J/ApJ/755/89 Metallicities of damped Lyα systems (Rafelski+, 2012)
Metallicity evolution of damped Lyα systems out to z ∼ 5.
Rafelski M., Wolfe A.M., Prochaska J.X., Neeleman M., Mendez A.J.
<Astrophys. J., 755, 89 (2012)>
=2012ApJ...755...89R 2012ApJ...755...89R
ADC_Keywords: Abundances ; Photometry, SDSS ; Redshifts ; QSOs ;
Equivalent widths
Keywords: Galaxy: halo; galaxies: abundances; galaxies: evolution;
galaxies: general; galaxies: ISM; quasars: absorption lines
Abstract:
We present chemical abundance measurements for 47 damped Lyα
(DLA) systems, 30 at z>4, observed with the Echellette Spectrograph
and Imager and the High Resolution Echelle Spectrometer on the Keck
telescopes. H I column densities of the DLAs are measured with Voigt
profile fits to the Lyα profiles, and we find an increased
number of false DLA identifications with Sloan Digital Sky Survey at
z>4 due to the increased density of the Lyα forest. Ionic column
densities are determined using the apparent optical depth method, and
we combine our new metallicity measurements with 195 from previous
surveys to determine the evolution of the cosmic metallicity of
neutral gas. We find the metallicity of DLAs decreases with increasing
redshift, improving the significance of the trend and extending it to
higher redshifts, with a linear fit of -0.22±0.03 dex per unit
redshift from z=0.09-5.06. The metallicity "floor" of ~1/600
solar continues out to z∼5, despite our sensitivity for finding DLAs
with much lower metallicities. However, this floor is not
statistically different from a steep tail to the distribution. We also
find that the intrinsic scatter of metallicity among DLAs of ∼0.5dex
continues out to z∼5. In addition, the metallicity distribution and
the α/Fe ratios of z>2 DLAs are consistent with being drawn from
the same parent population with those of halo stars. It is therefore
possible that the halo stars in the Milky Way formed out of gas that
commonly exhibits DLA absorption at z>2.
Description:
The first sample of targets was drawn from the SDSS-DR3 and SDSS-DR5
surveys for DLA systems performed by Prochaska et al. (2005,
Cat. J/ApJ/635/123) and Prochaska & Wolfe (2009ApJ...696.1543P 2009ApJ...696.1543P),
respectively. We restricted the list to sources that were sufficiently
bright such that we could obtain S/N>15 spectra in a non-prohibitive
observing time. After the first few nights, we needed to supplement
the sample with additional z>4 DLAs, and we searched for new z>4
quasars from SDSS-DR7.
In addition to this primary high-redshift quasar sample obtained in
2009-2011, we also include new observations of lower redshift quasars
(2.5≲z≲3.5) obtained in 2008 to augment the number of unbiased
metallicity measurements. The new observations comprise a total of six
nights on the Echellette Spectrograph and Imager (ESI) and seven
nights on High Resolution Echelle Spectrometer (HIRES) on the Keck I
and II 10m telescopes. In Table 1 we present a journal of observations
describing the 50 quasars in our sample.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 102 72 Journal of observations
table2.dat 85 47 New DLA metallicities
table3.dat 99 195 Literature DLA metallicities
table4.dat 94 639 Ionic column densities
refs.dat 67 56 References
--------------------------------------------------------------------------------
See also:
VII/270 : SDSS quasar catalog: tenth data release (Paris+, 2014)
VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron+ 2010)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/A+A/547/L1 : SDSS-III DR9 DLA catalogue (Noterdaeme+, 2012)
J/A+A/530/A33 : Evolutionary tracks to estimate DLA depletions (Vladilo+,
2011)
J/ApJ/721/1 : Keck ESI observations of Lyα systems (Penprase+, 2010)
J/ApJ/683/321 : Metallicities of GRB, DLA, & Lyα galaxies (Fynbo+, 2008)
J/ApJ/675/1002 : Proximate DLA systems in SDSS-DR5 (Prochaska+, 2008)
J/ApJS/171/29 : UCSD/Keck DLA Abundance Database (Prochaska+, 2007)
J/A+A/473/791 : CIV absorption in DLAs and sub-DLAs systems (Fox+, 2007)
J/ApJ/636/610 : Damped Lyα systems at z<1.65 (Rao+, 2006)
J/ApJ/635/123 : The SDSS-DR3 damped Lyα survey (Prochaska+, 2005)
J/AJ/130/1345 : Optical-infrared colors of CORALS QSOs (Ellison+, 2005)
J/MNRAS/354/L31 : SDSS DR2 QSO and DLA properties (Murphy+, 2004)
J/PASP/116/622 : SDSS damped Lyα survey: DR1 (Prochaska+, 2004)
J/A+A/370/426 : APM BR J0307-4945 UVES spectrum (Dessauges-Zavadsky+, 2001)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- QSO QSO name (JHHMM+DDMM)
12- 13 I2 h RAh Hour of Right Ascension (J2000)
15- 16 I2 min RAm Minute of Right Ascension (J2000)
18- 21 F4.1 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- Sign of the Declination (J2000)
24- 25 I2 deg DEd Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of Declination (J2000)
33- 37 F5.2 mag rmag [17.5/21.7] SDSS-DR7 r-band AB magnitude
(Cat. II/294)
39- 43 F5.2 mag imag SDSS-DR7 i band AB magnitude (Cat. II/294)
45- 48 F4.2 --- zem [2.5/5.4] QSO emission line redshift
50- 69 A20 --- zabs Absorption line redshift(s) (1)
71- 81 A11 "YYYY/MMM/DD" Date UT Date of observation
83- 88 A6 --- Inst Instrument used (G1)
90- 93 F4.2 arcsec Slit [0.5/0.9] Slit width used
95- 99 I5 s Exp [900/17400] Exposure time
101-102 I2 pix-1 SN [4/40]? Signal-to-noise per pixel (2)
--------------------------------------------------------------------------------
Note (1): Of candidate DLAs in QSO. If marked redshift with a *, then marked
a DLA in SDSS, but is not a DLA based on higher resolution ESI data.
Note (2): Median signal-to-noise per pixel at lambda∼8300Å, except in the
HIRES observations of J1353+5328 and J1541+3153, where it is at
lambda∼7300Å.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table[23].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- QSO QSO name (1)
16- 21 F6.4 --- z [0.09/5.2] Absorption line redshift
24- 28 F5.2 [cm-2] NHI [20.3/21.9] Log of the hydrogen column density
31- 34 F4.2 [cm-2] e_NHI Error in NHI
38 I1 --- f_[a/H] ? Origin of [a/H] (2)
41- 45 F5.2 [Sun] [a/H] [-2.8/0]?=0 Log of α elements i
to hydrogen number abundance
48- 51 F4.2 [Sun] e_[a/H] Error in [a/H]
55 I1 --- f_[Fe/H] ? Origin of [Fe/H] (3)
58- 62 F5.2 [Sun] [Fe/H] [-3/0]?=0 Log of iron to hydrogen number
abundance
65- 68 F4.2 [Sun] e_[Fe/H] Error in [Fe/H]
72 I1 --- f_[M/H] Origin of [M/H] (4)
75- 79 F5.2 [Sun] [M/H] [-3/0.08] Log of "M" to hydrogen number
abundance
82- 85 F4.2 [Sun] e_[M/H] Error in [M/H]
88- 99 A12 --- Ref Reference (see refs.dat file)
--------------------------------------------------------------------------------
Note (1): In table 3, B0335-211 is very likely a misprint for B0335-122 and
PSS0134+3317 is very likely a misprint for PSSJ0134+3307.
Note (2): origin of the [α/H] estimation as follows:
0 = No measurement;
1 = Silicium Si
2 = Si lower limit;
3 = Si upper limit;
4 = Suplhur S;
5 = Oxygen 0;
6 = combined α limit.
Note (3): origin of the [Fe/H] estimation as follows:
0 = No measurement;
1 = Fe measurement;
2 = Fe lower limit;
3 = Fe upper limit;
4 = [Ni/H]∼0.1;
5 = [Cr/H]∼0.2;
6 = [Al/H];
7 = combined Fe limit.
Note (4): origin of the [M/H] estimation as follows:
1 = [α/H];
2 = [Fe/H] (in which case we use [M/H]=[Fe/H]+0.3);
3 = combined [α/H] limits;
4 = combined [Fe/H] limits.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- QSO QSO name (JHHMM+DDMM)
12- 17 F6.4 --- z [2.4/5.2] Absorption line redshift
19- 24 A6 --- Ion Ion name
26- 34 F9.4 0.1nm lambda [1250/2261] Rest-frame wavelength of Ion (Å)
36- 42 F7.4 [-] logf [-2.9/0.3] Log of oscillator strength
44- 48 A5 --- Inst Instrument used for measurement (G1)
50- 53 I4 km/s Vmin [-500/50]? Lower velocity interval of
measurement (1)
55- 57 I3 km/s Vmax [10/500]? Upper velocity interval of
measurement (1)
59 A1 --- l_EW Limit flag on EW
60- 65 F6.1 10-13m EW [3/2832]? Rest equivalent width (mÅ)
67- 70 F4.1 10-13m e_EW ? Error in EW (mÅ)
72 A1 --- l_MIon Limit flag on MIon
73- 77 F5.2 cm-2 MIon [11.8/16.2] Measured column density of Ion
79- 82 F4.2 cm-2 e_MIon ? Error in MIon
84 A1 --- l_NIon Limit flag on NIon
85- 89 F5.2 cm-2 NIon ? Adopted column density of Ion
91- 94 F4.2 cm-2 e_NIon ? Error in NIon
--------------------------------------------------------------------------------
Note (1): Velocity interval over which the equivalent width and column
density are measured.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode Bibcode
24- 48 A25 --- Aut Author's name(s)
50- 67 A18 --- Comm Comment
--------------------------------------------------------------------------------
Global Notes:
Note (G1): the instruments (used on the Keck telescope) are:
ESI = Echellette Spectrograph and Imager
HIRES = High Resolution Echelle Spectrometer
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 10-Mar-2014