J/MNRAS/495/2342 GRB hydrogen column densities (Dalton+, 2020)
Using realistic host galaxy metallicities to improve the GRB X-ray equivalent
total hydrogen column density and constrain the intergalactic medium density.
Dalton T., Morris S.L.
<Mon. Not. R. Astron. Soc., 495, 2342-2353 (2020)>
=2020MNRAS.495.2342D 2020MNRAS.495.2342D (SIMBAD/NED BibCode)
ADC_Keywords: GRB ; H I data ; X-ray sources ; Radio sources
Keywords: gamma-ray burst: general - galaxies: abundances -
galaxies: high-redshift - intergalactic medium -
cosmological parameters - X-rays: general
Abstract:
It is known that the GRB equivalent hydrogen column density (NHX)
changes with redshift and that, typically, NHX is greater than the
GRB host neutral hydrogen column density. We have compiled a large
sample of data for GRB NHX and metallicity [X/H]. The main aims of
this paper are to generate improved NHX for our sample by using
actual metallicities, dust corrected where available for detections,
and for the remaining GRB, a more realistic average intrinsic
metallicity using a standard adjustment from solar. Then, by
approximating the GRB host intrinsic hydrogen column density using the
measured neutral column (NHI,IC) adjusted for the ionization
fraction, we isolate a more accurate estimate for the intergalactic
medium (IGM) contribution. The GRB sample mean metallicity is
=-1.17±0.09 rms (or 0.07±0.05 Z/Zsol) from a sample of 36 GRB
with a redshift 1.76≤z≤5.91, substantially lower than the assumption
of solar metallicity used as standard for many fitted NHX. Lower GRB
host mean metallicity results in increased estimated NHX with the
correction scaling with redshift as
Δlog(NHXcm-2)=(0.59±0.04)log(1+z)+0.18±0.02. Of the 128
GRB with data for both NHX and NHI,IC in our sample, only six have
NHI,IC>NHX when revised for realistic metallicity, compared to 32
when solar metallicity is assumed. The lower envelope of the revised
NHX-NHI,IC, plotted against redshift can be fit by
log(NHX-NHI,ICcm-2)=20.3+2.4log(1+z). This is taken to be an
estimate for the maximum IGM hydrogen column density as a function of
redshift. Using this approach, we estimate an upper limit to the
hydrogen density at redshift zero (n0) to be consistent with
n0=0.17x10-7cm-3.
Description:
We compiled a large sample of all Swift X-ray Telescope observed GRB
with spectroscopic redshifts up to 2019 July 31 (with a photometric
redshift only for GRB090429B). Of this sample of 352 GRB with fitted
X-ray equivalent hydrogen column densities, 128 have also have
intrinsic neutral hydrogen column density measurements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 72 363 The GRB full sample
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- GRB GRB name
9- 12 F4.2 --- z Spectroscopic redshift
14- 18 F5.2 [cm-2] logNHX ? Equivalent hydrogen column density
20- 23 F4.2 [cm-2] E_logNHX ? Error on logNHX (upper value)
25- 29 F5.2 [cm-2] e_logNHX ? Error on logNHX (lower value)
31- 35 A5 --- r_logNHX Reference for logNHX (1)
37- 41 F5.2 [cm-2] logNHI-IC ? HI column density (from Tanvir et al.,
2019MNRAS.483.5380T 2019MNRAS.483.5380T)
43- 46 F4.2 [cm-2] e_logNHI-IC ? Error on logNHI-IC
48- 49 A2 --- n_logNHI-IC [IC ] IC for corrected for ionization
fraction
51- 52 A2 --- l_[X/H] [< >=] Limit flag on [X/H]
54- 58 F5.2 [-] [X/H] ? Metal abundance
60- 63 F4.2 [-] E_[X/H] ? Error on [X/H] (upper value)
65- 68 F4.2 [-] e_[X/H] ? Error on [X/H] (lower value)
70- 72 A3 --- r_[X/H] Reference for [X/H] (1)
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Note (1): References as follows:
A16 = Rosen et al., 2016A&A...590A...1R 2016A&A...590A...1R
LJ15 = Littlejohns et al., 2015MNRAS.449.2919L 2015MNRAS.449.2919L
S15 = Journal of High Energy Astrophysics, 7, 35
Swift = Swift
Z18 = Zafar et al., 2018MNRAS.479.1542Z 2018MNRAS.479.1542Z
A18 = Arabsalmani et al., 2018MNRAS.473.3312A 2018MNRAS.473.3312A
B19 = Bolmer et al., 2019A&A...623A..43B 2019A&A...623A..43B
C15 = Cucchiara et al., 2015ApJ...804...51C 2015ApJ...804...51C
H19 = Heintz et al., 2019A&A...629A.131H 2019A&A...629A.131H
V17 = Vergani et al., 2017A&A...599A.120V 2017A&A...599A.120V
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Jun-2023