J/MNRAS/435/3306 Candidate type II QSOs in SDSS III (Alexandroff+, 2013)
Candidate type II quasars at 2 < z < 4.3 in the Sloan Digital Sky Survey III.
Alexandroff R., Strauss M.A., Greene J.E., Zakamska N.L., Ross N.P.,
Brandt W.N., Liu G., Smith P.S., Ge J., Hamann F., Myers A.D.,
Petitjean P., Schneider D.P., Yesuf H., York D.G.
<Mon. Not. R. Astron. Soc., 435, 3306-3325 (2013)>
=2013MNRAS.435.3306A 2013MNRAS.435.3306A
ADC_Keywords: QSOs ; Equivalent widths ; Photometry, infrared
Keywords: quasars: emission lines - quasars: general
Abstract:
At low redshifts, dust-obscured quasars often have strong yet narrow
permitted lines in the rest-frame optical and ultraviolet, excited by
the central active nucleus, earning the designation type II quasars.
We present a sample of 145 candidate type II quasars at redshifts
between 2 and 4.3, encompassing the epoch at which quasar activity
peaked in the universe. These objects, selected from the quasar sample
of the Baryon Oscillation Spectroscopic Survey of the Sloan Digital
Sky Survey III, are characterized by weak continuum in the rest-frame
ultraviolet (typical continuum magnitude of i∼22) and strong lines of
CIV and Lyα, with full width at half-maximum less than 2000km/s.
The continuum magnitudes correspond to an absolute magnitude of -23 or
brighter at redshift 3, too bright to be due exclusively to the host
galaxies of these objects. Roughly one third of the objects are
detected in the shorter wavelength bands of the Wide-Field Infrared
Survey Explorer survey; the spectral energy distributions of these
objects appear to be intermediate between classic type I and type II
quasars seen at lower redshift. Five objects are detected at rest
frame 6µm by Spitzer, implying bolometric luminosities of several
times 1046erg/s. We have obtained polarization measurements for two
objects; they are roughly 3 percent polarized. We suggest that these
objects are luminous quasars, with modest dust extinction
(AV∼0.5mag), whose ultraviolet continuum also includes a substantial
scattering contribution. Alternatively, the line of sight to the
central engines of these objects may be obscured by optically thick
material whose covering fraction is less than unity.
Description:
For our parent sample, we selected all BOSS objects in DR9 with both
Lyα and CIV emission-line measurements (given the BOSS
wavelength coverage, this corresponds to redshifts of z≳2.0) and a
reliable pipeline fit. From this sample, we selected only those
objects with 5σ detections in both Lyα and CIV (thus we
are insensitive to objects that emit only in Lyα, and restricted
ourselves to those objects in which both lines have FWHM<2000km/s.
We classified our type II quasar candidates, after removing the BAL
quasars and obvious NLS1, in two categories: those that showed all the
qualities of an obscured quasar (narrow emission lines, no associated
absorption, weak continuum), hereafter class A; and those with one or
more characteristics of unobscured objects (a broad component to an
emission line, an absorption feature or a strong blue continuum),
hereafter class B.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 98 145 Table of 145 class A candidate type II quasars
table3.dat 98 307 Table of 307 class B candidate type II quasars
table7.dat 82 40 All WISE matches in our class A sample
table8.dat 82 62 All WISE matches in our class B sample
--------------------------------------------------------------------------------
See also:
II/328 : AllWISE Data Release (Cutri+ 2013)
J/ApJS/199/3 : The quasars MMT-BOSS pilot survey (Ross+, 2012)
Byte-by-byte Description of file: table2.dat table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [SDSS]
5- 23 A19 --- SDSS SDSS J2000 name (JHHMMSS.ss+DDMMSS.s)
25- 33 F9.5 deg RAdeg Right ascension of source (J2000)
35- 42 F8.5 deg DEdeg Declination of source (J2000)
44- 49 F6.4 --- z Redshift of source
51- 54 I4 km/s W(CIV) Pipeline measured CIV width (1549Å)
56- 58 I3 km/s e_W(CIV) Error on W(CIV)
60- 63 F4.1 0.1nm W(CIV)r ?=- Pipeline measured rest equivalent width
65- 67 F3.1 0.1nm e_W(CIV)r ?=- Error on REWCIV
70- 76 F7.3 10-20W/m2 F(CIV) Pipeline measured CIV flux
78- 81 F4.1 10-20W/m2 e_F(CIV) Error on F(CIV)
83- 90 F8.3 10-20W/m2 F(Lya) Pipeline measured Lyman α flux
(1216Å)
92- 96 F5.2 10-20W/m2 e_F(Lya) Error on F(Lya)
98 A1 --- Note [*] indicates WISE matches (tables 7-8)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [SDSS]
5- 14 A10 --- SDSSs SDSS J2000 short name (JHHMM+DDMM)
16- 20 F5.2 mag W1mag ?=- WISE/W1 (3.5um; AB magnitudes)
22- 25 F4.2 mag e_W1mag ?=- Error on W1mag (AB magnitudes)
27- 31 F5.2 mag W2mag ?=- WISE/W2 (4.6um; AB magnitudes)
33- 36 F4.2 mag e_W2mag ?=- Error on W2mag (AB magnitudes)
38- 42 F5.2 mag W3mag ?=- WISE/W3 (11.6um; AB magnitudes)
44- 47 F4.2 mag e_W3mag ?=- Error on W3mag (AB magnitudes)
49- 53 F5.2 mag W4mag ?=- WISE/W4 (22.1um; AB magnitudes)
55- 58 F4.2 mag e_W4mag ?=- Error on W4mag (AB magnitudes)
60- 63 A4 --- --- [SDSS]
64- 82 A19 --- SDSS SDSS J2000 name (JHHMMSS.ss+DDMMSS.s)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Oct-2014