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Journal ArticleDOI

Spectral energy distributions and multiwavelength selection of type 1 quasars

TL;DR: In this article, the spectral energy distributions (SEDs) of 259 quasars with both Sloan Digital Sky Survey (SDS) and Spitzer photometry were analyzed.
Abstract: We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z ~ 3, with predictions to z = 7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as 50% for individual quasars when inferring a bolometric luminosity from an optical luminosity. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio.

Summary (2 min read)

3. MIR/OPTICAL COLORS OF TYPE 1 QUASARS

  • For the Spitzer color, the authors chose the two highest S/N bands (S3:6 and S4:5); this choice happens to produce the greatest separation of classes and has the added attraction that it does not rely on the longer wavelength bands that will be lost when Spitzer’s coolant runs out.
  • Judicious rotation of the axes in Figure 6 may allow for relatively clean AGN selection without having to rely on morphology information.
  • Quasars with z > 2:2 have redder optical colors even if they are not dust-reddened, and a large fraction of this population will still be identified by the SDSS quasar-selection algorithm.
  • A multidimensional MIR + optical Bayesian color-selection approach (Richards et al. 2004) that avoids any morphology bias may yield optimal completeness and efficiency for all AGN subclasses and will be the subject of future work.

4. THE OBSCURED QUASAR FRACTION

  • SinceMIR emission fromAGNs comes from larger scales and is thought to bemore isotropic than optical/UVemission, theMIR is an ideal part of the spectrum to constrain the fraction of quasars that are obscured (within the context of the so-called unifiedmodel; Antonucci 1993).
  • E.g., Polletta et al. 2000; Kuraszkiewicz et al. 2003; Risaliti & Elvis 2004), complete SEDs have been compiled for only a small number (P100) of quasars and the mean SED from Elvis et al. (1994) is arguably still the best description of the SED of quasars and is certainly the most commonly used.
  • To assess the importance of the host galaxy correction where it matters most, the authors determine the ratio of host galaxy to total luminosity at 1.6 m in the rest frame, where the elliptical template spectrum has its peak.
  • The standard deviation of the overall mean and the luminosity- and color-subdivided mean SEDs give the reader an idea of the range of SED shapes.
  • There are significant differences between the most and least optically luminous quasars in their sample.

6. BOLOMETRIC LUMINOSITIES AND ACCRETION RATES

  • The determinations of quasar physical parameters such as bolometric luminosity, black hole mass, and accretion rate have been revolutionized by two bodies of work from the past decade or so.
  • As discussed above, the biases inherent to the sample of objects used by Elvis et al. (1994) in addition to these authors’ warnings of the diversity of individual SEDs, coupled with the use of their mean SED as a single universal template, is what motivates this investigation.
  • It seems likely that the minimum in this region results from this region being a relative minimum in the combination of host galaxy contamination in the near-IR and dust extinction in the UV.
  • Figures 12 and 13 demonstrate that the smallest bolometric corrections and errors are found at optical wavelengths.
  • Clearly, if the authors are ever to understand the accretion rate distribution of quasars, they must either measure the bolometric luminosity directly or determine bolometric corrections to an accuracy better than that which is afforded by assuming the mean SED.

7. CONCLUSIONS

  • The authors have compiled a sample of 259 SDSS type 1 quasars with four-band Spitzer IRAC detections.
  • Figure 14 presents the individual SEDs of each of the 259 quasars in their sample.
  • The SDSS spectra are shown as solid black lines (smoothed by a 19 pixel boxcar).

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SPECTRAL ENERGY DISTRIBUTIONS AND MULTIWAVELENGTH SELECTION OF TYPE 1 QUASARS
Gordon T. Richards,
1,2
Mark Lacy,
3
Lisa J. Storrie-Lombardi,
3
Patrick B. Hall,
4
S. C. Gallagher,
5
Dean C. Hines,
6
Xiaohui Fan,
7
Casey Papovich,
7
Daniel E. Vanden Berk,
8
George B. Trammell,
8
Donald P. Schneider,
8
Marianne Vestergaard,
7
Donald G. York,
9,10
Sebastian Jester,
11, 12
Scott F. Anderson,
13
Tama
´
sBudava
´
ri,
2
and Alexander S. Szalay
2
Received 2006 January 24; accepted 2006 May 26
ABSTRACT
We present an analysis of the mid-infrared ( MIR) and optical properties of type 1 (broad-line) quasars detected by
the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z 3, with predictions to z ¼ 7. We
demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei
(AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259
quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and
ROSAT data, where available. We discuss how the spectral diversity of quasars influences the determination of bolo-
metric luminosities and accretion rates; assuming the mean SED can lead to errors as large as 50% for individual quasars
when inferring a bolometric luminosity from an optical luminosity. Finally, we show that careful consideration of the
shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened / obscured
AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio.
Subject h eadinggs: catalogs galaxies: active infrared: galaxies quasars: general radio continuum: galaxies
surveys ultraviolet: galaxies X-rays: galaxies
Online material: machine-readable tables
1. INTROD UCTION
Access to the mid-infrared ( MIR) region opens up new realms
for quasar science as we are able to study large numbers of ob-
jects with high signal-to-noise ratio data in this bolometrically
important band for the first time. At least four distinct energy gen-
eration mechanisms are at work in active galactic nuclei (AGNs)
from jets in the radio, dust in the IR, accretion disks in the optical
UVsoftX-ray, and Compton upscattering in hot coronae in the
hard X-ray. All of these spectral regions need to be sampled with
high precision if we are to understand the physical processes
governing AGN emission. The Spitzer Space Telescope (Werner
et al. 2004) allows the first robust glimpse of the physics of the
putative dusty torus in AGNs out to z 23 and makes it pos-
sible to compare high-quality mid-IR data to the expectations of
the latest models (e.g., Nenkova et al. 2002; Dullemond & van
Bemmel 2005; Fritz et al. 2006).
MIR photometry from Spitzer has provided a better census of
active nuclei in galaxies than has been previously possible (e.g.,
Lacy et al. 2004). Optical surveys are biased against heavily
reddened and obscured objects, and even X-ray surveys may fail
to uncover Compton-thick sources (e.g., Treister et al. 2006).
Thus, the MIR presents an attractive window for determining the
black hole accretion history of the universe. To that end, Spitzer
will be of considerable utility in helping to decipher the nature of
the M
BH
- relation (e.g., Tremaine et al. 2002), in terms of mak-
ing a complete census of AGNs—a necessary condition for a full
understanding of the physical relationship between black holes
and their host galaxies.
High-sensitivity, high-accuracy MIR photometry also fills a
huge gap in our knowledge of the overall spectral energy dis-
tribution (SED) of AGNs, which now lacks only detailed far-IR/
centimeter and extreme-UV meas urements for a large sample of
quasars. Without the mid-IR data, we have been forced to rely on
the mean properties of a few dozen of the brightest quasars (e.g.,
Elvis et al. 1994) to estimate bolometric luminosities (and, in turn,
Eddington masses and accretion rates) for quasars. Since the 1
100 m part of the spectrum contributes nearly 40% of the bolo-
metric luminosity, this added knowledge represents a significant
gain in our ability to explore the properties of AGNs as a function
of the bolometric luminosity.
This paper builds on and extends the results from recent pa-
pers describing the Spitzer MIR color distribution of AGNs.
Lacy et al. (2004) showed that MIR colors alone can be used to
select AGNs with both high efficiency and completeness, includ-
ing both dust-reddened and optically obscured (type 2) AGNs
that may otherwise be overlooked by optical selection techniques.
We will show that the addition of optical colors and morphology
can be used to improve the MIR-only selection efficiency of type 1
quasars (including those that are moderately reddened).
A
1
Princeton University Observatory, Peyton Hall, Princeton, NJ 08544.
2
Department of Physics and Astronomy, The Johns Hopkins University,
3400 North Charles Street, Baltimore, MD 21218-2686.
3
Spitzer Science Center, California Institute of Technology, Mail Code 220-6,
Pasadena, CA 91125.
4
Department of Physics and Astronomy, York University, 4700 Keele Street,
Toronto, ON M3J 1P3, Canada.
5
Department of Physics and Astronomy, UCLA, Mail Code 154705, 475
Portola Plaza, Los Angeles, CA 90095.
6
Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301.
7
Steward Observatory, University of Arizona, 933 North Cherry Avenue,
Tucson, AZ 85721.
8
Department of Astronomy and Astrophysics, Pennsylvania State Univer-
sity, 525 Davey Laboratory, University Park, PA 16802.
9
Department of Astronomy and Astrophysics, University of Chicago, 5640
South Ellis Avenue, Chicago, IL 60637.
10
Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue,
Chicago, IL 60637.
11
Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510.
12
School of Physics and Astronomy, Southampton University, Southampton
SO17 1BJ, UK.
13
Department of Astronomy, University of Washington, Box 351580, Seattle,
WA 9 8 1 9 5.
470
The Astrophysical Journal Supplement Series, 166:470497, 2006 October
# 2006. The American Astronomical Society. All rights reserved. Printed in U.S.A.

Stern et al. (2005) also describe a MIR selection technique for
AGNs, making statistical arguments that the obscured AGN frac-
tion may be as high as 76%. We reconsider their argument in light
of the influence that the shape of the mean quasar spectral energy
distribution (SED) has on determining the obscured quasar frac-
tion. Such considerations allow us to demonstrate that the true ob-
scured AGN fraction must be lower than that determined by Stern
et al. (2005).
Finally, Hatziminaoglou et al. (2005) investigated the combined
optical + MIR color distribution of quasars by combining data
from the ELAIS-N1 field in the Spitzer Wide-Area Infrared Extra-
galactic Survey (SWIRE; Lonsdale et al. 2003) with data from the
Sloan Digital Sky Survey (SDSS; York et al. 2000). Using the data
from 35 SDSS quasars they determine the mean optical-MIR SED
of type 1 quasars and investigate their mass and bolometric lumi-
nosity distribution. We expand on these results by determining a
number of different ‘mean’ SEDs as a function of color and lumi-
nosity for 259 SDSS quasars in the Spitzer Extragalactic First Look
Survey
14
(XFLS), SWIRE
15
ELAIS-N1/N2, and SWIRE Lockman
Hole areas. We use these SEDs to demonstrate that the diversity of
quasar SEDs must be considered when determining bolometric
luminosities and accretion rates for individual quasarsas was
emphasized in the seminal SED work of Elvis et al. (1994).
Section 2 reviews the data sets used in our analysis. In x 3we
explore the MIR color-redshift relation and MIR-optical color-
color space occupied by type 1 quasar s. In addition to showing
these relations for the data, we also show the predicted relations
derived from two quasar SEDs convolved with the SDSS and
Spitzer filters curves : one SED derived largely from broadband
photometry ( Elvis et al. 1994), the other from a mean optical +
IR spectral template (Glikman et al. 2006). Section 4 presents a
brief discussion of the determination of the type 1 to type 2 ratio
of quasars. In x 5 we discuss the radio through X-ray SED of qua-
sars and construct new MIR-optical templates from our sample.
We present an overall mean SED along with mean SEDs for sub-
sets of optically luminous/dim, MIR luminous/dim, and optically
blue/red quasars in order to explor e how different optical/MIR
properties are related to the overall SED. Section 6 discusses the
implications of our new SED templates on the determination of
bolometric luminosities and accretion rates. Our conclusions are
presented in x 7.
Throughout this paper we will distinguish between normal
type 1 quasars, dust-reddened/extincted type 1 quasars, and type 2
quasars. By ‘type 1 quasars,’ we mean those quasars having broad
lines and optical colors/ spectral indices that are roughly consistent
with a Gaussian spectral index distribution of
¼0:5 0:3
( f
/
). Red dened type 1 quasars are those quas ars that have
broad lines but have spectral indices that are redder than about
¼1 (e.g., Gregg et al. 2002). Optical surveys can find such
quasars up to E(B V ) 0:5butareincreasinglyincomplete
above E(B V ) 0:1 (Richards et al. 2003). By type 2 quasars,
we mean those that lack rest-frame optical/UV broad emission
lines and have nuclei that are completely obscured in the optical
such that the optical colors are consistent with the host galaxy.
Throughout this paper we use a CDM cosmology with H
0
¼
70 km s
1
Mpc
1
,
¼ 0:7, and
m
¼ 0:3, consistent with the
WMAP cosmology (Spergel et al. 2003, 2006).
2. THE DATA
We investigate the mid-IR and optical properties of type 1
quasars that are detected in both the SDSS and in all four bands
of the Spitzer Infrared Array Camera ( IRAC; Fazio et al. 2004).
The Spitzer data are taken from the XFLS and SWIRE ELAIS-N1,
ELAIS-N2, and Lockman Hole areas, which have (R.A., decl.)
centers of (259N5, 59N5), (242N75, 55N0), (249N2, 41N029), and
(161N25, 58N0), respectively.
We begin with SDSS-DR3 type 1 quasars cataloged by
Schneider et al. (2005), the majority of which were selected by
the algorithm given by Richards et al. (2002). This catalog in-
cludes matches to the FIRST (Becker et al. 1995) survey with the
VLA, ROSAT ( Voges et al. 2000), and 2MASS (Skrutskie et al.
1997). For a definition of the SDSS photometric system, see
Fukugita et al. (1996); Adelman-McCarthy et al. (2006) provide
a description of the latest SDSS data release (DR4). All SDSS
magnitudes have been corrected for Galactic extinction accord-
ing to Schlegel et al. (1998).
The 46,420 SDSS quasars of Schneider et al. (2005) are
matched to IRAC detections in the XFLS (main
_
4band.cat;
Lacy et al. 2005b) and the SWIRE ELAIS-N1, -N2, and Lockman
Hole (SWIRE2
_
N1
_
cat
_
IRAC24
_
16jun05.tbl, SWIRE2
_
N2
_
cat
_
IRAC24
_
16jun05.tb l, SWIRE2
_
Lockman
_
cat
_
IRAC24
_
10Nov05.tbl; Surace et al. 2005) areas of sky. The IRAC band-
passes are generally referred to as channels 1 through 4 or as the
3.6, 4.5, 5.8 , and 8.0 m bands, respectively. For a quasar spec-
trum with MIR spectral index of
¼1(f
/
), the effec-
tive wavelengths of the IRAC bandpasses are actually closer to
3.52, 4.46, 5.67, and 7.70 m. The SWIRE catalogs also include
24 m photometry from the Multiband Imaging Photometer for
Spitzer (MIPS; Rieke et al. 2004). In the XFLS field, 24 m
sources are cataloged by Fadda et al. (2006) and we include
matches from that catalog as well. As the limits of the mid-IR
catalogs are much deeper than the SDSS spectroscopic survey,
we consider only objects detected in all four IRAC bands. Within
a matching radius of 1B0 there are 44 SDSS-DR3 quasar matches
in the XFLS area, 29 in the ELAIS-N1 area, 44 in the ELAIS-N2
area, and 142 in the Lockman Hole area. All but one of the op-
tically selected SDSS quasars has four-band IRAC coverage in
the regions of overlap between the SDSS and Spitzer data; see
Figures 1 and 2. The ex ception is SDSS J104413.47 +580858. 9
(z ¼ 3:7), which has only a limit in IRAC channel 3.
To construct the most detailed quasar spectral energy distribu-
tions (SEDs) possible, we include data available at other wave-
lengths. We include matches to MIPS 70 m sources in the XFLS
(FLS70
_
sn7
_
jul05.txt; Frayer et al. 2006) and in the SWIRE
(SWIRE2
_
EN1
_
70um_23nov05.tbl, SWIRE2
_
EN2
_
70um
_
23nov05.tbl, SWIRE3
_
Lockman
_
70um
_
23nov05.tbl; Surace
et al. 2005) areas. No MIPS 160 m data are included as the
flux density limits of these data in the XFLS and SWIRE areas
are much brighter than expected flux densities of even the bright-
est SDSS-DR3 quasars in these fields. For the SDSS quasars in
the ELAIS fields we have extracted 15 mphotometryfromthe
Rowan-Robinson et al. (2004) catalog. We also extract J /H/K and
radio information from this catalog if that information was not
otherwise available.
Some of these areas of sky have been observed by GALEX
(Martin et al. 2005), and the data were released as part of GALEX
GR1. Quasars are readily detected by GALEX (see Bianchi et al.
2005 and Seibert et al. 2005); thus, we also include GALE X pho-
tometry where available. Matc hing of the GALEX catalogs and
the SDSS DR3 quasar sample is described by Trammell et al.
(2005). The effective wavelengths of the GALEX NUV and
FUV bandpasses (hereafter referred to as n and f magnitudes)
are 2267 and 1516 8. GALEX photometry has been corrected
for Galactic extinction assuming A
n
/E(B V ) ¼ 8:741 and
A
f
/E(B V ) ¼ 8:376 (Wyder et al. 2005). A total of 55 and 88
14
See http://ssc.spitzer.ca ltech.edu/fls/.
15
See http://swire.ipac.caltech.edu/swire/.
SEDs OF TYPE 1 QUASARS 471

of the DR3 quasars have GALEX detections in the f and n bands,
respectively.
In the radio, we have matched to the deeper VLA data taken in
the XFLS area by Condon et al. (2003), which catalogs 5 de-
tections with fluxes higher than 115 Jy (about an order of mag-
nitude deeper than FIRST). Deep VLA data also exists for the
ELAIS and Lockman Hole areas, but only over a small area of
sky (e.g., Ciliegi et al. 1999, 2003).
Most of our objects are fainter than the 2MASS (Skrutskie
et al. 1997) limits, but we have supplemental near-IR data for a
few. Near-IR (JHK
s
) magnitudes for SDSS J1716+5902 were ob-
tained on 2003 September 9 UT using the GRIM II instrument on
the Apache Point Observatory 3.5 m telescope. Dithered images
were obtained and reduced in the standard fashion, using running
flat-fielding and sky-subtraction (e.g., Hall et al. 1998) with all
available good images in a given filter for each object. Four
other sources (SDSS J171732.94+59474 7.5, SDSS J171736.90+
593011.4, SDSS J171748.43+594820.6, and SDSS J171831.73+
595309.4) were observed at Palomar Observatory.
Finally, to better characterize the optical + MIR color distri-
bution of type 1 quasars, we include 87 broadline quasars that are
fainter than the SDSS spectroscopic magnitude limit, but that
Fig. 2.—Location of SDSS-DR3 quasars in the SWIRE ELAIS N1 (left)andN2(right) fields. Red points indicate four-band IRAC sources. Blue points indicate
MIPS 70 m sources. Open triangles indicate SDSS-DR3 quasars. Green circles indicate SDSS-DR3 quasars with IRAC detections in all four bands.
Fig. 1.—Location of SDSS-DR3 quasars in the XFLS (left) and SWIRE Lockman Hole (right) fields. Red, yellow, and blue points represent IRAC, IRAC
verification, and MIPS70 sources, respectively. Open triangles represen t SDSS-DR3 quasars. Green circles represent SDSS-DR3 quasars with IRAC detections in all
four bands. Open pentagons indicate GALEX-detected SDSS quasars.
RICHARDS ET AL.472 Vol. 166

TABLE 1
SDSS-Spitzer Quasar Photometry I
Name (SDSS J) z
em
L
bol
a
log (ergs s
1
)
L
opt
b
log (ergs s
1
)
L
ir
c
log (ergs s
1
)BC
a
X-Ray
log (counts s
1
)
f
(AB mag)
n
(AB mag)
u
(AB mag)
g
(AB mag)
r
(AB mag)
i
(AB mag)
z
(AB mag)
105705.39+580437.4 .......... 0.140 45.06 44.49 44.78 10.60 0.708 18.31 0.08 18.15 0.04 17.92 0.03 17.61 0.05 17.25 0.02 16.83 0.02 16.56 0.04
171902.28+593715.9 .......... 0.178 45.21 44.74 44.93 9.41 1.221 18.10 0.01 17.99 0.01 17.49 0.02 17.50 0.02 17.36 0.02 17.06 0.02 17.20 0.02
160655.34+534016.8 .......... 0.214 45.13 44.45 44.91 11.87 ... ... ... 18.85 0.03 18.71 0.02 18.22 0.02 17.86 0.02 17.91 0.03
163111.28+404805.2........... 0.258 45.68 45.27 45.19 9.84 0.551 ... ... 16.98 0.01 17.05 0.02 17.08 0.01 17.10 0.01 16.86 0.01
171207.44+584754.4 .......... 0.269 45.49 45.06 45.12 12.29 1.235 17.97 0.01 18.08 0.01 17.83 0.02 17.93 0.02 17.88 0.02 17.94 0.02 17.51 0.02
171033.21+584456.8 .......... 0.281 45.15 44.46 44.95 10.44 ... 20.59 0.04 20.06 0.02 19.58 0.03 19.25 0.03 18.70 0.02 18.52 0.02 18.10 0.03
105644.52+572233.4 .......... 0.286 45.08 44.53 44.78 10.12 ... ... ... 19.36 0.03 19.26 0.02 18.88 0.02 18.69 0.02 18.32 0.02
104739.49+563507.2 .......... 0.303 45.19 44.66 44.88 9.82 ... ... ... 19.16 0.04 19.02 0.04 18.72 0.04 18.57 0.03 18.20 0.03
155936.13+544203.8 .......... 0.308 45.42 44.87 45.15 11.75 ... ... ... 18.55 0.03 18.42 0.04 18.27 0.02 18.38 0.03 17.87 0.03
105626.96+580843.1 .......... 0.342 45.29 44.66 45.03 8.40 ... ... 21.50 0.20 19.45 0.03 18.95 0.02 18.57 0.03 18.46 0.02 17.88 0.02
Note.—Table 1 is available in its entirety in the electronic edition of the Astrophysical Journal Supplement. A portion is shown her e for guidance regarding its form and content.
a
Bolometric (100 m to 10 keV) luminosity and bolometric correction (from 5100 8).
b
1–0.1 m integrated luminosity.
c
1001 m integrated luminosity.

TABLE 2
SDSS-Spitzer Quasar Photometry II
Name (SDSS J) J (Vega) H (Vega) K (Vega)
S
3:6
(Jy)
S
4:5
(Jy)
S
5:8
(Jy)
S
8:0
(Jy)
S
15
(mJy)
S
24
(mJy)
S
70
(mJy)
Radio
(mJy)
L
rad
log (ergs s
1
Hz
1
)
105705.39+580437.4 ........... 14.99 0.08 14.21 0.09 13.48 0.07 2351.5 5.6 2366.9 7.3 2838.0 15.1 6273.4 16.1 ... 16.61 0.02 98.0 0.6 ... <29.69
171902.28+593715.9 ........... 15.89 0.09 15.02 0.09 14.15 0.06 2925.1 293.1 4095.1 409.8 5365.6 541.1 7193.8 720.4 ... 26.91 0.04 22.9 4.0 0.23 29.28
160655.34+534016.8 ........... 16.37 0.10 15.33 0.11 14.32 0.07 1396.7 4.6 1657.2 5.7 2047.6 14.1 2973.1 10.9 7.72 14.80 0.02 37.7 1.6 ... <30.09
163111.28+404805.2............ 16.24 0.10 15.45 0.12 14.48 0.09 2729.7 5.0 3632.2 6.6 4686.4 15.1 6218.9 11.9 ... 16.90 0.03 ... ... <30.26
171207.44+584754.4 ........... 16.26 0.10 15.36 0.09 14.61 0.10 2024.6 203.1 2411.9 242.2 3162.9 321.5 4353.7 437.9 ... 13.34 0.07 ... 0.14 29.45
171033.21+584456.8 ........... 16.90 0.18 15.68 0.11 14.96 0.10 589.2 59.9 708.4 71.8 709.8 78.1 1571.6 159.5 ... 6.06 0.07 44.0 8.0 ... <30.34
105644.52+572233.4 ........... 16.71 0.10 16.33 0.27 15.10 0.12 1161.4 4.4 1280.1 5.2 1417.1 13.2 1742.5 9.7 ... 3.18 0.02 ... ... <30.36
104739.49+563507.2 ........... 16.63 0.16 16.24 0.24 15.51 0.18 572.2 2.6 671.2 2.6 886.3 10.7 1566.3 6.5 ... 8.61 0.02 ... ... <30.41
155936.13+544203.8 ........... 16.61 0.20 16.77 0.10 14.92 0.16 1093.4 2.6 1437.4 3.8 1997.8 8.6 3268.1 8.7 ... 14.59 0.02 ... 3.40 30.96
105626.96+580843.1 ........... 16.74 0.17 16.25 0.27 15.42 0.16 1362.5 5.2 1660.5 4.9 1975.0 15.5 2303.3 9.0 ... 4.23 0.02 ... ... <30.53
Note.—Table 2 is available in its entirety in the electronic edition of the Astrophysical Journal Supplement. A portion is shown her e for guidance regarding its form and content.

Citations
More filters
Journal ArticleDOI
TL;DR: In this article, a novel approach was proposed to distinguish between colour-selected quasars in the redshift range of 0.2 < z < 2.4 by constructing redshift-sensitive g* − i* colour cuts.
Abstract: A minority of the optically selected quasar population are red at optical wavelengths due to the presence of dust along the line of sight. A key focus of many red quasar studies is to understand their relationship with the overall quasar population: are they blue quasars observed at a (slight) inclination angle or do they represent a transitional phase in the evolution of quasars? Identifying fundamental differences between red and blue quasars is key to discriminate between these two paradigms. To robustly explore this, we have uniformly selected quasars from the Sloan Digital Sky Survey with mid-infrared counterparts, carefully controlling for luminosity and redshift effects. We take a novel approach to distinguish between colour-selected quasars in the redshift range of 0.2 < z < 2.4 by constructing redshift-sensitive g* − i* colour cuts. From cross-matching this sample to the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey, we have found a factor ≈ 3 larger fraction of radio-detected red quasars with respect to that of blue quasars. Through a visual inspection of the FIRST images and an assessment of the radio luminosities (rest-frame L 1.4GHz L1.4GHz and L 1.4GHz / L 6μm L1.4GHz/L6μm ⁠), we find that the radio-detection excess for red quasars is primarily due to compact and radio-faint systems (around the radio-quiet – radio-loud threshold). We show that our results rule out orientation as the origin for the differences between red and blue quasars and argue that they provide broad agreement with an evolutionary model.

38 citations

Journal ArticleDOI
TL;DR: In this article, the spectral signatures of active galactic nuclei (AGN) are reviewed, ranging from radio to hard X-ray wavelengths, and the most commonly used methods to find these sources, including optical/UV, radio, infrared, and Xray emission, and optical emission lines.
Abstract: Significant progress has been made in the last few years on understanding how supermassive black holes form and grow. In this paper, we begin by reviewing the spectral signatures of active galactic nuclei (AGN) ranging from radio to hard X-ray wavelengths. We then describe the most commonly used methods to find these sources, including optical/UV, radio, infrared, and X-ray emission, and optical emission lines. We then describe the main observational properties of the obscured and unobscured AGN population. Finally, we summarize the cosmic history of black hole accretion, that is, when in the history of the universe supermassive black holes were getting most of their mass. We finish with a summary of open questions and a description of planned and future observatories that are going to help answer them.

38 citations

Journal ArticleDOI
TL;DR: Powderday as discussed by the authors is a flexible, fast, open-source dust radiative transfer package designed to interface with galaxy formation simulations, which is based on FSPS population synthesis models.
Abstract: We present Powderday, a flexible, fast, open-source dust radiative transfer package designed to interface with galaxy formation simulations Powderday builds on FSPS population synthesis models, Hyperion dust radiative transfer, and employs yt to interface between different software packages We include our stellar population synthesis modeling on the fly, which allows for significant run-time flexibility in the assumed stellar physics We include a model for nebular line emission that can employ either precomputed Cloudy lookup tables (for efficiency), or direct photoionization calculations for all young stars (for flexibility) The dust content follows either observationally-motivated prescriptions, direct modeling from galaxy formation simulations, or a novel approach that includes the dust content via learning-based algorithms from the SIMBA cosmological galaxy formation simulation AGN can additionally be included via a range of prescriptions The output of these models are broadband SEDs, as well as filter-convolved images Powderday is designed to eliminate last-mile efforts by researchers that employ different hydrodynamic galaxy formation models, and seamlessly interfaces with GIZMO, AREPO, GASOLINE, CHANGA, and ENZO We demonstrate the capabilities of the code via three applications: a model for the star formation rate (SFR) - infrared luminosity relation in galaxies (including the impact of AGN); the impact of circumstellar dust around AGB stars on the mid-infrared emission from galaxy SEDs; and the impact of galaxy inclination angle on dust attenuation laws

37 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented a sample of 46 galaxy nuclei from 12 nearby (z < 4500 km s−1) Hickson Compact Groups (HCGs) with a complete suite of 1-24 μm 2MASS + Spitzer nuclear photometry.
Abstract: We present a sample of 46 galaxy nuclei from 12 nearby (z < 4500 km s−1) Hickson Compact Groups (HCGs) with a complete suite of 1-24 μm 2MASS + Spitzer nuclear photometry. For all objects in the sample, blue emission from stellar photospheres dominates in the near-infrared through the 3.6 μm IRAC band. Of 46 galaxy nuclei, 25 (54%) show red mid-infrared continua characteristic of hot dust powered by ongoing star formation and/or accretion onto a central black hole. We introduce αIRAC, the spectral index of a power-law fit to the 4.5-8.0 μm IRAC data, and demonstrate that it cleanly separates the mid-infrared-active and nonactive HCG nuclei. This parameter is more powerful for identifying low-to moderate-luminosity mid-infrared activity than other measures, which include data at rest-frame λ < 3.6 μm that may be dominated by stellar photospheric emission. While the HCG galaxies clearly have a bimodal distribution in this parameter space, a comparison sample from the Spitzer Nearby Galaxy Survey (SINGS) matched in J-band total galaxy luminosity is continuously distributed. A second diagnostic, the fraction of 24 μm emission in excess of that expected from quiescent galaxies, f24D, reveals an additional three nuclei to be active at 24 μm. Comparing these two mid-infrared diagnostics of nuclear activity to optical spectroscopic identifications from the literature reveals some discrepancies, and we discuss the challenges of distinguishing the source of ionizing radiation in these and other lower luminosity systems. We find a significant correlation between the fraction of mid-infrared-active galaxies and the total H I mass in a group and investigate possible interpretations of these results in light of galaxy evolution in the highly interactive system of a compact group environment.

37 citations


Cites background from "Spectral energy distributions and m..."

  • ...Also overplotted is the total galaxy photometry and three SED templates, that of an elliptical galaxy (Silva et al. 1998), a Type 1 (i.e., broad emission-line) AGN (Richards et al. 2006), and the local starburst galaxy M82 (Silva et al. 1998)....

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Journal ArticleDOI
TL;DR: In this article, a low-metallicity galaxy template with a standard AGN template was used to separate the contributions from the host galaxy and the AGN even in the case of limited data points, given that this model has only two free parameters.
Abstract: The infrared spectral energy distributions (SEDs) of $z\gtrsim 5$ quasars can be reproduced by combining a low-metallicity galaxy template with a standard AGN template. The host galaxy is represented by Haro 11, a compact, moderately low metallicity, star-bursting galaxy that shares typical features of high-$z$ galaxies. For the vast majority of $z\gtrsim 5$ quasars, the AGN contribution is well modeled by a standard empirical template with the contamination of star formation in the infrared subtracted. Together, these two templates can separate the contributions from the host galaxy and the AGN even in the case of limited data points, given that this model has only two free parameters. Using this method, we re-analyze 69 $z\gtrsim 5$ quasars with extensive Herschel observations, and derive their AGN luminosities $L_{\rm AGN}$ in a range $\sim (0.78-27.4) \times10^{13}\, L_{\odot}$, the infrared luminosities from star formation $L_{\rm SF,IR} \sim (<1.5-25.7)\times10^{12}\, L_{\odot}$, and the corresponding star formation rates ${\rm SFR}\sim (<290-2650)\, M_\odot/{\rm yr}$. The average infrared luminosity from star formation and the average total AGN luminosity of the $z\gtrsim5$ quasar sample follows the correlation defined by quasars at $z < 2.6$. We assume these quasar host galaxies maintain a constant average SFR ($\sim620\, M_\odot/{\rm yr}$) during their mass assembly and estimate the stellar mass that could form till $z\sim5-6$ to be $\langle M_* \rangle \sim(3-5)\times10^{11} M_\odot$. Combining with the black hole (BH) mass measurements, this stellar mass is adequate to establish a BH-galaxy mass ratio $M_{\rm BH}/M_{*}$ at 0.1-1%, consistent with the local relation.

37 citations

References
More filters
Journal ArticleDOI
TL;DR: In this article, a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed, is presented.
Abstract: We present a full-sky 100 μm map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 μm data, we have constructed a map of the dust temperature so that the 100 μm map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of H2 in molecular clouds. In contrast, high-velocity H I clouds are deficient in dust emission, as expected. To generate the full-sky dust maps, we must first remove zodiacal light contamination, as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 μm DIRBE map against the Leiden-Dwingeloo map of H I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 μm flux. This procedure removes virtually all traces of the zodiacal foreground. For the 100 μm map no significant CIB is detected. At longer wavelengths, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 ± 13 nW m-2 sr-1 at 140 μm and of 17 ± 4 nW m-2 sr-1 at 240 μm (95% confidence). This integrated flux ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. To calibrate our maps, we assume a standard reddening law and use the colors of elliptical galaxies to measure the reddening per unit flux density of 100 μm emission. We find consistent calibration using the B-R color distribution of a sample of the 106 brightest cluster ellipticals, as well as a sample of 384 ellipticals with B-V and Mg line strength measurements. For the latter sample, we use the correlation of intrinsic B-V versus Mg2 index to tighten the power of the test greatly. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening. The maps are expected to be significantly more accurate in regions of high reddening. These dust maps will also be useful for estimating millimeter emission that contaminates cosmic microwave background radiation experiments and for estimating soft X-ray absorption. We describe how to access our maps readily for general use.

15,988 citations


"Spectral energy distributions and m..." refers methods in this paper

  • ...All SDSS magnitudes have been corrected for Galactic extinction according to Schlegel et al. (1998)....

    [...]

Journal ArticleDOI
TL;DR: In this paper, the authors presented a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed.
Abstract: We present a full sky 100 micron map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 micron and 240 micron data, we have constructed a map of the dust temperature, so that the 100 micron map can be converted to a map proportional to dust column density. The result of these manipulations is a map with DIRBE-quality calibration and IRAS resolution. To generate the full sky dust maps, we must first remove zodiacal light contamination as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 micron DIRBE map against the Leiden- Dwingeloo map of H_I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 micron flux. For the 100 micron map, no significant CIB is detected. In the 140 micron and 240 micron maps, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 \pm 13 nW/m^2/sr at 140 micron, and 17 \pm 4 nW/m^2/sr at 240 micron (95% confidence). This integrated flux is ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles estimates in regions of low and moderate reddening. These dust maps will also be useful for estimating millimeter emission that contaminates CMBR experiments and for estimating soft X-ray absorption.

14,295 citations

Journal ArticleDOI
TL;DR: In this article, the authors find that the emerging standard model of cosmology, a flat -dominated universe seeded by a nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data.
Abstract: WMAP precision data enable accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat � -dominated universe seeded by a nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data. For the WMAP data only, the best-fit parameters are h ¼ 0:72 � 0:05, � bh 2 ¼ 0:024 � 0:001, � mh 2 ¼ 0:14 � 0:02, � ¼ 0:166 þ0:076 � 0:071 , ns ¼ 0:99 � 0:04, and � 8 ¼ 0:9 � 0:1. With parameters fixed only by WMAP data, we can fit finer scale cosmic microwave background (CMB) measure- ments and measurements of large-scale structure (galaxy surveys and the Lyforest). This simple model is also consistent with a host of other astronomical measurements: its inferred age of the universe is consistent with stellar ages, the baryon/photon ratio is consistent with measurements of the (D/H) ratio, and the inferred Hubble constant is consistent with local observations of the expansion rate. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements, and Lyforest data to find the model's best-fit cosmological parameters: h ¼ 0:71 þ0:04 � 0:03 , � bh 2 ¼ 0:0224 � 0:0009, � mh 2 ¼ 0:135 þ0:008 � 0:009 , � ¼ 0:17 � 0:06, ns(0.05 Mpc � 1 )=0 :93 � 0:03, and � 8 ¼ 0:84 � 0:04. WMAP's best determination of � ¼ 0:17 � 0:04 arises directly from the temperature- polarization (TE) data and not from this model fit, but they are consistent. These parameters imply that the age of the universe is 13:7 � 0:2 Gyr. With the Lyforest data, the model favors but does not require a slowly varying spectral index. The significance of this running index is sensitive to the uncertainties in the Ly� forest. By combining WMAP data with other astronomical data, we constrain the geometry of the universe, � tot ¼ 1:02 � 0:02, and the equation of state of the dark energy, w < � 0:78 (95% confidence limit assuming w �� 1). The combination of WMAP and 2dFGRS data constrains the energy density in stable neutrinos: � � h 2 < 0:0072 (95% confidence limit). For three degenerate neutrino species, this limit implies that their mass is less than 0.23 eV (95% confidence limit). The WMAP detection of early reionization rules out warm dark matter. Subject headings: cosmic microwave background — cosmological parameters — cosmology: observations — early universe On-line material: color figure

10,650 citations


"Spectral energy distributions and m..." refers methods in this paper

  • ...Throughout this paper we use a CDM cosmology with H0 ¼ 70 km s 1 Mpc 1, ¼ 0:7, and m ¼ 0:3, consistent with the WMAP cosmology (Spergel et al. 2003, 2006)....

    [...]

Journal ArticleDOI
TL;DR: The Sloan Digital Sky Survey (SDSS) as mentioned in this paper provides the data to support detailed investigations of the distribution of luminous and non-luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands.
Abstract: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey of the approximately one million brightest galaxies and 10^5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS, and serves as an introduction to extensive technical on-line documentation.

10,039 citations

Journal ArticleDOI
Donald G. York1, Jennifer Adelman2, John E. Anderson2, Scott F. Anderson3  +148 moreInstitutions (29)
TL;DR: The Sloan Digital Sky Survey (SDSS) as discussed by the authors provides the data to support detailed investigations of the distribution of luminous and non-luminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag.
Abstract: The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ~ 23 mag, and a spectroscopic survey of the approximately 106 brightest galaxies and 105 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS and serves as an introduction to extensive technical on-line documentation.

9,835 citations


"Spectral energy distributions and m..." refers methods in this paper

  • ...…Hatziminaoglou et al. (2005) investigated the combined optical + MIR color distribution of quasars by combining data from the ELAIS-N1 field in the SpitzerWide-Area Infrared Extragalactic Survey (SWIRE; Lonsdale et al. 2003) with data from the Sloan Digital Sky Survey (SDSS; York et al. 2000)....

    [...]

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Frequently Asked Questions (1)
Q1. What contributions have the authors mentioned in the paper "Spectral energy distributions and multiwavelength selection of type 1 quasars" ?

The authors present an analysis of the mid-infrared ( MIR ) and optical properties of type 1 ( broad-line ) quasars detected by the Spitzer Space Telescope. The authors demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei ( AGNs ) than MIR or optical colors alone. The authors discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates ; assuming themeanSED can lead to errors as large as 50 % for individual quasars when inferring a bolometric luminosity from an optical luminosity. Finally, the authors show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened /obscured AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio.