J/ApJ/748/131 MgII absorbers in SDSS-DR7 quasar catalog (Shen+, 2012)
On the link between associated Mg II absorbers and star formation in quasar
hosts.
Shen Y., Menard B.
<Astrophys. J., 748, 131 (2012)>
=2012ApJ...748..131S 2012ApJ...748..131S
ADC_Keywords: QSOs ; Redshifts ; Equivalent widths
Keywords: black hole physics - galaxies: active - quasars: absorption lines -
quasars: general
Abstract:
A few percent of quasars show strong associated Mg II absorption, with
velocities (voff) lying within a few thousand km/s from the quasar
systemic redshift. These associated absorption line (AAL) systems are
usually interpreted as absorbers that are either intrinsic to the
quasar and its host, or arising from external galaxies clustering
around the quasar. Using composite spectra of ∼1800 Mg II AAL quasars
selected from SDSS DR7 at 0.4≲z≲2, we show that quasars with AALs
with voff<1500km/s have a prominent excess in [OII]λ3727
emission (detected at >7σ) at rest relative to the quasar host,
compared to unabsorbed quasars. We interpret this [OII] excess as due
to enhanced star formation in the quasar host. Our results suggest
that a significant fraction of AALs with voff<1500km/s are
physically associated with the quasar and its host. AAL quasars also
have dust reddening lying between normal quasars and the so-called
dust-reddened quasars. We suggest that the unique properties of AAL
quasars can be explained if they are the transitional population from
heavily dust-reddened quasars to normal quasars in the formation
process of quasars and their hosts. This scenario predicts a larger
fraction of young bulges, disturbed morphologies, and interactions of
AAL quasar hosts compared to normal quasars. The intrinsic link
between associated absorbers and quasar hosts opens a new window to
probe massive galaxy formation and galactic-scale feedback processes,
and provides a crucial test of the evolutionary picture of quasars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 1937 The sample of associated absorption line
systems (AALs), identified from SDSS-DR7 QSOs
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See also:
VII/269 : SDSS Quasar Catalog, DR9Q (Paris+, 2012)
J/PASJ/65/8 : Catalog of SDSS quasar absorption redshift (Qin+, 2013)
J/AJ/141/137 : Pittsburgh SDSS Mg II QSO catalog (Quider+, 2011)
J/ApJ/732/110 : SDSS 2175Å extinction bump candidates (Jiang+, 2011)
J/ApJ/714/1521 : Spectroscopy of galaxies around distant QSOs (Chen+, 2010)
J/MNRAS/405/2302 : Improved redshifts for SDSS quasar spectra (Hewett+, 2010)
J/ApJ/698/819 : MgII and LRGs cross-correlation analysis (Lundgren+, 2009)
J/ApJ/679/239 : Associated MgII absorbers (Vanden+, 2008)
J/AJ/106/848 : QSO MgII absorption line systems (Drinkwater+, 1993)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS SDSS-DR7 designation (HHMMSS.ss+DDMMSS.s; J2000)
20- 23 I4 --- Plate SDSS-DR7 Plate number
25- 27 I3 --- Fib SDSS-DR7 Fiber number
29- 33 I5 --- MJD Modified Julian Date
35- 40 F6.4 --- z [0.3/2.3] Catalogued SDSS-DR7 redshift
42- 45 F4.2 0.1nm W2796 [0.1/6.9] Restframe equivalent width of MgII(2796)
47- 50 F4.2 0.1nm e_W2796 Restframe equivalent width error of MgII(2796)
52- 55 F4.2 0.1nm W2803 [0.1/6.7] Restframe equivalent width of MgII(2803)
57- 60 F4.2 0.1nm e_W2803 Restframe equivalent width error of MgII(2803)
62- 66 I5 km/s Voff1 [-2969/2999] Absorber velocity offset based on
fiducial systemic redshift (1)
68- 72 I5 km/s Voff2 [-4171/4407] Absorber velocity offset based on
SDSS systemic redshift (1)
74- 78 I5 km/s Voff3 [-3385/4709] Absorber velocity offset based on
H&W systemic redshift (1)
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Note (1): We list the absorber velocity offset calculated from the fiducial
systemic velocity (based on the broad MgII centroid), the SDSS redshift
in the DR7 quasar catalog (Cat. VII/260; superseded by Cat. VII/269),
and the improved redshift from Hewett & Wild (2011, J/MNRAS/405/2302).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Oct-2013