J/ApJ/772/26 AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)
Mid-infrared selection of active galactic nuclei with the Wide-field Infrared
Survey Explorer.
II. Properties of WISE-selected active galactic nuclei in the NDWFS Bootes
field.
Assef R.J., Stern D., Kochanek C.S., Blain A.W., Brodwin M., Brown M.J.I.,
Donoso E., Eisenhardt P.R.M., Jannuzi B.T., Jarrett T.H., Stanford S.A.,
Tsai C.-W., Wu J., Yan L.
<Astrophys. J., 772, 26 (2013)>
=2013ApJ...772...26A 2013ApJ...772...26A (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Photometry, infrared ; Redshifts ;
Spectroscopy ; Reddening
Keywords: galaxies: active; methods: statistical; quasars: general
Abstract:
Stern et al. (2012ApJ...753...30S 2012ApJ...753...30S, Paper I) presented a study of
Wide-field Infrared Survey Explorer (WISE) selection of active
galactic nuclei (AGNs) in the 2deg2 COSMOS field, finding that a
simple criterion W1-W2≥0.8 provides a highly reliable and complete
AGN sample for W2<15.05, where the W1 and W2 passbands are centered at
3.4µm and 4.6µm, respectively. Here we extend this study using
the larger 9deg2 NOAO Deep Wide-Field Survey Bootes field which also
has considerably deeper WISE observations than the COSMOS field, and
find that this simple color cut significantly loses reliability at
fainter fluxes. We define a modified selection criterion combining the
W1-W2 color and the W2 magnitude to provide highly reliable or highly
complete AGN samples for fainter WISE sources. In particular, we
define a color-magnitude cut that finds 130±4deg-2 AGN candidates
for W2<17.11 with 90% reliability. Using the extensive UV through
mid-IR broadband photometry available in this field, we study the
spectral energy distributions of WISE AGN candidates. We find that, as
expected, the WISE AGN selection can identify highly obscured AGNs,
but that it is biased toward objects where the AGN dominates the
bolometric luminosity output. We study the distribution of reddening
in the AGN sample and discuss a formalism to account for sample
incompleteness based on the step-wise maximum-likelihood method of
Efstathiou et al. The resulting dust obscuration distributions depend
strongly on AGN luminosity, consistent with the trend expected for a
receding torus. At LAGN∼3x1044erg/s, 29%±7% of AGNs are observed
as Type 1, while at ∼4x1045erg/s the fraction is 64%±13%. The
distribution of obscuration values suggests that dust in the torus is
present as both a diffuse medium and in optically thick clouds.
Description:
To highlight the power of WISE in finding highly obscured quasars, we
obtained spectroscopy of 12 AGN candidates at the Keck Observatory in
2011 April.
We observed three Keck slit masks in the Bootes field with the DEep
Imaging Multi-Object Spectrograph (DEIMOS) on UT 2011 April 1-3
(R∼1600). We observed a single additional mask using the dual-beam Low
Resolution Imaging Spectrometer (LRIS) on UT 2011 April 28 (R∼500 on
the blue arm and R∼700 on the red arm).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 115 12 Summary of obscured AGN candidates observed
with Keck/DEIMOS
table6.dat 128 140 Additional results from Keck observations
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/290 : SWIRE Photometric Redshift Catalogue (Rowan-Robinson+, 2008)
J/AJ/144/49 : Quasars from SDSS-DR7, WISE and UKIDSS surveys (Wu+, 2012)
J/ApJS/200/8 : AGES: the AGN and Galaxy Evolution Survey (Kochanek+, 2012)
J/ApJ/757/13 : IR SEDs of 24um z∼0.3-3 galaxies (Sajina+, 2012)
J/ApJ/751/52 : AGN cand. from the WISE, 2MASS, RASS (W2R) (Edelson+, 2012)
J/ApJ/713/970 : Low-resolution SED templates for AGNs & gal. (Assef+, 2010)
J/ApJ/710/1498 : QSO luminosity function at z∼4 (Glikman+, 2010)
J/ApJ/701/428 : The Spitzer Deep, Wide-Field Survey (SDWFS) (Ashby+, 2009)
J/ApJ/684/905 : z>1 clusters from IRAC Shallow Survey (Eisenhardt+, 2008)
J/AJ/133/186 : Opt. spectroscopy of 77 luminous AGNs and QSOs (Lacy+, 2007)
J/ApJS/166/470 : SDSS-Spitzer type I QSOs IR photometry (Richards+, 2006)
J/ApJ/642/673 : IR-selected obscured AGN candidates (Polletta+, 2006)
J/ApJ/641/140 : Optical counterparts in the NDWFS Bootes field (Brand+, 2006)
J/ApJ/640/167 : AGNs and ULIRGs in the CDF-South (Alonso-Herrero+, 2006)
J/ApJS/161/9 : X-ray survey of the NDWFS Bootes field (Kenter+, 2005)
J/AJ/123/1784 : 1.4 GHz imaging of the Bootes field (de Vries+, 2002)
J/ApJS/95/1 : Atlas of Quasar Energy Distributions (Elvis+ 1994)
http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/ : Explanatory
supplement to the WISE All-Sky Release
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Obscured AGN candidate name
12- 13 I2 h RAh [14] Hour of right ascension (J2000)
15- 16 I2 min RAm [27/32] Minute of right ascension (J2000)
18- 22 F5.2 s RAs Second of right ascension (J2000)
24 A1 --- DE- [+] Sign of declination (J2000)
25- 26 I2 deg DEd [33/35] Degree of declination (J2000)
28- 29 I2 arcmin DEm Arcminute of declination (J2000)
31- 35 F5.2 arcsec DEs Arcsecond of declination (J2000)
37- 41 F5.2 mag Imag [19/23.7] I-band magnitude
43- 47 F5.2 mag W2mag [14.3/15.9] WISE W2 magnitude (4.6um)
49- 52 F4.2 mag W1-W2 [0.5/2.1] W1-W2 color index
54- 58 F5.3 --- a [0.2/1] Best fit a parameter (1)
60- 64 F5.3 --- e_a [0.004/0.2] a uncertainty
66- 69 F4.2 mag E(B-V) [0.2/0.9] Reddening parameter for the
adopted redshift
71- 74 F4.2 mag e_E(B-V) [0.03/0.2] E(B-V) uncertainty
76- 80 F5.3 --- z [0.2/1.5] Measured redshift
81 A1 --- u_z Uncertainty flag on z
83 A1 --- q_z [ABF] Redshift quality flag, A=secure (G1)
85- 89 A5 --- Selec Selection criteria (2)
91-115 A25 --- Notes Notes
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Note (1): In order to reliably separate AGNs from inactive galaxies, we use the
parameter "a" defined in Equation (1): a=LAGN/(Lhost+LAGN)
where the luminosities correspond to the integrated specific
luminosities of the best-fit templates over the 0.1-30um wavelength
range for the AGN template and 0.03-30um for the host galaxy templates
(see Assef et al. 2010, Cat. J/ApJ/713/970, for details).
See sections 2.3 and 4.3 for further explanations.
Note (2): We refer to the reliability-optimized selection as R90 and R75 for
90% and 75% reliability, respectively, while C90 and C75 refer to
the completeness-optimized criteria. See section 3.2.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Type Target Type: IRAC (AGN/cluster), MIPS, WISE AGN,
XBootes or serendip
14- 15 I2 h RAh [14] Hour of Right Ascension (J2000)
17- 18 I2 min RAm [27/32] Minute of Right Ascension (J2000)
20- 24 F5.2 s RAs Second of Right Ascension (J2000)
26 A1 --- DE- [+] Sign of the Declination (J2000)
27- 28 I2 deg DEd [33/35] Degree of Declination (J2000)
30- 31 I2 arcmin DEm Arcminute of Declination (J2000)
33- 36 F4.1 arcsec DEs Arcsecond of Declination (J2000)
38- 42 F5.3 --- z [0/3.4] Spectroscopic redshift (z=0.0 for stars)
44 A1 --- q_z [AB] Quality in z (A=secure) (G1)
46- 50 A5 --- Mask Slitmask(s) description (1)
52-128 A77 --- Notes Additional spectral notes
--------------------------------------------------------------------------------
Note (1): Masks A, B and C were observed with DEIMOS, and the bracketed numbers
indicate the DEIMOS slitlet number.
--------------------------------------------------------------------------------
Global notes:
Note (G1): Quality flag is (see Section 4.4 for details):
A = unambiguous redshift determination, typically relying upon multiple
emission or absorption features.
B = less certain redshift determination, such as the robust detection of an
isolated emission line, but where the identification of the line is
uncertain (e.g., Stern et al. 2000ApJ...537...73S 2000ApJ...537...73S).
Quality flag "B" might also be assigned to a source with a robust
redshift identification, but where some uncertainty remains as to the
astrometric identity of that spectroscopic source. We consider the
quality "B" results likely to be correct, but additional spectroscopy
would be beneficial.
F = a spectroscopic redshift could not be reliably determined.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Stern et al. Paper I. 2012ApJ...753...30S 2012ApJ...753...30S
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Jan-2015