J/ApJ/732/110 SDSS 2175Å extinction bump candidates (Jiang+, 2011)
Toward detecting the 2175 Å dust feature associated with strong high-redshift
Mg II absorption lines.
Jiang P., Ge J., Zhou H., Wang J., Wang T.
<Astrophys. J., 732, 110 (2011)>
=2011ApJ...732..110J 2011ApJ...732..110J
ADC_Keywords: QSOs ; Redshifts ; Spectroscopy ; Equivalent widths ; Extinction
Keywords: dust, extinction - galaxies: ISM - quasars: absorption lines
Abstract:
We report detections of 39 2175Å dust extinction bump candidates
associated with strong MgII absorption lines at z∼1-1.8 on quasar
spectra in Sloan Digital Sky Survey (SDSS) DR3. These strong MgII
absorption line systems are detected among 2951 strong MgII absorbers
with a rest equivalent width Wrλ2796>1.0Å at 1.0<z<1.86,
which is part of a full sample of 7421 strong MgII absorbers compiled
by Prochter et al. (2006, Cat. J/ApJ/639/766). The redshift range of
the absorbers is chosen to allow the 2175Å extinction features to
be completely covered within the SDSS spectrograph operation
wavelength range. An upper limit of the background quasar emission
redshift at z=2.1 is set to prevent the Lyα forest lines from
contaminating the sensitive spectral region for the 2175Å bump
measurements. A total of 12 absorbers are detected with 2175Å bumps
at a 5σ level of statistical significance, 10 are detected at a
4σ level, and 17 are detected at a 3σ level. Most of the
candidate bumps in this work are similar to the relatively weak
2175Å bumps observed in the Large Magellanic Cloud LMC2 supershell
rather than the strong ones observed in the Milky Way.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 20 7751 Median composite DR7 quasar spectrum
table2.dat 73 220 The list of rejected candidates
table3.dat 108 12 Twelve high-confidence 2175Å absorber candidates
table4.dat 108 10 Ten median-confidence 2175Å absorber candidates
table5.dat 108 17 Seventeen low-confidence 2175Å absorber candidates
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
J/ApJS/194/42 : SDSS-DR3 MgII-based black hole masses (Rafiee+, 2011)
J/ApJ/698/819 : MgII and LRGs cross-correlation analysis (Lundgren+, 2009)
J/ApJ/679/239 : Associated MgII absorbers (Vanden+, 2008)
J/MNRAS/371/495 : Catalogue of MgII absorbers from SDSS DR3 (Bouche+, 2006)
J/MNRAS/354/L25 : MgII absorbers in SDSS QSOs (Bouche+, 2004)
J/ApJ/639/766 : SDSS-DR3 strong MgII absorbers (Prochter+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.1 0.1nm lambda [800/8550] Wavelength; in Angstroms
8- 14 F7.3 --- Flux [1.909/122.729] Monochromatic flux; arbitrary
units
16- 20 F5.3 --- e_Flux Uncertainty in Flux
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identification (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.3 --- zem [0.651/2.099] Schneider et al. 2010,
Cat. VII/260, emission line redshift
27- 31 F5.3 --- zab [1.00/1.84] Prochter et al. 2006,
Cat. J/ApJ/639/766, absorption line redshift
33- 36 F4.2 0.1nm EW MgII (2796) equivalent width; in Angstroms (1)
38- 42 F5.2 mag D(g-i) Relative (g-i) color of background quasar
44- 47 F4.2 mag e_D(g-i) Uncertainty in D(g-i)
49 A1 --- f_gamma [mu] measurement or upper limit (2)
51- 54 F4.2 um-1 gamma FWHM of Drude profile γ
56- 59 F4.2 um-1 e_gamma ? Uncertainty in gamma
61 A1 --- f_Abump [mu] measurement or upper limit (2)
63- 66 F4.2 --- Abump [0.04/6.13] Bump strength = π c3/(2γ)
68- 71 F4.2 --- e_Abump ? Uncertainty in Abump
73 A1 --- Note [a-c] Additional note (3)
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Note (1): The expected typical error is of 0.3 Angstroms.
Note (2): Flag as follows:
m = indicates gamma/Abump is a measurement;
u = indicates gamma/Abump is an upper limit.
Note (3): Note as follows:
a = at a statistical confidence level of <3σ;
b = broad absorption line quasar;
c = the quasar spectrum was trimmed a lot.
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Byte-by-byte Description of file: table3.dat table4.dat table5.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identification (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.3 --- zem [1.18/2.04] Schneider et al. 2010,
Cat. VII/260, emission line redshift
27- 31 F5.3 --- zab [1.00/1.85] Prochter et al. 2006,
Cat. J/ApJ/639/766, absorption line redshift
33- 36 F4.2 0.1nm EW MgII (2796) equivalent width; in Angstroms (1)
38- 42 F5.2 mag D(g-i) Relative (g-i) color of background quasar
44- 47 F4.2 mag e_D(g-i) Uncertainty in D(g-i)
49- 53 F5.2 mag c1 c1 parameter (2)
55- 58 F4.2 mag e_c1 c1 uncertainty
60- 64 F5.2 mag c2 c2 parameter (2)
66- 69 F4.2 mag e_c2 c2 uncertainty
71- 74 F4.2 mag c3 c3 parameter (2)
76- 79 F4.2 mag e_c3 c3 uncertainty
81- 84 F4.2 um-1 x0 Peak position of Drude profile (x0) (2)
86- 89 F4.2 um-1 e_x0 x0 uncertainty
91- 94 F4.2 um-1 gamma FWHM of Drude profile (γ) (2)
96- 99 F4.2 um-1 e_gamma ? Uncertainty in gamma
101-104 F4.2 --- Chi2 χ2ν
106-108 F3.1 --- Sig Significance (σ) (3)
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Note (1): The expected typical error is of 0.3 Angstroms.
Note (2): We use a parameterized extinction curve (Fitzpatrick & Massa
1990ApJS...72..163F 1990ApJS...72..163F) constituted by a linear component and a Drude
component to describe the optical/UV extinction curve in the rest
frame of an absorber on SDSS spectra for QAL (quasar absorption line)
systems. The linear component is used to model the underlying
extinction, while the Drude component is used to model the possible
2175Å extinction bump. The parameterized extinction curve is
written as: A(λ)=c1+c2x+c3D(x,x0,γ).
See section 2 for further explanations.
Note (3): The simulation technique developed by Jiang et al.
2010ApJ...720..328J 2010ApJ...720..328J, is used to derive the statistical significance
of the candidate 2175Å bumps.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Nov-2012