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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
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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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)
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.
Byte-by-byte Description of file: table3.dat table4.dat table5.dat
Bytes Format Units Label Explanations
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 c_1_ parameter (2) 55- 58 F4.2 mag e_c1 c1 uncertainty 60- 64 F5.2 mag c2 c_2_ parameter (2) 66- 69 F4.2 mag e_c2 c2 uncertainty 71- 74 F4.2 mag c3 c_3_ parameter (2) 76- 79 F4.2 mag e_c3 c3 uncertainty 81- 84 F4.2 um-1 x0 Peak position of Drude profile (x_0_) (2) 86- 89 F4.2 um-1 e_x0 x0 uncertainty 91- 94 F4.2 um-1 gamma FWHM of Drude profile (gamma) (2) 96- 99 F4.2 um-1 e_gamma ? Uncertainty in gamma 101-104 F4.2 --- Chi2 χ2ν 106-108 F3.1 --- Sig Significance (sigma) (3)
Note (1): The expected typical error is of 0.3 Angstroms. Note (2): We use a parameterized extinction curve (Fitzpatrick & Massa 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, is used to derive the statistical significance of the candidate 2175Å bumps.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Nov-2012
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