Chandra's First Decade of Discovery

Session 3: The Cosmic Evolution of AGN

Supermassive Black Hole Growth Over Cosmic Time: X-ray Constraints on the Demographics and Physics of Active Galaxies

William Brandt, Penn State University

Extragalactic X-ray surveys over the past decade have dramatically improved our understanding of how the majority populations of active galactic nuclei (AGNs) evolve over most of the history of the Universe. I will describe some of these exciting results, drawing from the findings of both deep and wide surveys. Topics covered will include (1) the utility and limitations of X-ray surveys for finding distant AGNs; (2) constraints upon the most heavily obscured AGNs in the distant universe; (3) the cosmic evolution of AGN spectral energy distributions and accretion processes; and (4) the AGN content of forming galaxies at high redshifts. I will also discuss some key outstanding problems and prospects for short-term and long-term advances.

[Video of this talk]

The X-ray AGN Fraction and an AGN/Star Formation Sequence from the Chandra Multiwavelength Project

Paul J Green, SAO/CXC
Daryl Haggard (UWa), Anca Constantin (JMU), Tom Aldcroft (SAO), Scott Anderson (UWa), Dong-Woo Kim (SAO), Wayne Barkhouse (UND)

A fundamental constraint to all theories modeling the interplay of supermassive black hole accretion and galaxy evolution should be the the fraction of galaxies in the local universe that host actively accreting nuclei, yet that number is poorly known. X-ray emission is the most reliable primary signature of AGN activity. The Chandra Multiwavelength Project (ChaMP) has carefully analyzed 323 Chandra fields (about 30 square deg) that overlap the SDSS, characterized all optical/X-ray matches, employed SDSS and our own ChaMP spectroscopy as well as photometric redshifts. Our detailed volume completeness maps allow us to report here on the AGN fraction as a function of absolute optical magnitude, X-ray luminosity, and redshift, from a parent sample of thousands of SDSS galaxies. We further report on our confirmation with X-rays of a sequence from starforming to active to passive galaxies that matches trends in both optical host galaxy characteristics and in large scale environment.

[Video of this talk]

AGN as tracers of the Large scale structure: the golden contribution of Chandra

Nico Cappelluti, MPE/UMBC

The discovery with Chandra that the source number counts of AGN were rising in proximity of galaxy clusters opened the doors for the study of the interactions between the super-massive black holes and the large scale environment. After reviewing the first discoveries of the excess source density in high-z galaxy cluster and its evolution, I will show how the study of the clustering of AGN in high density environments has evolved by making use of the recent studies performed with wide field X-ray survey like XMM/Chandra-COSMOS and with archival studies with ROSAT.

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The Chandra COSMOS Survey: Early Results

Martin Elvis, Harvard-Smithsonian Center for Astrophysics
and the Chandra COSMOS Team

The Chandra COSMOS Survey used ACIS-I to cover 0.5 sq.deg. to 160 ksec depth and an additional 0.4 sq.deg to 80 ksec, observed primarily in 2007. The C-COSMOS combination of depth and area produces large numbers of sources, 1761 point and some 200 extended sources. These numbers allow for good statistics on previously sparse samples (e.g. high z quasars), and for the discovery of rare classes of objects (e.g. double AGNs). The depth of C-COSMOS is well matched to the depth of the 40+ complementary imaging bands from radio to UV for the COSMOS field, which enabled >95% identifications rates, SEDs and accurate photo-zs to be found rapidly. All the sources and identifications are now submitted or in press.We present the latest early science results including: (1) z>3 quasars logN-logS, (2) a population of joint starburst/obscured AGN galaxies, (3) AGN vs. Starburst clustering, (4) Weak Lensing masses for AGN dark matter haloes, (5) off-nuclear (ULX?) objects, (6) Double AGNs, including CID-42 which shows high velocity redshifted Fe-K absorption, which we interpret as a “backlit wind.”

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AMUSE-Virgo: the complete nuclear X-ray census

Elena Gallo, MIT
T. Treu, C. Leipski, R. Antonucci (UCSB), J.-H. Woo (UCLA)

We completed the census of nuclear X-ray activity in 100 early type Virgo galaxies observed by Chandra as part of the AMUSE-Virgo survey. The stellar mass distribution of the sample peaks below 10E+10 MSun, in a regime where nuclear super-massive black holes (SMBHs) may be difficult to retain by bulges due to their shallow potential wells, and could even be replaced by massive nuclear star clusters. Out of these 100 objects, 32 show a nuclear X-ray source, 6 of which also host a massive nuclear cluster as visible from high-resolution, archival HST images. As the sensitivity threshold of our Chandra survey is close to the Eddington limit for a solar mass object, low-mass X-ray binaries (LMXBs) within the inner few arcsec are a likely source of contamination to the nuclear X-ray emission. This is assessed by assigning to each X-ray nucleus a weight which corresponds to (1-PX), where PX is the probability of hosting a LMXB of luminosity LX as evaluated from the known shape and normalization of the X-ray luminosity function of LMXBs in globular clusters/the field, respectively in the presence/absence of a nuclear star cluster. We construct the mass-dependent distribution of active SMBHs for these 100 early types, the majority of which are deemed formally `inactive'. We confirm that the fraction fX of active nuclear SMBHs is an increasing function of the host stellar mass. The differential logarithmic X-ray luminosity function of active SMBHs in our sample scales with the X-ray luminosity as LX(0.5+/- 0.1) between 3E+38 and 10E+42 erg/s; the fitted slope is much shallower than for LMXBs, confirming the different nature of the nuclear X-ray sources' population.

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Results from the AEGIS-X survey of the Extended Groth Strip

Elise Laird, Imperial College London
AEGIS-X team

The AEGIS-X survey is a 3.4Ms Chandra survey of the Extended Groth Strip (EGS) region, designed primarily for studying the co-evolution of black holes and their host galaxies. The original phase of the survey comprised of 8 contiguous ACIS-I pointings, each with nominal exposure 200ks, covering a total area of approximately 0.67 deg2 in a strip of length 2 degrees. A total of 1325 band-merged sources were detected to a Poisson probability limit of 4 x 10-6, with limiting fluxes of 5.3 x 10-17 erg cm2 s-1 in the soft (0.5-2 keV) band and 3.8 x 10-16 erg cm-2 s-1 in the hard (2-10 keV) band. These observations cover a region with excellent supporting ground and space-based panchromatic data (e.g. GALEX, HST/ACS, CFHTLS, Spitzer/IRAC, Spitzer/MIPS, VLA) and ~20,000 spectroscopic redshifts from the DEEP2 and DEEP3 surveys. The second phase of AEGIS-X has recently been completed and comprises of an additional 1.6Ms in the central 3 pointings in the strip, where the supporting data is strongest. I will present the first results from the new, deeper AEGIS-X survey as well as reviewing some of the key results from the survey to date. In particular I will focus on the optical spectral properties, environment, stellar mass function and morphology of the X-ray sources.

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