J/ApJ/802/103 Model predictions for GRB host galaxies (Trenti+, 2015)
The luminosity and stellar mass functions of GRB host galaxies: insight into
the metallicity bias.
Trenti M., Perna R., Jimenez R.
<Astrophys. J., 802, 103 (2015)>
=2015ApJ...802..103T 2015ApJ...802..103T
ADC_Keywords: Gamma rays ; Redshifts ; Stars, masses ; Abundances
Keywords: galaxies: general; galaxies: high-redshift; gamma-ray burst: general;
stars: formation
Abstract:
Long-duration gamma-ray bursts (GRBs) are powerful probes of the star
formation history of the universe, but the correlation between the two
depends on the highly debated presence and strength of a metallicity
bias. To investigate this correlation, we use a phenomenological model
that successfully describes star formation rates, luminosities, and
stellar masses of star-forming galaxies and apply it to GRB
production. We predict the luminosities, stellar masses, and
metallicities of host galaxies depending on the presence (or absence)
of a metallicity bias. Our best-fitting model includes a moderate
metallicity bias, broadly consistent with the large majority of the
long-duration GRBs in metal-poor environments originating from a
collapsar (probability ∼83%, with [0.74;0.91] range at 90% confidence
level), but with a secondary contribution (∼17%) from a
metal-independent production channel, such as binary evolution.
Because of the mass-metallicity relation of galaxies, the maximum
likelihood model predicts that the metal-independent channel becomes
dominant at z~<2, where hosts have higher metallicities and collapsars
are suppressed. This possibly explains why some studies find no clear
evidence of a metal bias based on low-z samples. However, while
metallicity predictions match observations well at high redshift
(z≳2), there is tension with low-redshift observations, since a
significant fraction of GRB hosts are predicted to have (near) solar
metallicity. This is in contrast to observations, unless obscured,
metal-rich hosts are preferentially missed in current data sets, and
suggests that lower efficiencies of the metal-independent GRB channel
might be preferred following a comprehensive fit that includes
metallicity of GRB hosts from complete samples. Overall, we are able
to clearly establish the presence of a metallicity bias for GRB
production, but continued characterization of GRB host galaxies is
needed to quantify its strength.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 106 46836 Model predictions for GRB host properties
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See also:
J/ApJ/778/128 : GRB-host galaxies photometry (Perley+, 2013)
J/A+A/556/A55 : Multi-color photometry of star-forming galaxies (Ilbert+, 2013)
J/ApJ/683/321 : Metallicities of GRB, DLA, and Lyα galaxies (Fynbo+, 208)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 E12.6 --- z [0.25/9] Model redshift
14- 25 E12.6 --- p [1e-11/10000] Model plateau value (1)
27- 39 E13.6 mag Mag.d [-25.8/-10.9] GRB host galaxy absolute UV
magnitude, including dust extinction (AB scale)
41- 53 E13.6 mag Mag [-28/-11] GRB intrinsic host galaxy absolute UV
magnitude MUV (AB scale)
55- 66 E12.6 Msun M* [181894/4.5662e+11] GRB host galaxy stellar mass
68- 79 E12.6 Msun Mdm GRB host galaxy dark-matter halo mass
81- 93 E13.6 [Sun] logZ [-4.8/0.4] Log Metallicity log10(Z/Z☉)
95-106 E12.6 --- N Cumulative number of GRBs in hosts having
magnitude≤MUV (1)
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Note (1): The normalization for the cumulative distribution is such that
for a given value of p (value for the efficiency of forming GRBs), the
z=3.75 model has cumulative number of GRBs defined as unity for
MAB=-11.0. Other redshift values use the same normalization, so for
example it is immediate to derive the comoving GRB rate at redshift z
relative to redshift z=3.75, at fixed p, since it is simply column 8
of the last line of each group.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Jul-2015