X-ray surveys of the extragalactic universe are now able to detect
significant numbers of AGN out to high redshift (z~5). We highlight some
results from the Chandra Multiwavelength Project (ChaMP) to ...measure the X-ray
luminosity function out to these early epochs. At z > 3, we show that the
comoving space density of luminous (log Lx > 44.5) AGN has a behavior similar
to the optical QSO luminosity function. With a newly compiled sample of AGN
from ChaMP supplemented with those from additional surveys including the
Chandra Deep fields, we present a preliminary measure of the luminosity
function in the hard (2-8 keV) band. With 37 AGN at z > 3, we continue to see a
decline in the space density at high redshift over a wider range in luminosity.
We discuss the need to identify a larger sample of obscured AGN at high
redshift to determine if an early epoch of hidden supermassive black hole
growth occurred.
Astrophys.J. 605 (2004) L105-L108 The Chandra Multiwavelength Project (ChaMP) has discovered a jet-like
structure associated with a newly recognized QSO at redshift z=1.866. The
system was 9.4 arcmin ...off-axis during an observation of 3C 207. Although
significantly distorted by the mirror PSF, we use both a raytrace and a nearby
bright point source to show that the X-ray image must arise from some
combination of point and extended sources, or else from a minimum of three
distinct point sources. We favor the former situation, as three unrelated
sources would have a small probability of occurring by chance in such a close
alignment. We show that interpretation as a jet emitting X-rays via inverse
Compton (IC) scattering on the cosmic microwave background (CMB) is plausible.
This would be a surprising and unique discovery of a radio-quiet QSO with an
X-ray jet, since we have obtained upper limits of 100 microJy on the QSO
emission at 8.46 GHz, and limits of 200 microJy for emission from the putative
jet.
Astrophys.J.618:123-138,2004 We present X-ray and optical analysis of 188 AGN identified from 497 hard
X-ray (f (2.0-8.0 keV) > 2.7x10^-15 erg cm^-2 s^-1) sources in 20 Chandra
fields (1.5 deg^2) ...forming part of the Chandra Multi-wavelength Project. These
medium depth X-ray observations enable us to detect a representative subset of
those sources responsible for the bulk of the 2-8 keV Cosmic X-ray Background.
Brighter than our optical spectroscopic limit, we achieve a reasonable degree
of completeness (77% of X-ray sources with counter-parts r'< 22.5 have been
classified): broad emission line AGN (62%), narrow emission line galaxies
(24%), absorption line galaxies (7%), stars (5%) or clusters (2%). We find that
most X-ray unabsorbed AGN (NH<10^22 cm^-2) have optical properties
characterized by broad emission lines and blue colors, similiar to
optically-selected quasars from the Sloan Digital Sky Survey but with a slighly
broader color distribution. However, we also find a significant population of
redder (g'-i'>1.0) AGN with broad optical emission lines. Most of the X-ray
absorbed AGN (10^22<NH<10^24 cm^-2) are associated with narrow emission line
galaxies, with red optical colors characteristically dominated by luminous,
early type galaxy hosts rather than from dust reddening of an AGN. We also find
a number of atypical AGN; for instance, several luminous AGN show both strong
X-ray absorption (NH>10^22 cm^-2) and broad emission lines. Overall, we find
that 81% of X-ray selected AGN can be easily interpreted in the context of
current AGN unification models. Most of the deviations seem to be due to an
optical contribution from the host galaxies of the low luminosity AGN.
X-ray surveys of the extragalactic universe are now able to detect significant numbers of AGN out to high redshift (z~5). We highlight some results from the Chandra Multiwavelength Project (ChaMP) to ...measure the X-ray luminosity function out to these early epochs. At z > 3, we show that the comoving space density of luminous (log Lx > 44.5) AGN has a behavior similar to the optical QSO luminosity function. With a newly compiled sample of AGN from ChaMP supplemented with those from additional surveys including the Chandra Deep fields, we present a preliminary measure of the luminosity function in the hard (2-8 keV) band. With 37 AGN at z > 3, we continue to see a decline in the space density at high redshift over a wider range in luminosity. We discuss the need to identify a larger sample of obscured AGN at high redshift to determine if an early epoch of hidden supermassive black hole growth occurred.
The Chandra Multiwavelength Project (ChaMP) has discovered a jet-like structure associated with a newly recognized QSO at redshift z=1.866. The system was 9.4 arcmin off-axis during an observation of ...3C 207. Although significantly distorted by the mirror PSF, we use both a raytrace and a nearby bright point source to show that the X-ray image must arise from some combination of point and extended sources, or else from a minimum of three distinct point sources. We favor the former situation, as three unrelated sources would have a small probability of occurring by chance in such a close alignment. We show that interpretation as a jet emitting X-rays via inverse Compton (IC) scattering on the cosmic microwave background (CMB) is plausible. This would be a surprising and unique discovery of a radio-quiet QSO with an X-ray jet, since we have obtained upper limits of 100 microJy on the QSO emission at 8.46 GHz, and limits of 200 microJy for emission from the putative jet.
We present X-ray and optical analysis of 188 AGN identified from 497 hard X-ray (f (2.0-8.0 keV) > 2.7x10^-15 erg cm^-2 s^-1) sources in 20 Chandra fields (1.5 deg^2) forming part of the Chandra ...Multi-wavelength Project. These medium depth X-ray observations enable us to detect a representative subset of those sources responsible for the bulk of the 2-8 keV Cosmic X-ray Background. Brighter than our optical spectroscopic limit, we achieve a reasonable degree of completeness (77% of X-ray sources with counter-parts r'< 22.5 have been classified): broad emission line AGN (62%), narrow emission line galaxies (24%), absorption line galaxies (7%), stars (5%) or clusters (2%). We find that most X-ray unabsorbed AGN (NH<10^22 cm^-2) have optical properties characterized by broad emission lines and blue colors, similiar to optically-selected quasars from the Sloan Digital Sky Survey but with a slighly broader color distribution. However, we also find a significant population of redder (g'-i'>1.0) AGN with broad optical emission lines. Most of the X-ray absorbed AGN (10^22<NH<10^24 cm^-2) are associated with narrow emission line galaxies, with red optical colors characteristically dominated by luminous, early type galaxy hosts rather than from dust reddening of an AGN. We also find a number of atypical AGN; for instance, several luminous AGN show both strong X-ray absorption (NH>10^22 cm^-2) and broad emission lines. Overall, we find that 81% of X-ray selected AGN can be easily interpreted in the context of current AGN unification models. Most of the deviations seem to be due to an optical contribution from the host galaxies of the low luminosity AGN.
The DDO IVC Distance Project Gladders, Michael D; Clarke, Tracy E; Burns, Christopher R ...
arXiv (Cornell University),
11/1998
Journal Article
Open access
We present the first set of distance limits from the David Dunlap Observatory
Intermediate Velocity Cloud (DDO IVC) distance project. Such distance measures
are crucial to understanding the origins ...and dynamics of IVCs, as the distances
set most of the basic physical parameters for the clouds. Currently there are
very few IVCs with reliably known distances. This paper describes in some
detail the basic techniques used to measure distances, with particular emphasis
on the the analysis of interstellar absorption line data, which forms the basis
of our distance determinations. As an example, we provide a detailed
description of our distance determination for the Draco Cloud. Preliminary
distance limits for a total of eleven clouds are provided.
The DDO IVC Distance Project Gladders, Michael D; Clarke, Tracy E; Burns, Christopher R ...
arXiv.org,
11/1998
Paper
Open access
We present the first set of distance limits from the David Dunlap Observatory Intermediate Velocity Cloud (DDO IVC) distance project. Such distance measures are crucial to understanding the origins ...and dynamics of IVCs, as the distances set most of the basic physical parameters for the clouds. Currently there are very few IVCs with reliably known distances. This paper describes in some detail the basic techniques used to measure distances, with particular emphasis on the the analysis of interstellar absorption line data, which forms the basis of our distance determinations. As an example, we provide a detailed description of our distance determination for the Draco Cloud. Preliminary distance limits for a total of eleven clouds are provided.
