the radiative energy density of the Universe at X-ray wavelengths.
The precise fraction of the CXB that is resolved in X-rays has been the subject of numerous studies. Moretti et al. (2003) summed the X-ray emission from sources detected in a variety of Chandra and other surveys, and compared the total to an estimate of the total CXB, concluding that ~90% of the CXB at E < 2 keV was resolved. Worsley et al. (2005) performed a similar analysis as a function of energy, and showed that the resolved fraction drops at energies >5 keV, indicating a "missing" population of hard sources, which may include AGN that are highly obscured by intervening gas (see below). Hickox & Markevitch (2006) took a complementary approach, measuring the absolute flux of the unresolved CXB in the CDFs, and showed that the resolved fraction of the 1-2 keV CXB is ~80%.
Hickox & Markevitch (2007b) demonstrated that only 7% ± 3% of the 1-2 keV CXB remained unresolved after excluding HST sources in the GOODS field, in broad agreement with a stacking analysis by Worsley et al. (2006). By studying the distribution of X-ray counts at the HST source positions, Hickox & Markevitch (2007a) showed that the logN-logS for faint, unresolved X-ray galaxies in the CDFs is consistent with an extension of the observed population of faint star-forming galaxies, rather than AGN. These results indicate a large population of faint X-ray sources that may be accessible with deeper observations in the CDFs.
The cosmic evolution of black hole growth
A key question in black hole evolution is: where and when did black holes gain their mass? Unlike galaxies (for which we can determine ages for the stars), black holes have no "memory" of their formation history. Therefore, to determine the cosmic evolution of black hole growth we must observe that growth directly, by measuring how the space density of accreting black holes evolves with cosmic time. A number of authors have used the wealth of spectroscopic redshifts available in X-ray surveys to derive the X-ray luminosity function for AGN at a range of redshifts from the local Universe to z > 4 (e.g., Ueda et al. 2003; Barger et al. 2005; Hasinger et al. 2005; Silverman et al. 2008a). To cover the largest possible region in the luminosity-redshift plane, these studies combine data from narrow, deep and wide, shallow Chandra surveys, as well as data from XMM-Newton, ASCA, Rosat, and other missions.
These studies have shown that AGN activity has a relatively complex and interesting evolution with redshift. Chandra results favor a model of luminosity-dependent density evolution (LDDE), in which the number density of AGN evolves differently for sources of varying luminosities. These results provide evidence for downsizing, in which the density of the most luminous AGN peaks earlier in cosmic time than for less luminous objects (e.g., Steffen et al. 2003; Hasinger et al. 2005, see Figure 4), which can be shown to imply that large black holes are formed earlier than their low-mass counterparts (e.g., Merloni & Heinz 2008; Shankar et al. 2009). Qualitatively similar downsizing has been observed for star formation in galaxies (e.g., Cowie et al. 1996), providing a circumstantial link between SMBH and galaxy evolution.
Understanding X-ray source populations
The large numbers of AGN detected in extragalactic surveys allows for robust statistical studies of AGN populations. Particular effort has been focused on measurements of X-ray spectra, which provide insights into the nature of AGN accretion. Tozzi et al. (2006) performed spectral fits for hundreds of sources in the CDF-S, while Green et al. (2009) measured the spectra for >1000 SDSS quasars in ChaMP, including 56 with z > 3. These studies show that in general, the unabsorbed spectra of AGN have remarkably uniform power-law continua. However, Chandra studies also have shown that X-ray spectra and X-ray to UV SEDs of AGN get harder with decreasing Eddington ratios1 (e.g., Steffen et al. 2006; Kelly et al. 2008), similarly to black hole X-ray binaries (Remillard & McClintock 2006). X-ray surveys also can constrain the numbers of AGN that are absorbed by intervening gas, which preferentially absorbs low-energy X-rays and so hardens the observed spectrum. The total spectrum of the CXB is harder than the emission from a typical unabsorbed AGN, indicating a significant contribution from absorbed sources. In the local Universe, 75% or more of optically selected Seyfert galaxies are obscured by dust (Maiolino & Rieke 1995), and Chandra surveys suggest a similar fraction are absorbed in X-rays. Further, there is evidence that the obscured fraction rises at lower luminosities and may increase at higher redshifts (e.g., Ueda et al. 2003; Steffen et al. 2003; Hasinger 2008), which may constrain models in which AGN provide radiation pressure feedback on surrounding gas. In addition, X-ray studies have confirmed the identification of obscured AGN detected in optical and IR observations (e.g., Hickox et al. 2007; Polletta et al. 2008; Donley et al. 2008; Alexander et al. 2008b).
Using the observed luminosity functions, spectral shapes, and absorbing columns derived from Chandra and other surveys, it has been possible to model the spectrum of the total cosmic X-ray background (e.g., Treister & Urry 2005; Gilli et al. 2007). While these models still have significant uncertainties (particularly in the number of highly obscured AGN), their success implies that we may be converging on a coherent picture for the cosmic evolution of black hole growth. One caveat however, is that the low numbers of X-ray counts in surveys make it difficult to distinguish absorption from intrinsically hard spectra for faint sources. If the X-ray spectra of AGN become harder at low Eddington ratio, this could produce a large number of low-luminosity, X-ray hard AGN that would be classified as "absorbed" in current analyses (Hopkins et al. 2009). Future deep surveys or detailed stacking of X-ray spectra may be able to break the degeneracy between intrinsic spectral shape and absorbing column.
Links between AGN and galaxy evolution
Finally, Chandra surveys have allowed for detailed examination of the host galaxies and environments of X-ray AGN, providing insight on the role of AGN in the evolution of galaxies. One powerful diagnostic is the color-luminosity distribution for the galaxies that host AGN. Galaxies are known to be divided into two types in color-magnitude space: the red sequence of luminous, passively evolving galaxies, and the blue cloud of less luminous, star-forming systems. Interestingly, a number of Chandra studies have found that at z ~< 1, luminous X-ray AGN (unlike radio, optical, or infrared-selected AGN) are preferentially found in the "green valley", with colors intermediate between blue and red galaxies (e.g., Nandra et al. 2007; Georgakakis et al. 2008; Silverman et al. 2008c; Hickox et al. 2009, see Figure 5), indicating that X-ray AGN may be associated with the transition of galaxies from the blue cloud to the red sequence, and may be responsible for quenching the star formation in galaxies through feedback (Bundy et al. 2008; Georgakakis et al. 2008). Further, studies of the environments and clustering of AGN find that Chandra X-ray AGN are preferentially found in overdense regions characteristic of galaxy groups (e.g., Yang et al. 2006; Georgakakis et al. 2007; Silverman et al. 2008b; Hickox et al. 2009; Coil et al. 2009). Models suggest it is these environments where star formation shuts off in massive galaxies; AGN may play a role in the initial quenching of star formation, or in subsequent heating that prevents gas from cooling and further forming stars (e.g., Croton et al. 2006; Bower et al. 2006; Hopkins et al. 2008).
Chandra surveys also have explored the presence of AGN associated with massive, vigorously star-forming galaxies in the distant Universe (z ~ 2). X-ray studies of starburst galaxies selected in the CDFs with observations in the submillimeter (e.g., Alexander et al. 2005) and infrared (Daddi et al. 2007; Fiore et al. 2008) have provided evidence for a large density of highly obscured AGN in galaxies co-eval with the formation of the bulk of their stellar mass. Alexander et al. (2008a) found that the AGN in submm galaxies have black hole masses that are roughly consistent with those expected from the local relation between black hole mass and bulge mass, indicating that there may be continuous feedback between star formation and accretion in these systems. While the precise nature of the AGN population associated with luminous starbursts is not yet clear, these studies point further towards important links between the growth of galaxies and their central SMBHs.
Future X-ray surveys will provide more sensitive observations and larger AGN samples to study the characteristics and evolution of SMBH accretion in greater detail. One future prospect with Chandra is even deeper observations in the CDFs. Chandra's high angular resolution will allow it to observe significantly deeper (up to 8 Ms or more) without reaching the confusion limit in the central regions (Alexander et al. 2003). This would allow the detection of a new population of extremely faint star-forming galaxies, as well as providing better photon statistics for the sources that have already been resolved. The upcoming NuSTAR2 mission (to launch 2011) will provide an unprecedented all-sky survey at hard X-ray (6-80 keV) energies, while the eROSITA3 instrument on the Spectrum X-Gamma observatory (scheduled for launch in 2011-2012) will survey the sky at 0.2-12 keV energies and will provide enormous samples of X-ray AGN. Among missions proposed for the future, Simbol-X4 (target launch 2014) would provide high angular resolution (better than 30'') and high sensitivity in the ~0.5-80 keV range, while EXIST5 would conduct a large-area X-ray survey at the very hard (5-600 keV) energies. The Wide-Field X-ray Telescope6 would provide an analog to SDSS in the X-ray band, detecting >107 X-ray AGN over >10,000 deg2 in the energy range 0.1-4 keV (possibly extending to 6 keV). Further, the enormous sensitivity of the International X-ray Observatory7 would allow us to study in detail the spectra of large numbers of faint AGN. These future missions will be essential to build on our understanding of the growth of black holes and their place in the larger picture of galaxy and structure formation in the Universe.
Re-Analysis of the XRCF Data
A recent re-analysis of the XRCF data showed that the molecular contamination was already present on the mirrors during testing at the XRCF. The initial empirical XRCF correction essentially corrected for the gross effects of the molecular contamination, but had insufficient detail to resolve the Ir-M edge discrepancy. The addition of the explicit 22Å thick contamination layer provided the required detail to fix the Ir edge problems, but essentially doubled the contamination layer, over-correcting the gross features.
During XRCF testing, a system of shutters was placed behind the HRMA so that the response of the 4 shells could be measured independently. Two instruments were used at the focal plane; a flow proportional counter (FPC) and a solid state detector (SSD). A re-analysis of single-shell SSD measurements of a continuum source, this time including molecular contamination, led to estimates of the contamination layer depths on the individual shells (18-28A) which are in good agreement with the result derived from the on-orbit blazar gratings spectra. After incorporating this effect into the model, an additional gray correction was required to bring the model's prediction for the XRCF measured effective area in line with that measured. This correction is similar in purpose to the XRCF correction factor used in earlier models, but is derived from a different weighting of the FPC and SSD measurements. There are statistically significant differences between those measurements; the current method of weighting is, we believe, an improvement over the previous method. The resolution of the discrepancies between the two detectors is the subject of an ongoing investigation, which may lead to improvements in our understanding and subsequent improvements to the HRMA effective area.
The new version of the HRMA effective area (CALDB 4.1.1) is based on the predictions of the new model, including the as-measured contamination depths and the gray correction. Since the depth of the molecular contaminant varies from shell-to-shell, an updated version of the HETG efficiency was also released in CALDB 4.1.1 to maintain cross-calibration consistency between the HEG (which intercepts photons from the two smallest mirror shells) and MEG (which intercepts photons from the two largest mirror shells).
Comparison of Cluster Temperatures with Updated HRMA Effective Area
Figures 20 and 21 show a comparison of ACIS and MOS derived cluster temperatures with the old and new versions of the HRMA effective area. Temperatures were determined in both a hard (2.0-7.0 keV) and broad (0.5-7.0 keV) energy band. These figures show that there is now good agreement between ACIS and MOS derived temperatures in the hard energy band for all cluster temperatures. In the broader energy band, ACIS derived temperatures are slightly higher than MOS temperatures. This results from lower MOS temperatures derived in the broad energy band compared to the hard energy band. Our studies have also show that the MOS and PN produce consistent temperatures in both energy bands.
While the new HRMA effective area is a significant improvement over the previous version, the Chandra optics team is still investigating a few unresolved issues with the XRCF data which may lead to further improvements in the HRMA effective area.
Chandra Calibration Review
The Chandra Calibration Review (CCR) is held regularly for the dissemination and advancement of our understanding of the performance and capabilities of the Chandra X-ray Observatory. It is intended to share the Chandra teams' knowledge of the detectors, gratings, mirrors, and aspect system with the community while encouraging participation and feedback in the process of calibrating the observatory. Abstracts are solicited on calibration related issues.
This year, we will again be holding the Calibration Review in conjunction with an anniversary symposium, the Ten Years of Science with Chandra Symposium in Boston, Massachusetts. Calibration talks will be presented on Monday September 21, prior to the Symposium. Calibration-related posters will be displayed throughout the Symposium, which runs from Tuesday, September 22 through Friday, September 25.
For more information, see http://cxc.harvard.edu/ccr/
Bringing Cosmology to the Public
Timing for the publicity of science results can be challenging. There are many factors to juggle: acceptance of the paper into a journal, schedules of the main scientists, constraints from NASA, and others. We try to avoid holding press conferences near the holidays, since we don't want to hear that half of the world's science reporters are heading off for vacation instead of writing about our latest result. But, mid-December can work just fine, since for the second year in a row we have held a successful press conference at this time. Last year, the work on 3C321 by Dan Evans and others (which became known as the 'death star galaxy') was a big hit in the media. http://chandra.harvard.edu/photo/2007/3c321/. This year, a press conference was held on December 16th, 2008 to announce "Dark Energy Found Stifling Growth in Universe", work led by Alexey Vikhlinin at CfA. http://chandra.harvard.edu/chronicle/0408/darkenergy/. This press conference generated widespread press coverage, including the New York Times, the Washington Post, USA Today, NPR, the Associated Press, Reuters and the Economist, and many others.
Why did this result generate so much attention? There are several reasons. First, it represents a significant advance in astrophysics, and that is important to experienced science journalists. Also, several well-regarded astronomers who were not involved with the research gave positive supporting comments, and this helped reporters appreciate the significance of the findings. Alexey's work gives the best results so far from studying the effects of cosmic acceleration on the growth of large-scale structure, which is fundamentally different from studying cosmic acceleration itself. Not only does it allow important properties of dark energy to be independently determined, but it permits constraints on the behavior of gravity over large scales, when compared with distance measurements. In other words, this work was unlike anything else that reporters had heard before: a key to getting and keeping their attention.
It is worth noting that Alexey and his colleagues did not publish their cosmological constraints until their survey was complete and they had carried out detailed simulations and cross-checks of their results. This patience was rewarded with the recognition by cosmology experts that their results represented more than an incremental advance. This may not have been the case if the results had been allowed to trickle out. With this approach, there was a danger that the basic results would be "scooped" by a different team, for example a group using weak lensing as a probe of growth of structure, but a competitive result did not emerge.
Another important reason for the success of this story is that dark energy is now one of the hottest research fields in science, with new papers appearing almost every day on astro-ph. According to the Dark Energy Task Force, "nothing short of a revolution in our understanding of fundamental physics will be required to achieve a full understanding of the cosmic acceleration." As a result of this importance, an aggressive and expensive set of observational programs are either underway or planned to study dark energy in more detail. This has reached the level where there has even been a backlash with, for example, written and verbal debates between a prominent astronomer and physicist about whether such attention is good for the field of astronomy. These developments are familiar to many astronomers, of course, but they have also been noticed by science reporters.
Finally, and perhaps most importantly, cosmology is one of the most exciting and stimulating fields in all of science for the public. Questions like "What is the Universe made of?," "What did the Universe look like in the past?," and "What is the destiny of the Universe?" have been asked for millennia. If a result can give interesting new answers to any of these big questions, it is compelling to the public and to reporters. If it can address all of these questions, as the recent work does, that is even better. Also, studies of dark energy address intriguing questions about the nature of the vacuum, such as whether it is possible for nothing to weigh something.
Given the strength of this story, it did not matter that the Chandra images were not the most eye-catching ones we have ever released, or that the indirect effects of repulsive gravity were not trivial to explain, or that this result did not contain any major surprises. The advantages overwhelmed the disadvantages, resulting in the excellent press coverage.
Other Chandra results on cosmology have also received a significant amount of press coverage, including the work on the Bullet Cluster by Doug Clowe and collaborators in 2006, and independent work on dark energy by Steve Allen and collaborators in 2004. We continue to look for new results in this field to publicize. Maybe we'll do another mid- December press conference!
CXC 2008 Science Press Releases
|January 9||Ralph Kraft (CfA)||Cen A||Jet Power and Black Hole Assortment Revealed in new Chandra Image|
|January 10||Rodrigo Nemmen (Penn State)||9 galaxies||Chandra Data Reveal Rapidly Whirling Black Holes|
|February 13||Rasmus Voss (MPE)|
Gijs Nelemans (Radboud Univ.)
|SN 2007on||Possible Progenitor of Special Supernova Type Detected|
|March 20||Armin Rest (Harvard)||SNR 0509-67.5||Action Replay of Powerful Stellar Explosion|
|April 28||John Fregeau (Northwestern)||13 globular clusters||Oldest Know Objects May be Surprisingly Immature|
|May 14||Steven Reynolds (North Carolina State)||G1.9+0.3||Discovery of Most Recent Supernova in Our Galaxy|
|June 18||Sera Markoff (Univ. Amsterdam)||M81||Black Holes Have Simple Feeding Habits|
|July 16||Philip Humphrey (Univ. California Irvine)||NGC 4649||A New Way ot Weigh Giant Black Holes|
|September 25||Franz Bauer (Columbia)||SN 1996cr||Powerful Nearby Supernova Caught by Web|
|October 30||Gary Steigman (Ohio State)||Bullet Cluster||Searching for Primordial Antimatter|
|December 16||Alexey Vikhlinin (CfA)||86 galaxy clusters||Dark Energy Found Stifling Growth in the Universe|
Useful Chandra Web Addresses
To Change Your Mailing Address: http://cxc.harvard.edu/cdo/udb/userdat.html CXC: http://chandra.harvard.edu/ CXC Science Support: http://cxc.harvard.edu/ CXC Education and Outreach: http://chandra.harvard.edu/pub.html ACIS: Penn State http://www.astro.psu.edu/xray/axaf/ High Resolution Camera: http://hea-www.harvard.edu/HRC/HomePage.html HETG: MIT http://space.mit.edu/HETG/ LETG: MPE http://www.mpe.mpg.de/xray/wave/axaf/index.php LETG: SRON http://www.sron.nl/divisions/hea/chandra/ CIAO: http://cxc.harvard.edu/ciao/ Chandra Calibration: http://cxc.harvard.edu/cal/ MARX simulator http://space.mit.edu/ASC/MARX/ MSFC: Project Science: http://wwwastro.msfc.nasa.gov/xray/axafps.html
Chandra Science Publications
Paul Green, for CDO
Chandra is nearing a decade of robustly successful science observations. The number of Chandra-related science publications continues to grow strongly. The figure here shows the number of refereed Chandra Science Papers by publication year.
The Chandra Data Archive (CDA) Group at the CXC tracks such publications by a daily query to the ADS. All publications are scanned and reviewed by hand, categorized by several parameters and entered into the Bibliography Database. The website http://cxc.harvard.edu/cda/bibstats/ is updated monthly with fresh plots and data tables. A full list of the articles tallied is produced, with links to the ADS abstracts. The pages also contain detailed descriptions of the classifications we use, for instance, what do we define as a "Refereed Chandra Science Paper". The CXC also compiles statistics on Chandra-related PhD dissertations.
There is some unavoidable lag time for papers to appear in the ADS after they are published, and then the CXC Bibliography Database is updated within a couple of weeks of these new ADS entries. From experience, the asymptotic paper count for a given year is thus not available until about April of the year following, which explains why we mark the last bar differently in Figure 22.
Keep those papers coming!
CIAO 4.1: with a whole new Sherpa!
Version 4.1 of the Chandra Interactive Analysis of Observation (CIAO) software was released in December 2008, followed immediately by a small patch 4.1.1 to include data files for proposal planning purposes.
CIAO 4.1 includes several improvements and bug fixes to some of the CIAO tools, libraries and GUIs (the release notes describe all these in detail and Figure 23 shows an example), but the main feature of this release is an all-new non-beta version of Sherpa, the CIAO modeling and fitting package. A re-designed, re-written Sherpa was released for the first time as beta version in December 2007. Now, the fully functional package is available for the community
Sherpa supports forward fitting of 1-D X-ray spectra from Chandra and other X-ray missions, fitting of 1-D non-X-ray data, including ASCII data arrays, radial profiles, and lightcurves. The options for grating data analysis include fitting the spectrum with multiple response files required for example for overlapping orders in Chandra HRC/LETG observations. Modeling of 2-D spatial data is fully supported, including PSF and exposure maps effects.
The main new feature of the Sherpa redesign concerns the Sherpa's environment: it can be run in a S-Lang shell (http://www.s-lang.org/) or in Python (http://www.python.org/) with only very minor syntax differences. Users can select the language they prefer and in general will choose the language they have the most experience with, that their friends or colleagues use, or for which they can get the best support. In both cases they will gain scripting and programming capabilities, easier access to mathematical calculations, and access to other libraries written by the community. This new infrastructure greatly enhances the default Sherpa functions, and provides users with an environment for developing complex and sophisticated analysis.
Sherpa is designed to be used as a user-interactive application or in a batch mode. It is an importable module for the S-Lang and Python scripting and is available as a C/C++ library for software developers.
Sherpa internal data structures are exposed and fully accessible through high level user interface functions. This FIGURE 23: An example of thew new PRISM application and its interactive plotting/histogramming capabilities. The data file loaded into PRISM contains the results from 50,000 iterations of a Metropolis-Hastings sampler (see http://hea-www.harvard.edu/AstroStat/statjargon.html) used to evaluate the distribution of fit parameters for the best-fit model found by Sherpa. In this case the data is an image of a galaxy cluster with a bright point source close to the center. The data was fit with a gaussian2d component to represent the point source, a beta2d component for the cluster emission, and a flat background, all convolved with a PSF. Histograms of the cluster and point source center values have been overlaid using the "Interactive Histogram" option in PRISM; one window compares the X-axis values and one the Y-axis values. The window also allows the histogram properties (in this case the fill style and color) to be changed before plotting. As can be seen, although the x values are similar, the y values do not overlap which shows that the point source is offset from the cluster center. A third plot window shows a sample scatter plot of two fit parameters and was obtained with the "Interactive Plot" option in PRISM. accessibility allows users to develop their own complex analysis routines. For example users can input their own models, can write specific analysis procedures not included in the current Sherpa package or run many simulations required for the planning of future observations.
One example of such a user package is "Deproject", a Python module for X-ray clusters and other diffuse X-ray data that require 3D to 2D model deprojection. This Python extension module was developed by Tom Aldcroft and it is now available on the CXC contributed software web page: http://cxc.harvard.edu/contrib/deproject/
Possibly the main strength of Sherpa is its reliability in convergence. There are three optimization methods: "levmar", a modification of the Levenberg-Marquardt algorithm which uses the LMDIF algorithm (More 1978); "neldermead", A Nelder-Mead Simplex direct search (Nelder & Mead 1965); and "moncar", a Monte Carlo method based on the paper by Storn and Price (1997). These more robust algorithms are a complete replacement of the Sherpa OPTIM routines in CIAO 3.4.
Several statistics are available in Sherpa including χ^2 with various "weight" options, C statistics and the maximum likelihood statistics as defined by Cash. Users need to note that some options of χ^2 statistics shows bias in fitting low count data, so they have a choice of appropriate statistics for low count Poisson X-ray data.
More information on CIAO can be found at http://cxc.harvard.edu/ciao/. Sherpa documentation and sample analysis thread are at http://cxc.harvard.edu/sherpa/
J.J. More, "The Levenberg Marquardt algorithm: implementation and theory," in Lecture Notes in Mathematics 630: Numerical Analysis, G.A. Watson (Ed.), Springer-Verlag: Berlin, 1978, pp.105-116). J.A. Nelder and R. Mead (Computer Journal, 1965, vol 7, pp 308-313) Storn, R. and Price, K. "Differential Evolution: A Simple and Efficient Adaptive Scheme for Global Optimization over Continuous Spaces." J. Global Optimization 11, 341-359, 1997.
New Functionality for Proposers: PRoVis and MaxExpo
The CXC announces the availability of PRoVis. PRoVis, at http://cxc.harvard.edu/soft/provis provides interactive plotting of Chandra spacecraft roll, pitch, and target visibility for a selected celestial target, using a recent projected Chandra ephemeris. PRoVis replaces the old WebVis tool, and adds interactive functionality, live cursor readout, revised and expanded output data format, and a plethora of plotting format choices. For instance, by default, hatched regions highlight the thermal restrictions imposed by the Chandra pitch ranges available for your celestial target.
Spacecraft thermal constraints translate into restrictions on the maximum uninterrupted exposure time for a target, depending on the available pitch angle and season. CXC now also provides the MaxExpo page http://cxc.harvard.edu/proposer/maxexpo.html with up-to-date static plots and tables showing the maximum Chandra dwell time as a function of pitch angle and season. The information here is most useful for proposers whose observations require constraints for scientific reasons, to determine the maximum uninterrupted exposure time for a given target, once its pitch angle is known, e.g., using PRoVis!
The 6th Chandra/CIAO Workshop
After a pause of a few years (the 5th workshop occurred in 2003) and by popular demand, the Chandra X-Ray Center (CXC) resumed the Chandra/CIAO workshops with a 6th one during 3 days on October of 2008. The Chandra/CIAO workshops aim at helping users to work with the Chandra Interactive Analysis of Observations (CIAO) software.
The workshop included oral presentations by CXC "experts" and several hours of hands-on session where students could try to use CIAO "for real" with constant support from CIAO team members. Every presentation for this - and all previous - workshops can be found from http://cxc.harvard.edu/ciao/workshop/index.html In many cases these presentations are a very good starting point for new and old Chandra/CIAO users looking for a summary of a specific subject (e.g. Pileup Modelling, Source Detection, etc.).
About 30 people from all of the world and with a variety of backgrounds and expertise in X-ray data analysis attended the talks and the hands-on session, putting the CIAO tools and documentation to a real test!
A feedback survey distributed at the end showed us what we did well and where we could improve in the future. Many students expressed strong interest in an "Advanced CIAO Workshop" which we may try in the future. Everyone seemed to like the hands-on session and the availability of immediate on-site support. One survey answer for them all: "4. Did you get enough support during the hands-on session? That was simply perfect, and people were so nice!"
Thanks to all for coming and look out for the next announcement.
News from the Chandra Data Archives
Chandra Deep Fields
In 2008 we released new custom processed datasets for Chandra Deep Fields, North and South. These data sets contain the merged 2Ms observations for CDFN and CDFS. The credit for the reprocessing of these data goes to all of CXC Data Systems. Descriptions of and access to the datasets can be found from our Contributed Dataset Pages
Our Chandra Bibliography Database and classification system is undergoing a major overhaul and expansion. The database has been redesigned to be mission independent and to work with a new suite of tools for querying ADS, populating the database, downloading papers, and scanning papers for content in an automated fashion. Because of our improvements in scanning the content of papers, we now look at every astronomy paper in ADS, thus making our database much more complete. However, because of the high volume, we still limit physics and instrument papers to those which contain Chandra and its instruments in the title or abstract.
The new system also has a plug-in feature which gives a data center the opportunity to connect mission-specific information to paper content. We use this feature to flag instrument configuration information in the bibliography database from the Chandra Observation Catalog. The system also keeps a complete history of edits made to bibcodes and allows for multiple reviewers of papers which we use for quality assurance.
The expansion includes flagging observatories, catalogs, and surveys found in Chandra-related publications. We currently flag sixty-six observatories and sixty-nine catalogs and surveys and will be adding to these lists during our migration. A flag to an observatory, catalog, or survey also includes a flag to a wavelength, making multi-wavelength queries of papers more meaningful.
We have started migrating to the new system and plan to have it complete and accessible by the end of the year. During the migration process we will be studying the content of articles for more content-related flags and hope to work with ADS to make our content-related flags available to them. In the interim, you can continue to access the current database at http://cxc.harvard.edu/cgi-gen/cda/bibliography
Finally, we have been collecting Chandra-related SPIE papers for a number of years and making them available online. This year we have collaborated with ADS allowing them to link to our repository from their pages.
We are excited about our expanded bibliography services and hope you will find them helpful.
Meet the Archive Operations Team (with a brief history)
The Archive Operations Team ("arcops", for short) is led by Arnold Rots who has been the Archive Astrophysicist since December 1997; he also provides the connections with outside entities, such as other data archives, the Virtual Observatory, the ADS, IAU commissions, FITS committees, ADASS, ADEC, and some of the digitization efforts at the Smithsonian Institution.
Michael McCollough is the second Archive Astrophysicist who has served as Arnold's deputy since April 2003; together they are involved in science support for the Chandra Source Catalog. Mike's predecessor was Stephane Paltani who automated the provisional Data Distribution system, started the bibliography database, and provided an early design for the Chandra Source Catalog. Before Stephane's arrival it was Tomas Girnius who provided during his brief tenure the original implementation of the Provisional Retrieval Interface.
Sherry Winkelman is the Chief Archive Specialist who directs the daily operations of the team, has designed (and implemented) the bibliography database, and, in general, oversees the software development needed for the team's operational activities. Sherry has been with the team since August 1998. She leads a team of three Archive Specialists who all joined the team in 2008; in order of arrival: Glenn Becker, Aaron Watry, and Joan Hagler. Their positions were held in the past by Jed Stamas, Michael Preciado, Emily Blecksmith, Kendra Michaud, Sarah Blecksmith, John Bright, Melissa Cirtain, and Alaine Duffy.
Finally, there is Padmanabhan Ramadurai (Durai for short) who is the database administrator and shares his time between arcops and the CXC Systems Group.
Chandra Source Catalog
The first official release of the Chandra Source Catalog (CSC) is now fully available for use by the astronomical community. The release is accessible publicly through the catalog web site (http://cxc.harvard.edu/csc/), which also contains a wealth of supporting information for prospective catalog users. The catalog production database, which includes information about observations processed to-date during the production phase of the catalog, has been available since October 2008.
Release 1 of the CSC includes 94,688 sources detected in ACIS imaging observations released publicly prior to the start of 2009 (see Figure 29). Only point and compact sources, with observed spatial extents < ~30 arcsec, are included in this release; sources larger than this are not detected by the current catalog algorithms. In general, observations of fields containing highly extended sources are not included in this release. However, if the extended emission is isolated to a single ACIS CCD, then the remainder of the field covered by the other CCDs is included. Multiple observations of the same field are not co-added prior to performing source detection; instead, source detection is performed on each observation individually.
A subsequent release (1.1) is planned for later this year to extend the catalog to include public HRC-I imaging observations, and newly public ACIS observations, but will otherwise retain the same limitations as Release 1.
The CSC is capable of supporting many diverse scientific investigations. However, users should carefully review the "Caveats and Limitations" section of the catalog web site when assessing the efficacy of the catalog for their particular line of enquiry. Since the catalog is constructed from a subset of public pointed Chandra observations, users should be aware that there may be fundamental and significant selection effects that restrict the source content of the catalog and which therefore may limit scientific studies that require an unbiased source sample.
Release 1 of the CSC includes detected sources with fluxes that are at least 3 times greater than their estimated 1σ uncertainties (typically corresponding to about 10 net source counts on-axis and roughly 2030 net source counts off-axis).
The catalog includes numerous raw measurements, as well as scientifically useful source properties derived from the data. These include estimates of the source position measured from each observation in which a source is detected, as well as raw source and PSF extents, and the deconvolved source extent, in several energy bands. Aperture photometry for sources detected in ACIS observations is provided for 5 energy bands broad (0.57.0 keV), ultra-soft (0.20.5 keV), soft (0.51.2 keV), medium (1.22.0 keV), and hard (2.07.0 keV) using several different methods. Band images and exposure maps in FITS format are provided for each source, together with a full-field limiting sensitivity map.
Cross-band (hard, medium, soft) spectral hardness ratios are reported for all detected sources, and absorbed power-law and black-body spectral fits are performed for sources with at least 150 net counts. Source pulse-invariant spectra and spectral response matrices are produced for sources detected in ACIS observations.
Several source variability measures are included, both within a single observation of a source and between multiple observations that include the same source. Intra-observation measures include Kolmogorov-Smirnov and Kuiper test probabilities, and a Gregory-Loredo odds ratio. An optimally binned light curve is produced for each source.
Catalog Statistical Properrties
As part of the official catalog release, a characterization of the statistical properties of the catalog is provided. Preliminary analysis of both simulations and real datasets indicates that the statistical properties of the CSC may be characterized as follows:
- False source rates of << ~1 per observation for exposures ~<50 ks, and ~1 per observation for exposures ~>120 ks;
- 50% completeness (see Figure 30) at broad-band fluxes of ~7 x 10-15 ergs cm-2 s-1 for a ~10 ks observation, improving to ~9 x 10-16 ergs cm-2 s-1 for a ~125 ks observation;
- Positional uncertainties (see Figure 31) of ~<1" (95% confidence) for sources with more than 10 counts, located within 3' of the optical axis, ~<2" for sources with more than 30 counts, within 10', and ~<5" for sources with more than 50 counts, within 15';
- Flux accuracies of better than ~35% (1σ) for sources with more than 30 counts, within 3' of the optical axis, ~30% for sources with more than 50 counts, within 10', and ~25% for sources with more than 100 counts, within 15'.
Data Access and User Documentation
The easiest way to query the CSC is via the CSCview web interface, on the catalog web site. CSCview enables the user to search for sources matching user-supplied constraints for any of the catalog properties, including searching by source position (cone search). The user can select which of the extensive set of catalog parameters they wish to display for matching sources, or can choose to see one of the pre-defined sets of parameters optimized for common queries. Besides displaying the results of a search on the screen, the user may choose to save the search results in a data table. CSCview also provides access for downloading any of the file-based data products that are included in the catalog.
The catalog website (http://cxc.harvard.edu/csc/) is also the place to look for a large bank of user documentation. Sections describe in detail the contents of the catalog, including important caveats and limitations; how to access the catalog; threads that include example catalog searches; and the statistical characterization of the catalog properties, and suggested language for acknowledging the use of the CSC in publications. The user documentation on the catalog website will continue to be improved and extended over the coming months.
What is TGcat?
"TGCat" is a catalog and archive of Chandra data taken with a transmission grating spectrometer the High Energy Transmission Grating (HETG) or the Low Energy Transmission Grating (LETG) in conjunction with one of the spectroscopic readout arrays, ACIS-S or HRC-S. The catalog can be found at http://tgcat.mit.edu/.
Goals & Contents of the Catalog
Our intents are to
- Make grating observations more accessible and visible. There are over 800 observations to date of more than 300 distinct objects utilizing ACIS-S or HRC-S, with HETG or LETG;
- Provide summary products for easy assessment of the observation content and quality;
- Provide analysis-ready counts spectra and response files;
- Provide a web interface for searching, browsing, plotting, and downloading catalog products;
- Start with a simple catalog and enhance as per user requests;
- Provide scripts for easy reprocessing or customized extractions.
There are a few other spectral catalogs of note which we examined for guidance:
- BiRD: XMM/RGS spectral browser (http://xmm.esac.esa.int/BiRD/)
- HotGas: database of Active Galactic Nuclei (http://hotgas. pha.jhu.edu)
- X-Atlas: HETGS stellar spectra (http://cxc.harvard.edu/XATLAS/). (Westbrook, et al. 2008, ApJS, 176, 218)
BiRD is browse-only simple and easy to use catalog providing plots of XMM/RGS spectra. X-Atlas and HotGas are research-topic oriented, with many model-dependent derived products. HotGas is AGN specific, uses CIAO standard products, has some modeling. X-atlas is quite complex, with many derived quantities and both standard and custom products.
TGCat takes an intermediate approach by providing data and research-ready standard products (PHA, ARF, and RMF files), supporting graphical products for easy assessment and selection of data, and by supplying optional scripts for automated or custom reprocessing by users. TGCat does not provide any model-dependent analysis products.
Features of the Catalog
The catalog has a flexible web interface supporting queries by name (SIMBAD or observer-given), object type, coordinates, simple spectral properties (rates and fluxes), observation ID, or by various other criteria such as grating type, detector, or detector read-mode.
Searches can be done either from a table of observation ID's or through a table of unique targets categorized by SIMBAD names and types. The result is a list of basic information with links to summary plots. A very quick preview is given in a pop-up thumbnail spectrum as you move your cursor over the item. Columns are sortable by a click on the heading.
Pre-computed plots and images help you assess the observation; these products are also used to validate the processing. The summary plots include
- counts spectra (combined 1st orders);
- flux spectrm (if HETGS or LETG/ACIS-S; combined 1st orders);
- light curve (and background);
- central field images for zeroth order detail;
- full field image;
- spectral coordinates image, with extraction region;
- order-sorting image.
Further options allow customized plotting of single or multiple orders or of combined observations, with a wide variety of units. Selections may be packaged for download of standard products (PHA, ARF, RMF files). You may also generate and download an ASCII table of the custom plot.
We have taken care in determining the zeroth order centroid the origin of the wavelength scale. For ACIS cases in which the zeroth order was distorted by CCD pileup or was intentionally excluded to reduce telemetry, we use the alternate method of "findzo" (http://space.mit.edu/cxc/analysis/findzo).
Intentionally Omitted Features
We have avoided producing any model-dependent products which rely on scientific judgement or interpretation: there is no modeling or fitting of spectra, no hardness ratios, no color-color plots, no galleries of spectra of similar objects. We have produced a table of count-rates or fluxes (if ACIS) because these can be reliably calculated. (Fluxes are not available for LETG/HRC-S because of the presence of overlapping orders.) Bands were chosen to overlap the Chandra Source Catalog ranges as well as interesting spectral regions.
The Chandra archive is our primary data source; from the "cdaftp" site (ftp://cdaftp.harvard.edu/pub/science/), we download the minimum number of files required to create the basic spectral products.
Data are reprocessed using ISIS/S-Lang scripts which set up and run CIAO tools to make the standard products. ISIS scripts are also used to make the summary plots and tables.
The database management uses MySQL as its backbone. The web-based interactive plotting creates and runs ISIS scripts.
Detailed knowledge of ISIS, S-lang or MySQL are not required to use the catalog. However, the reprocessing scripts are available for users. A top-level function will perform end-to-end processing, starting with events, and ending with the spectrum, responses, and summary plots.
No proprietary software has been used for TGCat.
Example of Reprocessing Using the TGCat Scripts:
The following example set of commands using OBSID 16 will take about 30 minutes from download to data products and summary plots creation:
# slsh script - retrieves minimal set of files from the cdaftp site: > download_obsid 16 # shell script - sets up links required by TGCat ISIS scripts: > setup_obsdir obs_16 # Start ISIS in a ciao-configured shell, and load the processing package: > isis isis> require("tgcat"); % Run the pipeline using the configuration read from a header, use "findzo": isis>run_cfg( "obs_16", 1); isis> exit; # review the summary plots: > display obs_16/summary*.ps &
In a future release, we will provide combined data for single "observations" (defined by sequence number, but probably spanning multiple observation IDs). We will also add extractions for serendipitous sources and for isolated sources in crowded fields. We also intend to provide zeroth order spectra and responses.
We will be adding more convenience functions to the processing scripts, such as to support easy time-slicing, or for customized regions.
We also encourage user-requests (email firstname.lastname@example.org) and would especially like to hear of usage scenarios in your research.
A number of people have been involved in TGCat since we started work in August 2007. First, thanks to Claude Canizares who suggested that we think about creating a grating catalog as a part of the Chandra legacy. And next, in alphabetical order, thanks to John E. Davis, John C. Houck, Herman L. Marshall, and Doug Morgan.
Cycle 10 Peer Review
The observations approved for Chandra's 10th observing cycle are now in full swing and the Cycle 11 Call for Proposals was released on 15 December 2008. Cycle 9 observations are very close to completion and Cycle 10 observations began in the Fall 2008. The substantial overlap of the two cycles allows us to efficiently fill the observing schedule.
The Cycle 10 observing and research program was selected as usual, following the recommendations of the peer review panels. The peer review was held 17-20 June 2008 at the Hilton Boston Logan Airport. More than 100 reviewers from all over the world attended the review, sitting on 14 panels to discuss 643 submitted proposals (Figure 37). The Target Lists and Schedules area of our website provides lists of the various types of approved programs, including abstracts. The peer review panel organization is shown in Table 1
|Table 1: Panel Organization|
|Panels 1, 2||Normal Stars, WD, Planetary Systems and Misc|
|Panels 3, 4||SN, SNR + Isolated NS|
|Panels 5,6,7||WD Binaries + CVs, BH and NS Binaries, Galaxies: Populations|
|Panels 8,9,10||Galaxies: Diffuse Emission, Clusters of Galaxies|
|Panels 11,12,13||AGN, Extragalactic Surveys|
|Big Project Panel|
|LP and VLP Propoosals|
The over-subscription rate in terms of observing time for Cycle 10 was 5.3, similar to that in previous cycles (Figure 38), with the total time request being ~ 89 Msecs, again similar to past cycles (Figure 39). As is our standard procedure, all proposals were reviewed and graded by the topical panels, based primarily upon their scientific merit, across all proposal types. The topical panels produced a rank-ordered list along with detailed recommendations for individual proposals where relevant. A report was drafted for each proposal by one/two members of a panel and reviewed by the Deputy panel chair before being delivered to the CXC. The topical panels were allotted Chandra time to cover the allocation of time for GO observing proposals based upon the demand for time in that panel. Other allocations made to each panel were: joint time, Fast and Very Fast TOOs, time constrained observations in each of 3 classes and money to fund archive and theory proposals. Many of these allocations are affected by small number statistics in individual panels so allocations were based on the full peer review over-subscription ratio. Panel allocations were modified, either in real time during the review or after its completion, transferring unused allocations from one panel to other panels which requested more.
Large (LP) and Very Large Projects (VLP) were discussed by the topical panels and ranked along with the other proposals. The topical panels' recommendations were recorded and passed to the Big Project Panel (BPP). The BPP discussed the LPs and VLPs and generated a rank-ordered list. BPP panelists updated review reports, as needed, both at the review and remotely over the following 2 weeks. The schedule for the BPP included time for reading and for meeting with appropriate panel members to allow coordination for each subject area. The BPP meeting extended into Friday morning to allow for additional discussion and a consensus on the final rank-ordered list to be reached.
The resulting observing and research program for Cycle 10 was posted on the CXC website three weeks later, 11 July 2008, following detailed checks by CXC staff and approval by the Selection Official (CXC Director). All peer review reports were reviewed by CXC staff for clarity and consistency with the recommended target list. Letters informing the PIs of the results, budget information (when appropriate) and providing a report from the peer review were e-mailed to each PI in August.
Joint Time Allocation
Chandra time was also allocated to several joint programs by the proposal review processes of Hubble and XMM-Newton (2 proposals in each case). The Spitzer joint program was not available in Cycle 10 due to the satellite's transition to the warm mission.The Chandra review accepted joint proposals with time allocated on: Hubble (14), XMM-Newton (2), NRAO (7), NOAO (6) and RXTE (2).
As observers are aware, the biggest challenge to efficient scheduling of Chandra observations is in regulating the temperature of the various satellite components (see POG Section 3.3.3). In Cycle 9 we instituted a classification scheme for constrained observations which accounts for the difficulty of scheduling a given observation (CfP Section 5.2.8). Each class was allocated an annual quota based on our experience in previous cycles. The same classification scheme was used in Cycle 10. There was a large demand for constrained time so that not all passing-ranked proposals which requested time constrained observations could be approved. Effort was made to ensure that the limited number of constrained observations were allocated to the highest-ranked proposals review-wide. Detailed discussions were carried out with panel chairs to record the priorities of their panels should more constrained observations become available. Any uncertainty concerning priorities encountered during the final decision process was discussed with the relevant panel chairs before the recommended target list was finalized. Please note that, as with Cycle 9, the most over-subscribed class was: "EASY" while "AVERAGE" was only marginally over-subscribed. In practice we combined these two classes in order to determine which observations should be allocated time. The same 3 classes will be retained so as to ensure a broad distribution in the requested constraints. We urge proposers to specify their constraints as needed by the science rather than ensuring they are "EASY".
Large and Very Large Projects
For the first time in Cycle 10, the full 6 Msecs of observing time available for Large and Very Large Projects (LPs, VLPs) was combined so that projects of both types competed for the full amount. In principle this allows projects requesting as much as 6 Msecs to be proposed, and approved. In practice the Big Project Panel recommended 15 LPs totalling 5.82 Msecs and no VLPs. The Large Project type has long been the most highly over-subscribed, a factor of >8 since Cycle 4 and close to 10 in Cycle 10. The combination of the two types results in an effective over-subscription of 6.5 for LPs, much closer to the review average of 5.3. The over-subscription for VLPs, though, is effectively infinite! In discussion with the Chandra Users' Committee, the process in which the two types are combined will be reviewed in advance of the release of the Cycle 12 Call for Proposals, based on the results of two peer reviews and experience with scheduling the resulting observing programs.
PIs of proposals with US collaborators were invited to submit a Cost Proposal, due in Sept. 2008 at SAO. As in past cycles, each project was allocated a "fair share" budget based on their observing program, as described in CfP Section 8.4. For the first time in Cycle 10, cost proposals requesting budgets at or lower than the allocated "fair share" budget were reviewed internally while those requesting more (8% of the cost proposals) were subject to an external review by a subset of the science peer reviewers. For these, final budgets were allocated based on the recommendations of the external review. The results were announced in early December, in good time for the official start of Cycle 10 on 1 Jan. 2009. Cycle 10 projects for which observations were started before mid-November 2008 were processed as early as possible, allowing their grants to be issued in a timely manner.
Statistics on the results of the peer review can be found on our website: under "Target Lists and Schedules": select the "Statistics" link for a given cycle. We present a subset of these statistics here. Figure 40 displays the effective over-subscription rate for each proposal type as a function of cycle. Figures 41, 42 show the percentage of time allocated to each science category and to each instrument combination. Finally there is a list of proposals according to their country of origin.
Requested Approved Country #Prop Time*(ksec) #Prop Time*(ksec) ------------------------------------------------------------ USA 492 67173.60 151 13147.80 Foreign 151 22065.60 48 5085.70 Requested Approved Country #Prop Time(ksec) #Prop Time(ksec) ------------------------------------------------------------ ARGENTINA 1 57.00 AUSTRALIA 7 817.30 3 576.30 BELGIUM 2 270.00 BRAZIL 1 60.00 CANADA 13 3526.50 4 708.20 CHINA 1 50.00 FRANCE 6 470.00 3 270.00 GERMANY 19 1841.00 5 240.00 GREECE 2 175.00 INDIA 1 82.40 ITALY 25 3459.00 8 820.00 JAPAN 9 1069.00 2 190.00 NETH 13 1314.00 7 674.00 POLAND 1 30.00 RUSSIA 2 70.00 SPAIN 7 770.00 1 20.00 SWITZ 4 427.30 1 60.00 TAIWAN 2 294.00 UK 34 7083.10 14 1527.20 USA 492 67173.60 151 13147.80 VENEZUELA 1 200.00 ------------------------------------------------------------ 643 89239.20 199 18233.50 *Note: Numbers quoted here do not allow for the probability of triggering TOOs
Upcoming Chandra Related Meetings
Check our website for details: http://cxc.harvard.edu/
Workshop: Supernova Remnants and Pulsar Wind Nebulae
July 8-10, 2009
10 Years of Chandra
Chandra Calibration Review
Einstein Fellows Symposium
Einstein Postdoctoral Fellowship Program
The Chandra Postdoctoral Fellowship program has now had 11 groups of Fellows: http://cxc.harvard.edu/fellows/fellowslist.html Many of the Newsletter readership may have enjoyed the exciting work they do by attending one of the annual Chandra Fellows Symposia.
Last summer, however, NASA reorganized its Postdoctoral Fellowship programs. The Chandra program was joined with the Fermi program to become the Einstein program, which was broadened to include science related to the Physics of the Cosmos program: http://nasascience. nasa.gov/programs/physics-of-the-cosmos In the call for proposals for the first Einstein Fellowship competition last fall, the missions were summarized as follows: "These include high energy astrophysics relevant to the Chandra, Fermi (formerly GLAST), XMM-Newton, INTEGRAL, and IXO (formerly Constellation-X) missions, cosmological investigations relevant to the Planck and JDEM missions, and gravitational astrophysics relevant to the LISA mission."
Ten Fellowships will now be given out for the Einstein program. In November, 2008 a record number of 156 applications were received for the first competition of the program. Once again, we invite you to enjoy the work of the Einstein Fellows at the first annual Einstein Fellows symposium in the fall 2009.
Einstein Fellows 2009
|Host Institution||PhD Institution|
|Bogdanovic, Tamara||Maryland||Penn State|
|Lehmer, Bret||Johns Hopkins||Penn State|
|Ofek, Eran||CalTech||Tel Aviv|
Education and Public Outreach Proposals Selected in Cycle 10Kathy Lestition
The Cycle 10 Chandra EPO Peer Review, conducted by the CXC, was held in Cambridge MA on Dec. 3-5, 2008. A panel representing science, education, museum, Forum, and NASA mission and management perspectives reviewed 10 proposals. Seven individual and 3 institutional proposals were submitted. Three individual and 2 institutional proposals were selected for funding. An overview of the selected proposals by type follows, alphabetically in order of PI last name.
The Making of a Star and It's Entourage: A Planetarium Show About the Formation of Stars and Planetary Systems
Science PI: Prof. Jeffrey S. Bary, Colgate University, email@example.com
EPO Co-I: Joe Eakin, Ho Tung Visualization Lab, Colgate University
Education Partner: Ho Tung Visualization Lab, Colgate University
In collaboration with a unique program at Colgate University which integrates the Visualization Lab into course content, this proposal will recruit approximately 20 Colgate University undergraduates from a variety of academic specialities (music, theater, graphic arts & design, physics & astronomy, history) to participate in aspects of the production of a high-quality planetarium show that align with their areas of academic expertise. The content is related to the PI's research. Topics will include the nature of the scientific endeavor and modern discovery, the processes by which planetary systems form, and our conception of our place in the universe. This rural area of central New York is underserved by NASA resources and the show will be an introduction to NASA science for students from the local school districts, other Colgate undergraduates, and the general public. This show will be the inaugural product for the recently opened, state of the art visualization lab and sound studio, and full-dome planetarium theater equipped with Digistar 3 projector. The EPO Co-I is an experienced content developer and oversees the Viz lab integration program. The show will be distributed to other planetaria.
Black Holes - A New Penn State Professional Development Workshop for Science Teachers
Science PI: Dr. William N. Brandt, Penn State University, firstname.lastname@example.org
EPO Co-I: Dr. Christopher Palma, Penn State University, email@example.com
Education Partner: Pennsylvania Space Grant Consortium
This proposal will fund the participation of teachers recruited from high poverty, underserved areas of both rural and urban Pennsylvania in a new professional development workshop focused on the topic of black holes. The workshop was developed based on focus group evaluations from participants of past workshops and the content was pilot tested and revised. In addition to the workshop, teachers will be offered a more sustained, long-term experience through a series of follow-up teleconferences in the school year following their summer participation. The workshop will utilize an available set of tested, standardsaligned NASA activities on black holes. The workshop is offered as a graduate credit-bearing course.
Addressing the Nature of Science Through a Telescope Loaner Program for Teachers
Science PI: Prof. Craig Sarazin, University of Virginia, firstname.lastname@example.org
EPO Co-I: Dr. Edward Murphy, University of Virginia, email@example.com Education Partner: University of Virginia Astronomy Department
The goal of this program is to address the nature of science, astronomy, and the space science components of the Virginia Standards of Learning through a telescope loaner program and associated educational materials for teachers. The proposal builds on an earlier program utilizing these telescopes with teachers, developed by Co-I Murphy and Randy Bell, an Associate Professor at the U. VA Curry School of Education. Feedback indicated a lack of equipment at schools to enable the teachers to transmit their astronomy knowledge to students. This proposal utilizes 10 working Meade LX-10 8-inch Schmidt-Cassegrain telescopes recently retired by the University of Virginia Astronomy Department and made available to this program at no cost. After training, teachers will be able to check out a telescope for a period of one month to use at their school in night observing and daytime education activities. The science content will draw heavily from the research of NASA missions. Teachers will receive development credits for participation.
Building Partnerships Through "Kids Capture Their Universe"
Science PI: Dr. Deepto Chakrabarty, MIT Kavli Institute for Astrophysics and Space Research, firstname.lastname@example.org. edu
EPO Co-I: Dr. Irene Porro, MIT Kavli Institute for Astrophysics and Space Research. email@example.com
Education Partners: - Citizen Schools - Science Education Department, Smithsonian Astrophysical Observatory (SAO)
The purpose of this proposal is to promote the dissemination and sustainability of the "Kids Capture Their Universe" (KCU) program. The KCU is at present successfully operating at 7 Citizen School sites. This proposal will add 10 additional out-of-school-time (OST) organizations across Massachusetts, particularly those serving populations underserved and underrepresented in STEM. The new OST organizations will develop partnerships with volunteers from local astronomy and space science communities to present an after-school program. The intent is to provide sustainability through the development of a pool of both astronomy content experts and OST centers with a common vision of the value of after-school science programs. The institutional team member scientists as well as other current volunteers are the core group of astronomy experts who will initiate partnerships with the new OST organizations and participate in the preparation of the training workshops. They will also be actively involved in recruitment of additional volunteer experts. The KCU curriculum utilizes the MicroObservatory robotic telescope network to provide concrete astronomy learning opportunities.
Touring a Universe of Black Holes: A WWT Educational Package
Science PI: Dr. Martin Elvis, Smithsonian Astrophysical Observatory, firstname.lastname@example.org
EPO Co-I: Mary Dussault, Science Education Department, Harvard-Smithsonian Center for Astrophysics (CfA)
Education Partner: Science Education Department, CfA
With funding from NSF and NASA, the Science Education Department at the CfA is creating a national traveling exhibit, "Black Holes: Space Warps & Time Twists" that will tour the US for 3 years starting in June 2009. A cutting edge feature of the exhibit will be networked exhibit work stations where visitors will be able to create a personalized exhibit website through the use of swipe cards. The web content authoring system supports on-going visitor engagement beyond the walls of the museum, and connects the visitor experience to the immense reservoir of on-line resources. The newly emerged World Wide Telescope (WWT) technology is a logical extension of this forwardlooking exhibit technology. This proposal will develop, as an integral part of the personalized exhibit web site option, an exhibit-specific accessible portal to the WWT that will allow visitors to extend their explorations of the exhibit content through the WWT's visualization software environment. The exhibit-tailored package within WWT will contain supplementary education materials that integrate WWT content with the exhibit museum education programs. The grant will also support direct educator and scientist involvement at the first 4 museum venues in the use of the science from the exhibit and the WWT in education programs.
Chandra in IYA2009
The International Year of Astronomy 2009 (IYA2009) was conceived to honor the 400th anniversary of the first use of an astronomical telescope by Galileo Galilei in 1609, and has evolved into an extensive series of worldwide programs. Sponsored by the International Astronomical Union (IAU) and endorsed by the U.S. House of Representatives, UNESCO and the United Nations, IYA2009 aims to stimulate worldwide interest in astronomy and science, especially among young people and underserved populations. More than 135 countries and agencies are participating in this important global event. IYA2009's purpose is about more than just celebrating astronomy achievements during a single year: its goal is to build sustainable astronomy education and outreach programs and partnerships that will continue on into the future.
Chandra is heavily involved with several IYA2009 activities (for a full list of US and international activities, see www.astronomy2009.us and www.astronomy2009.org). Specifically, Chandra will be featured in the "100 Hours of Astronomy" webcast, "365 Days of Astronomy" podcasts, the Great Observatories image unveilings to museums, and more.
One of the IYA2009 efforts being led out of the Chandra X-ray Center is the "From Earth to the Universe" project (www.fromearthtotheuniverse.org ). FETTU is a major project of both the US and global efforts for the IYA2009. With images taken from both ground- and space-based telescopes (including Chandra, of course), FETTU showcases the incredible variety of astronomical objects that are known to exist: planets, comets, stars, nebulae, galaxies, clusters, and more.
FETTU will be shown in non-traditional public venues such as parks and gardens, shopping malls, metro stations and airports in major cities across the world. The FETTU images have been selected for their stunning beauty to engage members of the general public who might normally ignore or avoid astronomy. With short, but informative captions on each panel, the goal is introduce some basics of the science once an individual has been drawn to the image. In the US, FETTU is being sponsored by NASA and will appear in semi-permanent installations in Atlanta and Chicago later this spring. A traveling version of FETTU will begin in the Tucson airport in late February before moving to Memphis in April. Several editions of FETTU will be appearing in the San Francisco area beginning in May, thanks to NASA's Lunar Science Institute, and the NASA Student Ambassador program is facilitating a FETTU exhibit in Madison, Wisc. More FETTU locations are being planned across the US and an enhanced schedule is being developed.
With NASA support, FETTU panels for the visually impaired are being prepared. The caption material for all of the images in the US collection of 50 images is available in both English and Spanish.
"It's great to see FETTU taking shape in the United States thanks, in large part, to NASA," said Kim Kowal Arcand of the Chandra X-ray Center and principal investigator for the NASA FETTU grant. "It's also amazing to see how it has taken off around the world."
With 2009 underway, FETTU is already being showcased in a variety of formats both physically and digitally in over 40 countries around the globe. These worldwide exhibits have been funded through a variety of local resources and are organized by each individual location. For a full list of known FETTU exhibits both in the US and internationally - visit http://www.fromearthtotheuniverse. org/table_events.php
While there is only one official year to celebrate astronomy, the goal is that the impact of FETTU and all of the other IYA2009 activities will extend far beyond that. By exposing the public to the wonders that Chandra and other telescopes have discovered, the hope is that it will create a lasting impression and generate further interest in astronomy and all science.
Enjoy 2 examples of the exhibits (Figures 44 and 45).
International X-ray Observatory Update
As this newsletter article is being written, the IXO team, which includes many of you readers, is working on science white papers for the upcoming decadal survey. By the time you read this, those white papers will be completed and the Science Frontiers survey panel members will be reading and evaluating those papers. A big THANKS to all of you for your recent efforts on these papers, and for your help over the years in shaping the IXO into what it has become. The final submitted white papers build on the papers and presentations that you have crafted over the last several years.
The IXO team recently answered the 'notice of intent' request from the decadal, along with 171 other projects. The full list of projects can be seen on the ASTRO 2010 web site. The next stages of input into the decadal process are likely to be a town hall meeting in the Cambridge area in late March, followed by a submission from the project team on the observatory due April 1. As you can see from the rapid schedule, the decadal process is in full swing!
The first meeting of the combined IXO teams (formerly the Con-X and XEUS teams) was held in late August 2008 at GSFC, and was quickly followed in September 2008 by a meeting at MPE in Garching attended by over 150 people. The presentations from both meetings are posted on the revamped IXO web site, ixo.gsfc.nasa.gov. A key milestone described at both meetings was the technology assessments led separately by NASA and ESA, which converged on a consistent and robust mission design. This design retains the Con-X baseline instrument set (the calorimeter, gratings, and hard x-ray detector) but includes additional instruments from the XEUS baseline. The new instruments include a wide field imager (18 x 18 arcmin FOV), a polarimeter, and a high counting rate spectrometer. The next meeting of the IXO teams will also have occurred by the time you read this article, and is in late January in Cambridge, MA. Despite the likely chilly weather over 200 attendees have registered. This meeting will concentrate on the white papers to be submitted to the decadal science panels by Feb 15.
The IXO was well represented at several special sessions at the Jan. 2009 AAS meeting. The 40 posters at the special IXO poster sessions are now on line at the IXO web site. The special oral session in the main hall, which included presentations from IXO, EXIST, and Gen-X was also well attended.
Lastly, please join us in welcoming Randall Smith to the IXO team at SAO, and Rita Sambruna to the IXO team at GSFC.
Chandra Users' Committee Membership List
The Users' Committee represents the larger astronomical community. If you have concerns about Chandra, contact one of the members listed below.
|Elizabeth Blanton||Boston Univ.||email@example.com|
|Martin Laming (Chair)||NRLfirstname.lastname@example.org|
|Jon Miller||U. Michiganemail@example.com|
|Luisa Rebull||Spitzer Science Centerfirstname.lastname@example.org|
|Ex Officio, Non-Voting|
|Jaya Bajpayee||NASA HQemail@example.com|
|Wilt Sanders||NASA HQfirstname.lastname@example.org|
|Allyn Tennant||NASA/MSFC, Project Scienceemail@example.com|
|Belinda Wilkes||CXC Director's Officefirstname.lastname@example.org|
|Paul Green||CXC Director's Officeemail@example.com|
DG Tau: Energetic Jets from a Budding Solar System
The young star, named DG Tau, is located in the Taurus star-forming region, about 450 light years from Earth. The bright source of X-rays in the middle of the image (Figure 46) is DG Tau and the jet runs from the top left to the bottom right, extending to about 70 billion miles away from the star, or about 700 times the Earth-Sun separation.
A detailed analysis of this image, led by Manuel Guedel of the Institute of Astronomy, ETH Zuerich in Switzerland, shows that the counter jet (top-left) has, on average, higher energy X-rays than the forward jet (bottom-right). The likely explanation is that some of the lower energy X-rays in the counter jet are absorbed by a disk around DG Tau, as shown in the accompanying illustration (right graphic), showing the star, disk and the inner regions of the jets.
Highly energetic X-rays are also detected from the young star, partially absorbed by streams of material flowing from the disk onto the star. The disk itself is much too cool to be detected by Chandra. Note that the faint vertical feature below the star does not show evidence for an additional jet, but is a chance alignment of four photons.
The effects of the jet on its surroundings may be significant. Other researchers have previously suggested that X-rays from a typical young star can significantly affect the properties of its surrounding disk, by heating it and creating charged particles by stripping electrons off atoms (a process called ionization). These X-rays will strike the disk at a low angle, mitigating their effects. In the case of the jets from DG Tau, the combined X-ray power in the jet is similar to that of a young star with relatively modest X-ray brightness, but X-rays from the jet have the advantage of striking the disk much more directly from above and below.
Guedel and colleagues argue that powerful X-ray jets might develop at some stage during the evolution of most young stars. They could, for example, have existed during the early stages of the solar system. DG Tau has about the same mass as the Sun, but is much younger with an age of about one million years, rather than about 4.5 billion years. Since it is surrounded by a disk where planets may be forming, this new Chandra image suggests that the early Earth and its environment may have been bathed in X-rays from a jet like DG Tau's. Although it is unknown if such X-rays would have had a significant impact on the forming Earth, it is possible that they did more good than harm. By ionizing the disk the X-rays may have generated turbulence, which could have had a substantial effect on the orbit of the young Earth, possibly helping to prevent it from making a disastrous plunge into the Sun. Furthermore, X-ray irradiation of disks may also be important in the production of complex molecules in the disk that will later end up on the forming planets.
The new X-ray observations of X-ray jets add new features to the already complex story of star and planet formation. The ionization and heating power of the X-rays from jets will have to be included in future model calculations that will help scientists understand the physical evolution and chemical processing of environments that eventually lead to planets like those in our solar system.
Important Dates for Chandra
- Proposals Due
- March 17, 2009
- Users' Committee Meeting
- April 6, 2009
- Cycle 11 Peer Review
- June 23-26, 2009
- Workshop (SNRs and Pulsar Wind Nebulae)
- July 8-10, 2009
- 10 Years of Chandra Symposium
- September 22-25, 2009
- Cycle 11 Budgets Due
- September 17, 2009
- Cycle 11 EPO Proposals: Electronic
- October 23, 2009
- Cycle 11 EPO Proposals: Hardcopy
- October 28, 2009
- Einstein Fellows Symposium
- Fall, 2009
- Users' Committee Meeting
- Fall, 2009
- Einstein Fellowship Applications Due
- Oct/Nov, 2009
- Cycle 11 EPO Peer Review
- December, 2009
- Cycle 11 Observations Start
- December, 2009
- Cycle 12 Call for Proposals
- December 2009