J/ApJ/833/283 HI-selected Lyman limit systems metallicities (Lehner+, 2016)
The cosmic evolution of the metallicity distribution of ionized gas traced by
Lyman limit systems.
Lehner N., O'Meara J.M., Howk J.C., Prochaska J.X., Fumagalli M.
<Astrophys. J., 833, 283-283 (2016)>
=2016ApJ...833..283L 2016ApJ...833..283L (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Redshifts ; Abundances ; Galaxies, spectra ; H I data ;
Optical
Keywords: galaxies: abundances; galaxies: halos; galaxies: high-redshift;
quasars: absorption lines
Abstract:
We present the first results from our KODIAQ Z survey aimed at
determining the metallicity distribution and physical properties of
the z≳2 partial and full Lyman limit systems (pLLSs and LLSs;
16.2≤logNHI<19), which are probed of the interface regions between
the intergalactic medium (IGM) and galaxies. We study 31 HI-selected
pLLSs and LLSs at 2.3<z<3.3 observed with Keck/HIRES in absorption
against background QSOs. We compare the column densities of metal ions
to HI and use photoionization models to assess the metallicity. The
metallicity distribution of the pLLSs/LLSs at 2.3<z<3.3 is consistent
with a unimodal distribution peaking at [X/H]~-2. The metallicity
distribution of these absorbers therefore evolves markedly with z
since at z≲1 it is bimodal with peaks at [X/H]~-1.8 and -0.3. There
is a substantial fraction (25%-41%) of pLLSs/LLSs with metallicities
well below those of damped Lyα absorbers (DLAs) at any studied z
from z≲1 to z∼2-4, implying reservoirs of metal-poor, cool, dense gas
in the IGM/galaxy interface at all z. However, the gas probed by pLLSs
and LLSs is rarely pristine, with a fraction of 3%-18% for pLLSs/LLSs
with [X/H]≤-3. We find C/α enhancement in several pLLSs and
LLSs in the metallicity range -2≲[X/H]≲-0.5, where C/α is 2-5
times larger than observed in Galactic metal-poor stars or
high-redshift DLAs at similar metallicities. This is likely caused by
preferential ejection of carbon from metal-poor galaxies into their
surroundings.
Description:
All the new data presented here are from our Keck Observatory Database
of Ionized Absorption toward Quasars (KODIAQ) database as part of our
new KODIAQ Z survey (Lehner+ 2014, J/ApJ/788/119 ; O'Meara+ 2015,
J/AJ/150/111). In short, these data were acquired with the HIgh
Resolution Echelle Spectrometer (HIRES) on the Keck I telescope on
Maunakea. These data were obtained by different PIs from different
institutions with Keck access, and hundreds of spectra of QSOs at
0<z<6 (most being at z∼2-4) were collected.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 76 247 Average velocities and column densities of
the metal ions (for 21 pLLSs and LLSs)
table2.dat 76 33 Summary of the HI parameters and metallicities
of 26 partial and full Lyman limit systems
(pLLSs and LLSs)
table6.dat 84 26 Cloudy results for 21 pLLSs and LLSs
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See also:
J/ApJ/596/768 : Optical depths in 19 QSOs (Schaye+, 2003)
J/ApJ/635/123 : The SDSS-DR3 damped Lyα survey (Prochaska+, 2005)
J/ApJ/765/137 : HST survey for Lyman limit systems. II. (O'Meara+, 2013)
J/ApJ/676/262 : PKS1302-102 intergalactic absorption system (Cooksey+, 2008)
J/ApJ/700/1299 : Gas-phase element depletions in the ISM (Jenkins, 2009)
J/ApJ/718/392 : SDSS Lyman limit systems at z∼3.5 (Prochaska+, 2010)
J/ApJ/721/1 : Keck ESI observations of Lyα systems (Penprase+, 2010)
J/ApJ/755/89 : Metallicities of damped Lyα systems (Rafelski+, 2012)
J/ApJ/770/138 : Metallicities of Lyman limit systems and DLA (Lehner+, 2013)
J/ApJ/775/78 : Lyman limit absorption systems in z∼3 QSOs (Fumagalli+, 2013)
J/MNRAS/435/482 : DLA system from SDSS DR5 (Jorgenson+, 2013)
J/ApJ/788/119 : Highly ionized gas of quasar properties (Lehner+, 2014)
J/ApJ/794/156 : MgII/FeII absorption profile for 0.3<z<1.4 gal. (Rubin+, 2014)
J/MNRAS/445/2061 : Absorption in multiphase circumgal. medium (Liang+, 2014)
J/ApJ/804/79 : HST/COS obs. of QSOs within 600kpc of M31 (Lehner+, 2015)
J/AJ/150/111 : KODIAQ DR1 (O'Meara+, 2015)
J/ApJS/221/2 : Keck+Magellan survey for LLSs. III. (Prochaska+, 2015)
J/MNRAS/458/4074 : UVES Advanced Data Products QSO Sample. VI. (Quiret+, 2016)
J/ApJ/833/270 : HI-selected-Lyman limit system metallicities (Glidden+, 2016)
J/AJ/154/114 : KODIAQ DR2 (O'Meara+, 2017)
http://koa.ipac.caltech.edu/workspace/TMP_OTW3Fi_29029/kodiaq29029.html :
KODIAQ home page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- KODIAQ Quasar designation (JHHMMSS+DDMMSSA)
17- 23 F7.5 --- zabs [2.3/3.3] Absorption redshift of LLS
25- 29 F5.2 [cm-2] logNHI [16/18.7] Log HI column density
31- 31 A1 --- f_Ion [ab] Metal line flag (1)
33- 38 A6 --- Ion Metal line
40- 43 I4 0.1nm lambda [977/1670]? Transition rest wavelength
in Angstroms
45- 47 I3 km/s vmin [-70/-10]? Minimum velocity limit
49- 50 I2 km/s vmax [10/70]? Maximum velocity limit
52- 56 F5.1 km/s va [-25.1/18.1]? Average velocity of metal line
57- 57 A1 --- u_va [:] Quality flag for va (2)
59- 62 F4.1 km/s e_va [0.1/20]? Uncertainty for va
64- 65 A2 --- l_logNa [≤> ] Limit flag for logNa (2)
66- 70 F5.2 [cm-2] logNa [10.7/14.7]? Column density of metal line
71- 71 A1 --- u_logNa [:] Quality flag for logNa (2)
73- 76 F4.2 [cm-2] e_logNa [0.01/0.2]? Uncertainty for logNa
--------------------------------------------------------------------------------
Note (1): Metal line flag as follows:
a = C IV was fitted with two components to extract reliably the column
density of the component directly associated with the LLS;
b = Corrected from mild saturation (see Savage & Sembach 1991).
Note (2): Upper limits ("<") are non-detections quoted at the 2σ
level. A ":" indicates that this quantity has a large uncertainty.
Column densities preceded by ">" are lower limits owing to saturation in
the absorption. Column densities preceded by "≤" could be somewhat
contaminated. For a given atom or ion with more than one transition, we
list in the row with no wavelength information (lambda="") the adopted
weighted average column densities and velocities.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 1 I1 --- Set 0: New sample of partial Lyman limit systems
(pLLSs) and full Lyman limit systems (LLSs);
1: Sample of pLLSs and LLSs drawn from
the literature
3- 17 A15 --- KODIAQ Quasar designation (JHHMMSS+DDMMSSA) (1)
19- 25 F7.5 --- zabs [2.1/3.3] Absorption redshift of LLS
27- 31 F5.2 [cm-2] logNHI [16/18.7] Log HI column density (2)
33- 37 F5.2 [cm-2] E_logNHI [+0.01/+0.3] Upper or symmetric uncertainty
on logNHI (3)
39- 43 F5.2 [cm-2] e_logNHI [-0.3/-0.2]? Lower uncertainty on logNHI (3)
45- 48 F4.1 km/s bHI [11/37.2]? HI velocity width, fit
49- 49 A1 --- f_bHI [:] Iterative Fit flag (2)
51- 53 F3.1 km/s e_bHI [0.1/1.2]? Uncertainty for bHI
55- 55 A1 --- l_[X/H] Limit flag for [X/H]
56- 60 F5.2 [-] [X/H] [-3.4/0.2]? Log of the ion number abundance
62- 66 F5.2 [-] E_[X/H] [0.05/0.3]? Upper or symmetric uncertainty
on [X/H] (3)
68- 72 F5.2 [-] e_[X/H] [-0.21]? Lower uncertainty on [X/H] (3)
74- 74 I1 --- Refs [1/3]? References for Literature Sample (4)
76- 76 A1 --- Notes [ab] Individual Object Notes (5)
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Note (1): Note added by CDS; 3 misprints are corrected in this table
thanks to the author:
J104019+572448 is KODIAQ J104018+572448,
J121930+495054 is KODIAQ J121930+494052 and
J044828-415728 is QSO B0002-422 at J000448-415729
(from Crighton+, 2015MNRAS.446...18C 2015MNRAS.446...18C).
Note (2): The HI absorption was fitted with a single component except
otherwise stated. For the new sample: systems with bHI values followed by
colons were fitted iteratively until a good fit was achieved; systems
with errors on the bHI values were fitted iteratively by hand and
automatically by minimizing the reduced-χ2; both solutions were
consistent and we adopted the minimized reduced-χ2 solution.
Note (3): If no lower uncertainty is given then the quoted upper uncertainty
is considered symmetric.
Note (4): Literature references as follows:
1 = Crighton et al. (2013ApJ...776L..18C 2013ApJ...776L..18C);
2 = Crighton et al. (2015MNRAS.446...18C 2015MNRAS.446...18C);
3 = Lehner et al. (2014, J/ApJ/788/119).
Note (5): Notes on sources as follows:
a = These two absorbers were analyzed separately and are only separated
by 50 km/s. Since they have similar metallicity and likely probing
the same structure, we only keep one of these for the metallicity
distribution analysis.
b = This pLLS is best fitted with two components. The total bHI and logHI
are well constrained, but the column densities in each component are
not robustly determined. Hence we treat this pLLS as a single absorber.
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- KODIAQ Quasar designation (JHHMMSS+DDMMSSA)
17- 23 F7.5 --- zabs [2.3/3.3] Absorption redshift of LLS
25- 29 F5.2 [cm-2] logNHI [16/18.7] Log HI column density
31- 31 A1 --- l_logNH Limit flag on logNH
32- 36 F5.2 [-] logNH [17.3/21.5] Log total H column density
38- 38 A1 --- l_[X/H] Limit flag on [X/H]
39- 43 F5.2 [-] [X/H] [-3.4/0.2] Log of the ion number abundance
45- 45 A1 --- l_[C/a] Limit flag on [C/a]
46- 50 F5.2 [-] [C/a] [-0.7/0.4]? Relative abundance of carbon
to α elements
52- 53 A2 --- l_logU [≤> ] Limit flag on logU
54- 58 F5.2 [-] logU [-4/-1.5] Ionization parameter
60- 60 A1 --- l_NHI/NH Limit flag on NHI/NH
61- 65 F5.1 % NHI/NH [92.7/100] Ionization fraction
67- 67 A1 --- l_T Limit flag on T
68- 70 F3.1 10+4K T [0.6/3.3] Temperature
72- 72 A1 --- l_logn Limit flag on lognH
73- 77 F5.2 [cm-3] logn [-3.3/-0.7] Log hydrogen number density
79- 79 A1 --- l_logl Limit flag on logl
80- 84 F5.2 [pc] logl [-0.5/6.3] Linear-scale of the absorber
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Acknowledgements:
Nicolas Lehner [University of Notre Dame, Indiana]
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Apr-2018