J/MNRAS/464/4545 Gamma Ray Bursts detected by Swift (2004-2015) (Buchner+, 2017)
Galaxy gas as obscurer.
I. GRBs X-ray galaxies and find an NH3 ∝ M* relation.
Buchner J., Schulze S., Bauer F.
<Mon. Not. R. Astron. Soc. 464, 4545 (2017)>
=2017MNRAS.464.4545B 2017MNRAS.464.4545B (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Abundances
Keywords: gamma-ray burst: general - galaxies: ISM - Magellanic Clouds -
galaxies: structure - X-rays: galaxies - X-rays: ISM
Abstract:
An important constraint for galaxy evolution models is how much gas
resides in galaxies, in particular, at the peak of star formation
z=1-3. We attempt a novel approach by letting long-duration gamma ray
bursts (LGRBs) x-ray their host galaxies and deliver column densities
to us. This requires a good understanding of the obscurer and biases
introduced by incomplete follow-up observations. We analyse the X-ray
afterglow of all 844 Swift LGRBs to date for their column density NH.
To derive the population properties, we propagate all uncertainties in
a consistent Bayesian methodology. The NH distribution covers the
1020-23%cm-2^ range and shows no evolutionary effect. Higher
obscurations, e.g. Compton-thick columns, could have been detected but
are not observed. The NH distribution is consistent with sources
randomly populating a ellipsoidal gas cloud of major axis
NHmajor=1023cm-2 with 0.22dex intrinsic scatter between
objects. The unbiased SHOALS survey of afterglows and hosts allows us
to constrain the relation between Spitzer-derived stellar masses and
X-ray derived column densities NH. We find a well-constrained
power-law relation of NH=1021.7cm-2x(M*/109.5M☉)1/3,
with 0.5dex intrinsic scatter between objects. The Milky Way and the
Magellanic clouds also follow this relation. From the geometry of the
obscurer, its stellar mass dependence and comparison with local
galaxies, we conclude that LGRBs are primarily obscured by
galaxy-scale gas. Ray tracing of simulated Illustris galaxies reveals
a relation of the same normalization, but a steeper stellar-mass
dependence and mild redshift evolution. Our new approach provides
valuable insight into the gas residing in high-redshift galaxies.
Description:
Gamma Ray Bursts (GRB) typically show intrinsic LOS column densities
of 1021-23cm2. We performed a thorough statistical analysis of
all available X-ray spectra of Swift-detected GRBs. In the associated
paper we use sub-samples to analyse the population properties of LGRB
and concluded that the obscuration is due to large-scale gas inside
the GRB host galaxy, due to the shape of the column density
distribution and its correlation with host stellar mass.
This catalogue presents X-ray spectral analysis of all Swift-detected
GRBs. It includes information about the GRB (ID, Swift Trigger ID,
duration, RA/Dec in J2000, galactic coordinates, Milky Way column
density). Those properties are taken from the http://www.swift.ac.uk/
and http://gcn.gsfc.nasa.gov/ websites. We removed prompt emission and
flares, leaving only a certain time interval for spectral extraction.
We use two models to analyse X-ray spectra: TBABS and SPHERE. Both
include updated abundances and cross-sections as compared to previous
works. The latter includes the effects of Compton-scattering and FeKa
fluorescence relevant at high column densities. Columns list the
posterior mean, standard deviation, 10% and 90% quantiles.
Note that the column densities are converted to hydrogen assuming
local ISM abundances, but are derived primarily from photo-electric
absorption of e.g. Fe and O, and therefore primarily measure metal
gas.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
grbcat.dat 270 920 Catalog of SWIFT GRB (2004-2015)
grbcat.fits 2880 88 FITS version of the catalog
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See also:
IX/43 : 1SXPS Swift X-ray telescope point source catalog (Evans+ 2014)
J/A+A/510/A48 : Palermo Swift-BAT Hard X-ray Catalogue (Cusumano+, 2010)
J/A+A/528/A122 : SwiftFT catalog (Puccetti+, 2011)
J/ApJS/195/2 : The second Swift BAT GRB catalog (BAT2) (Sakamoto+, 2011)
J/ApJS/201/34 : Swift-INTEGRAL X-ray (SIX) survey (Bottacini+, 2012)
J/ApJS/209/20 : Swift GRB catalog with X-ray data (Grupe+, 2013)
J/A+A/551/A142 : 7 year Swift-XRT point source catalog (1SWXRT) (D'Elia+, 2013)
J/A+A/562/A2 : 100-month Swift catalogue of SFXTs (Romano+, 2014)
Byte-by-byte Description of file: grbcat.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name GRB ID (GRB YYMMDDA)
13- 20 I8 --- Trigger Swift Trigger ID
22- 33 E12.6 s Dur ?=-1 Duration
35 I1 --- is_short [0/1] 1 if T90>2s
37- 45 F9.5 deg RAdeg Right ascension (J2000)
47- 56 F10.6 deg DEdeg Declination (J2000)
58- 66 F9.5 deg GLON Galactic longitude
68- 77 F10.6 deg GLAT Galactic latitude
79- 90 E12.6 [cm-2] NHgal Galactic column density
92- 99 F8.6 --- z Redshift
101-152 A52 s Tint Time interval(s) used for X-ray
spectral extraction
154-161 F8.4 [cm-2] NHT ?=-99 Posterior mean column density derived
using tbabs obscurer model
163-172 F10.6 [cm-2] e_NHT ?=-99 Standard deviation of NHT
174-181 F8.4 [cm-2] NHTq10 ?=-99 10% quantile of posterior NHT
183-190 F8.4 [cm-2] NHTq90 ?=-99 90% quantile of posterior NHT
192-200 F9.5 --- PhoIndexT ?=-99 Mean spectral slope, E-γ
202-211 F10.6 --- e_PhoIndexT ?=-99 Standard deviation of PhoIndexT
213-220 F8.4 [cm-2] NHS ?=-99 Posterior mean column density derived
using sphere obscurer model
222-231 F10.6 [cm-2] e_NHS ?=-99 Standard deviation of NHS
233-240 F8.4 [cm-2] NHSq10 ?=-99 10% quantile of posterior NHS
242-249 F8.4 [cm-2] NHSq90 ?=-99 90% quantile of posterior NHS
251-259 F9.5 --- PhoIndexS ?=-99 Mean spectral slope, E-γ
261-270 F10.6 --- e_PhoIndexS ?=-99 Standard deviation of PhoIndexTS
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Acknowledgements:
Johannes Buchner, johannes.buchner.acad(at)gmx.com
(End) Patricia Vannier [CDS] 16-Apr-2016