J/MNRAS/464/L56 DLA properties and EW of 36 QSOs (Berg+, 2017)
On the selection of damped Lyman α systems using Mg II absorption
at 2 < zabs < 4.
Berg T.A.M., Ellison S.L., Prochaska J.X., Sanchez-Ramirez R., Lopez S.,
D'Odorico V., Becker G., Christensen L., Cupani G., Denney K., Worseck G.
<Mon. Not. R. Astron. Soc., 464, L56-60 (2017)>
=2017MNRAS.464L..56B 2017MNRAS.464L..56B (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Redshifts ; Equivalent widths
Keywords: galaxies: abundances - galaxies: high-redshift - galaxies: ISM -
quasars: absorption lines
Abstract:
The XQ-100 survey provides optical and near-infrared coverage of 36
blindly selected, intervening damped Lyman α systems (DLAs) at
2<zabs<4, simultaneously covering the MgII doublet at
λλ2796,2803Å, and the Lyα transition. Using
the XQ-100 DLA sample, we investigate the completeness of selecting
DLA absorbers based on their MgII rest-frame equivalent width
(W02796) at these redshifts. Of the 29 DLAs with clean Mg II
profiles, we find that six (20 per cent of DLAs) have
W02796<0.6Å. The DLA incidence rate of W02796<0.6Å
absorbers is a factor of ∼5 higher than what is seen in z∼1 samples,
indicating a potential evolution in the MgII properties of DLAs with
redshift. All of the W02796<0.6Å DLAs have low metallicities
(-2.5<[M/H]←1.7), small velocity widths (v90<50km/s), and tend to
have relatively low N(HI). We demonstrate that the exclusion of these
low W02796 DLAs results in a higher mean N(HI) which in turn leads
to an ∼7 per cent increase in the cosmological gas density of HI of
DLAs at 2<zabs<4; and that this exclusion has a minimal effect on
the HI-weighted mean metallicity.
Description:
The XQ-100 Legacy Survey observed 100 QSOs with the X-Shooter
spectrograph on the Very Large Telescope, providing simultaneous
wavelength coverage from 3150Å-25000Å at a full width at
half-maximum (FWHM) resolution R∼5000-9000. For more details on the
observations, see Lopez et al. (2016A&A...594A..91L 2016A&A...594A..91L). We emphasize
that the 100 QSO targets were not pre-selected to contain DLAs, thus
providing a 'blind' sample of DLAs along the lines of sight.
Table 1 contains a summary of the intervening DLAs, including the
measured rest-frame EW for the MgII 2796Å and 2803Å lines, as
well as the FeII 2600Å line (with EW W02600).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 99 36 DLA properties and equivalent widths
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See also:
J/MNRAS/456/4488 : XQ-100 survey neutral gas (Sanchez-Ramirez+, 2016)
J/MNRAS/462/3285 : XQ-100 targets equivalent widths (Perrotta+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- QSO QSO name (JHHMM+DDMM)
12- 15 F4.2 --- zem Emission redshift
17- 22 F6.4 --- zabs Absoprtion redshift
24- 28 F5.2 [cm-2] logN(HI) HI column density
30- 33 F4.2 [cm-2] e_logN(HI) rms uncertainty on logN(HI)
35 A1 --- l_W2796-0 Limit flag on W2796-0
36- 40 F5.3 0.1nm W2796-0 ?=- MgII 2796Å rest-frame equivalent width
42- 46 F5.3 0.1nm e_W2796-0 ? rms uncertainty on W2796-0
48 A1 --- l_W2803-0 Limit flag on W2803-0
49- 53 F5.3 0.1nm W2803-0 ?=- MgII 2803Å rest-frame equivalent width
55- 59 F5.3 0.1nm e_W2803-0 ? rms uncertainty on W2803-0
61- 65 F5.3 0.1nm W2600-0 ?=- MgII 2600Å rest-frame equivalent width
67- 71 F5.3 0.1nm e_W2600-0 ? rms uncertainty on W2600-0
73- 77 F5.2 [-] [M/H] Metallicity
79- 82 F4.2 [-] e_[M/H] rms uncertainty on [M/H]
84- 87 A4 --- El Element
89- 91 I3 km/s v90 Velocity width
93- 95 F3.1 --- D-index ?=- D-index (1)
97- 99 F3.1 --- D-indexcut Cut for D-index (2)
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Note (1): D-index defined in Ellison (2006MNRAS.368..335E 2006MNRAS.368..335E) potentially corrects
bias towards low v90, as the EW is normalized by the velocity width of the
line.
Note (2): cut is obtained from Table 2 in Ellison (2006MNRAS.368..335E 2006MNRAS.368..335E), and is
based on the resolution at the MgII 2796Å line (assuming R=5300). An
absorber with a D-index larger than the cut value would be considered a
DLA candidate.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-May-2018