Symposium Proceedings

Extragalactic Diffuse Emission and Surveys

LBG, LAE & AGN at z$\sim$3 in MUSYC-ECDFS

Harold Francke (Universidad de Chile), Eric Gawiser, Shanil Virani, (Yale Univ.), Ezequiel Treister (Universidad de Chile), Meg Urry (Yale Univ.)

The E-CDFS field is the largest Chandra survey ever conducted at its depth ($\sim$0.3 square degrees and 228 ks), and is also one of the 4 fields included in the MUltiwavelength Survey by Yale/Chile (MUSYC; Gawiser et al. 2005, astro-ph/0509202). The broad coverage of the survey (UBVRIzJHK+NB5000) is especially suited for selecting objects at specific redshifts. Using x-ray, UVR and BV+NB colors, we have selected AGN, LBG (Lyman Break Galaxies) and LAE (Lyman Alpha Emitters) at z$\sim$3. We present results on the demographics of this set of protogalaxies, including estimates of the fraction of LBGs and LAEs that contain AGN, the joint x-ray and optical selection of AGN at this redshift, and the clustering amplitude of these sources.


Searching for Type-2 QSOs in Chandra/SDSS Fields

Ioannis Georgantopoulos, Athanasios Akylas (National Observatory of Athens)

We are searching for type-2 (narrow-line) QSO candidates among the Chandra XASSIST sources which have been spectroscopically identified in the Sloan Digital Sky Survey. Candidates are selected having a) column density $N_H>10^{22} cm^{-2}$ as derived from the hardness ratios b) luminosity $L_x>10^{44} erg ~s^{-1}$. Our sample consists of 23 type-2 QSO candidates. Detailed X-ray spectral analysis with XSPEC shows that only three sources present indeed high, $N_H>10^{22} cm^{-2}$, column densities. All three have broad lines in their optical spectra and thus no source can be classified as a bona-fide type-2 QSO at least according to the strict optical classification. However, we cannot rule out the possibility that a number of type-2 QSO reside among fainter optical sources which have no SDSS optical spectroscopy.

[PDF of the poster]

X-ray Luminous High Redshift Quasars from the ChaMP

Paul Green (SAO), John Silverman (MPE), Wayne Barkhouse (UIUC), Dong-Woo Kim, Minsun Kim, Belinda Wilkes, Amy Mossman (SAO), Harvey Tananbaum (SAO)

The space density of luminous optically-selected quasars peaked 2-3 Gyr after the Big Bang, but we know that much of accretion onto supermassive black holes is obscured, perhaps even more so in the early Universe. Both the intrinsic physical properties of high redshift quasars and their population statistics are of interest, but few X-ray-selected examples are known to date. The Chandra Multiwavelength Project provides a significant number of high redshift (z$>$3) X-ray selected quasars. We present new results on spectral energy distributions and evolution of these objects, including a revised X-ray luminosity function that maximizes the sample size using a large compilation of surveys. Since at low redshifts we know that low and high luminosity objects evolve very differently, we constrain luminosity-dependent density evolution models using maximum likelihood model fits.


Intensity of the Unresolved Cosmic X-ray Background for 2-7 keV with Chandra

Ryan Hickox, Maxim Markevitch, Christine Jones (Harvard-Smithsonian Center for Astrophysics)

We will present results for the intensity of the unresolved cosmic X-ray background from 2 to 7 keV, using the Chandra Deep Fields (CDF) North and South. The X-ray surface brightness of these fields, excluding point and diffuse sources, is measured for observations over several epochs. We use detailed modeling of the ACIS-I instrumental background and careful flare removal to eliminate the non-sky components of the observed background. We calculate the resulting fraction of the XRB that remains unresolved at Chandra fluxes below $\sim$$10^{-16}$ ergs cm$^{-2}$ s$^{-1}$.

The following is the poem which Ryan wrote for the one-minute poster presentation session.

The cosmic X-ray background, it has recently been shown
Comes from mostly AGN and sources that are known

And so it seems the problem is quite close to being solved
But still there is a bit of flux that remains unresolved

Using data from the Chandra Deep Fields North and South, of course
We find the unresolved flux, excluding every source

The hardest part is taking care of backgrounds in the ACIS
But after that subtraction, still some flux remains, in traces

Quite significant a signal, it is larger than you'd guess
From a quick extrapolation of the known logN/logS

And so there still remains an X-ray background mystery
Are there lots of fainter sources? are they starburst galaxies?

If you'd like hear about all this analysis and more
Then please do come along by poster number 4.4

The Chandra/SWIRE Multi-wavelength Survey

Roy Kilgard, Belinda Wilkes (SAO), Alberto Franceschini (Universita di Padova), Dong-Woo Kim, Minsun Kim (SAO), Carol Lonsdale (Cal Tech), Frazer Owen (NRAO), Maria Polletta (Cal Tech), Brian Siana (Spitzer Science Center), Harding Smith (UCSD), Jason Surace (Cal Tech)

The Spitzer Wide-area Infrared Extra-galactic Survey (SWIRE) is designed to study the structure, evolution and environments of AGN, starbursts, and ellipsoids over the same spatial volume out to z $>$ 2.5. We have completed medium depth (70 ksecs), Chandra ACIS-I, X-ray observations in the northern Lockman Hole SWIRE Field, covering 0.6 deg$^2$ for which deep observations are available in all seven Spitzer bands, optical and near-IR as well as extremely deep VLA 20cm data. We find 812 X-ray sources, of which 762 have counterparts in the Spitzer observations. 15 X-ray sources have sufficient counts to allow X-ray spectral fitting. We present preliminary results from this survey, including the multi-wavelength properties of the X-ray sources and resulting classifications and redshift estimation. We also discuss the highly obscured luminous AGN population, most of which show no detectable AGN characteristics in their optical spectra, and report the discovery of two high-redshift, luminous quasars with highly obscured X-ray and optical emission.

ChaMP Normal Galaxies at Intermediate Redshift

Dong-Woo Kim, Wayne Barkhouse, Paul Green, Eric Schlegel (SAO), John Silverman (MPE) Harvey Tananbaum, Belinda Wilkes (SAO), Encarni Colmenero (SAAO), Minsun Kim, Tom Aldcroft, Craig Anderson (SAO) ChaMP Collaboration

We have investigated 136 Chandra extragalactic sources without broad emission lines, including 93 NELG and 43 ALG. Based on fX/fO, LX , X-ray spectral hardness and optical emission line diagnostics, we have conservatively classified 36 normal galaxies (20 spirals and 16 ellipticals) and 71 AGNs. Their redshift ranges from 0.01 to 1.2, while normal galaxies are at z=0.01-0.3. Our sample galaxies appear to share similar characteristics with local galaxies in terms of X-ray luminosities and spectral properties, as expected from the X-ray binary populations and the hot ISM. In conjunction with normal galaxies found in other surveys, we found no statistically significant evolution in LX/LB, within the limited z range (< 0.1). We have built our log(N)-log(S) relationship of normal galaxies in the flux range, $fX
(0.5-8.0) = 10^{-15} - 10^{-13}$ erg s-1 cm-2, after correcting completeness by a series of simulations. The best-fit slope is -1.5 for both S and B energy bands, which is considerably steeper than that of AGN-dominated cosmic background sources at faint fluxes ($fX < 10^{-14}$ erg s-1 cm-2, i.e., below the break), but slightly flatter than the previous estimate, indicating normal galaxies will exceed in number over the AGN population at $fX < 10^{-18}$ erg s-1 cm-2 (an order of magnitude lower than the previous estimate). We have also built an X-ray luminosity function of normal galaxies in the luminosity range of $LX = 5 x 10^{39} - 10^{42}$ erg s-1, which is consistent with other survey results.

A group of NELGs (most of them with $fX/fO>0.1$) appear to be heavily obscured in X-rays, i.e., a typical type 2 AGN. After correcting intrinsic absorption, their X-ray luminosities could be $LX > 10^{44}$ erg s-1, making them Type 2 quasar candidates. While most X-ray luminous ALGs (XBONG candidates) do not appear to be significantly absorbed, we found two heavily obscured objects, which could be as luminous as an unobscured broad-line quasar. Among 43 ALGs, we found two E+A galaxy candidates with strong Balmer absorption lines, but no [OII] line. The X-ray spectra of both galaxies are soft and one of them has a nearby close companion galaxy, supporting the merger/interaction scenario rather than the dusty starburst hypothesis.

Chandra Multiwavelength Project (ChaMP) X-ray Point Source Catalog

Minsun Kim, Dong-Woo Kim (SAO), Wayne A. Barkhouse (UIUC), Nancy R. Evans, Paul J. Green, Eunhyeuk Kim (SAO), Myung Gyoon Lee (SNU), Amy E. Mossman (SAO), John D. Silverman (MPE), Harvey D. Tananbaum, Belinda J. Wilkes (SAO), ChaMP Collaboration

We present the Chandra Multiwavelength Projects (ChaMP) X-ray point source catalog with $\sim 6,800$ X-ray sources detected in 149 Chandra observations covering $\sim 10~deg^{2}$.The exposure time of our sample ranges up to $\sim 120$ ksec, corresponding to the X-ray flux limit of $f_{0.5-8.0}=9\times10^{-16}~erg~cm^{-2}~sec^{-1}$. The ChaMP catalog includes X-ray photometric data in 8 different energy bands as well as X-ray spectral hardness ratio and colors. To quantitatively assess those parameters, we have performed extensive simulations.We present a set of empirical equations in a few interesting confidence levels: the flux limit as a function of effective exposure time; the positional uncertainty and the false source detection rate as a function of source counts and off-axis angle.

[PDF of the poster]

Chandra Multiwavelength Project (ChaMP) X-ray Point Source Number Counts Relations

Minsun Kim, Dong-Woo Kim (SAO), Wayne A. Barkhouse (UIUC), Nancy R. Evans, Paul J. Green, Eunhyeuk Kim (SAO), Myung Gyoon Lee (SNU), Amy E. Mossman (SAO), John D. Silverman (MPE), Harvey D. Tananbaum (SAO), Belinda J. Wilkes (SAO), ChaMP Collaboration

We present the ChaMP logN-logS relations in the multiple X-ray energy bands. We have used $\sim$5,500 X-ray sources detected from 130 ChaMP fields covering $\sim$9.3 deg$^2$ in sky area. To correct the incompleteness and to determine sky coverage area, we have performed extensive simulations. The number count relations are fitted by a broken power law in differential number count spaces and fitting results agree with previous studies in 1 sigma error range. We also present the simultaneous fitting results of ChaMP and CDFs data. The best-fit parameters are $Gamma_{faint}=1.50^{+0.05}_{-0.07}$, $Gamma_{bright}=2.36^{+0.11}_{-0.12}$, and $S_{b}=6.63\times{10^{-15}}^{+1.28}_{-1.59}$ in the 0.5-2.0 keV band. In the 2.0-8.0keV band, $Gamma_{faint}=1.59^{+0.12}_{-0.08}$, $Gamma_{bright}=2.51^{+0.28}_{-0.09}$, and $S_{b}=12.62\times{10^{-15}}^{+7.01}_{-1.85}$. These number count relations cover very large flux ranges, $f_{0.5-2.0}=3\times10^{-17}~10^{-12}$ and $f_{2.0-8.0}=2\times10^{-16}~10^{-11}$ in cgs units, with the smallest statistical errors yet reported in any survey.

[PDF of the poster]

Statistical Properties of Intermediate-redshift Off-nuclear X-ray Sources in the Chandra Deep Fields

Bret Lehmer, Niel Brandt (PSU), Ann Hornschemeier (Goddard), Franz Bauer (Columbia), Don Schneider, Aaron Steffen (PSU)

We statistically analyze a population of intermediate-redshift (z $\sim$ 0.05-0.3) off-nuclear X-ray sources located within the optical emission of optically-bright galaxies in the Great Observatories Origins Deep Survey and Galaxy Evolution from Morphology and SEDs fields. A total of 19 off-nuclear sources are classified using deep Chandra exposures from the Chandra Deep Field-North, Chandra Deep Field-South, and Extended Chandra Deep Field-South; ten of these sources are newly identified. This sample improves the source statistics for intermediate-redshift off-nuclear sources with 0.5-2.0 keV luminosities L(0.5-2.0 keV) $>\sim
10^{39.5}$ erg s-1, and significant new constraints are placed on the redshift evolution of the frequency of incidence for off-nuclear sources located in field galaxies. We find that the fraction of intermediate-redshift galaxies containing an off-nuclear source is statistically consistent with that observed for ultraluminous X-ray sources in the local universe over L(0.5-2.0 keV) $\sim 10^{39-40.5}$ erg s-1.

[PDF of the poster]

Angular Structures of the X-ray Sources in the Extended Chandra Deep Field-South

Takamitsu Miyaji (Carnegie Mellon Univ.), Roberto Gilli (INAF-Osservatorio Astrofisico di Arcetri), Bret Lehmer, Niel Brandt (Penn State Univ.), Anton Koekemoer (STSCI), E-CDF-S Team

We report the first results on the angular structure on the Extended Chandra Deep Field-South, which consists of a mosaic of 2x2 ACIS-I fields centered at the original Chandra Deep Field-South. In this poster, we present angular auto-correlation functions ( $w_{\rm
xx}(\theta)$) of the X-ray sources published by our team (Lehmer et al. 2005; ApJS in press) as well as cross-correlation functions ( $w_{\rm
xg}(\theta)$) between the X-ray sources and galaxies in the COMBO-17 photometric redshift catalog (Wolf et al. 2004).

We were able to measure significant angular auto correlation ( $w_{\rm
xx}(\theta)$) down to 10 arcseconds separately for the X-ray sources detected in the 0.5-2.0 keV and 2-8 keV bands.

By further investigating the cross-correlation with galaxies, we can obtain 1) large number of pairs, giving high signal-to-noise ratios, and 2) thick cuts in the photometric redshift in the galaxy catalog. By doing so, we can roughly trace the redshift evolution of the clustering properties (large scale environments of the X-ray AGNs) even before full redshifts on the X-ray sources themselves are available. We have calculated $w_{\rm
xg}(\theta)$ values between the X-ray sources detected in the 0.5-2.0 keV and 2-8 keV bands and galaxies in three thick photometric redshift ranges (0.1$<$0.3, 0.3$<$0.8, and 0.8$<$1.4). Our preliminary results show, in all photometric redshift ranges a positive correlation up to 10-100 arcseconds.

We also plan to report on the implied 3-D clusterings from both auto- and cross-correlations and their redshift dependences.

The X-ray Luminosity Functions of Galaxies Derived from the GOODS

Andrew Ptak (JHU), Bahram Mobasher (STSci), Ann Hornschemeier (GSFC), Colin Norman (JHU)

We present soft X-ray luminosity functions (XLFs) derived from GOODS data, where for the first time XLFs are derived for early and late-type galaxies at z $\sim$ 0.25 and z $\sim$ 0.75. We derived XLFs both before and after selecting only normal/starburst galaxies from the GOODS data. The slopes of the early-type galaxy XLFs tend to be slightly flatter than the late-type galaxy XLFs. We find that the normal/starburst galaxy XLFs are significantly steeper at z$>$0.5 than at z$<$0.5. The XLF shape clearly differs from the Schechter function fits to the J-band luminosity functions, however our early-type galaxy XLFs have a similar overall normalization as the early-type galaxy J-band luminosity function rescaled to the X-ray band, consistent with both being tied to the older stellar population. The late-type XLFs derived from the normal/starburst sample agree well with rescaled local FIR luminosity functions assuming (1+z)$^3$ luminosity evolution, at both high and low redshift. This agreement is also not surprising since both samples should be dominated by star-forming galaxies.

Searching for X-ray Luminous Star-forming Galaxies with Chandra, XMM and 2dFGRS

Panayiotis Tzanavaris, Ioannis Georgantopoulos (National Observatory Athens), Antonis Georgakakis (Imperical College London)

We cross-correlated the Chandra XASSIST and XMM-Newton Serendipitous Source Catalogs with the 2dF Galaxy Redshift Survey database (2dFGRS), looking for galaxies whose X-ray emission is not dominated by an AGN but by stellar processes (``normal'' galaxies). We found 20 2dFGRS galaxies within 3 arcsec of a Chandra source, and 18 galaxies within 6 arcsec of an XMM-Newton source. We used the classification scheme of Ho et al. (1997) to classify six 2dFGRS spectra as H II nuclei, and two spectra as possible H II nuclei. The rest of the objects are absorption line galaxies, emission+absorption galaxies, AGN and LINERs. For all objects we calculated the X-ray luminosity, $L_X$, the logarithimic ratio of X-ray to optical fluxes, log $f_X/f_O$, and the hardness ratio, HR. Some of the ``normal'' galaxies found have log $f_X/f_O > -2$, although log $f_X/f_O < -2$ has often been used to separate ``normal'' galaxies from AGN. However, all ``normal'' galaxies have log $L_X < 42$. The implication of our results for X-ray surveys is that the empirical criterion log $L_X < 42$ is more reliable than log $f_X/f_O < -2$ for separating ``normal'' galaxies from AGN.

[PDF of the poster]

The X-ray Luminosity Function and log N - log S of Normal Galaxies

Panayiotis Tzanavaris, Ioannis Georgantopoulos, Athanasios Akylas (National Observatory Athens), Antonis Georgakakis (Imperial College London), Andreas Zezas (Harvard-Smithsonian Center for Astrophysics)

By combining XMM-Newton and Chandra data (XMM-NHS, 1XMM, CDF-N, CDF-S and Chandra XASSIST/SDSS) we obtained the largest sample to-date ($\sim
200$ objects) of X-ray selected, normal (non-AGN dominated) galaxies. We present the number count distribution, $\log N - \log S$, and the X-ray luminosity function of normal galaxies, separately for early and late-type galaxies.