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GRB 980425 host: [C II], [O I], and CO lines reveal recent enhancement of star formation due to atomic gas inflow

MJ Michałowski, JM Castro Cerón, JL Wardlow, A Karska, H Messias, P van der Werf, LK Hunt, Maarten Baes UGent, AJ Castro-Tirado, Gianfranco Gentile, et al. (2016) ASTRONOMY & ASTROPHYSICS. 595.
abstract
Context. Accretion of gas from the intergalactic medium is required to fuel star formation in galaxies. We have recently suggested that this process can be studied using host galaxies of gamma-ray bursts (GRBs). Aims. Our aim is to test this possibility by studying in detail the properties of gas in the closest galaxy hosting a GRB (980425). Methods. We obtained the first ever far-infrared (FIR) line observations of a GRB host, namely Herschel/PACS resolved [C II] 158 mu m and [O I] 63 mu m spectroscopy, and an APEX/SHeFI CO(2-1) line detection and ALMA CO(1-0) observations of the GRB980425 host. Results. The GRB980425 host has elevated [CII]/FIR and [O I]/FIR ratios and higher values of star formation rates (SFR) derived from line ([C II], [O I], H alpha) than from continuum (UV, IR, radio) indicators. [C II] emission exhibits a normal morphology, peaking at the galaxy centre, whereas [O I] is concentrated close to the GRB position and the nearby Wolf-Rayet region. The high [O I] flux indicates that there is high radiation field and high gas density at these positions, as derived from modelling of photo-dissociation regions. The [C II]/CO luminosity ratio of the GRB980425 host is close to the highest values found for local star-forming galaxies. Indeed, its CO-derived molecular gas mass is low given its SFR and metallicity, but the [C II]-derived molecular gas mass is close to the expected value. Conclusions. The [O I] and H I concentrations and the high radiation field and density close to the GRB position are consistent with the hypothesis of a very recent (at most a few tens of Myr ago) inflow of atomic gas triggering star formation. In this scenario dust has not had time to build up (explaining high line-to-continuum ratios). Such a recent enhancement of star formation activity would indeed manifest itself in high SFRline/SFRcontinuum ratios because the line indicators are sensitive only to recent (less than or similar to 10 Myr) activity, whereas the continuum indicators measure the SFR averaged over much longer periods (similar to 100 Myr). Within a sample of 32 other GRB hosts, 20 exhibit SFRline/SFRcontinuum > 1 with a mean ratio of 1.74 +/- 0.32. This is consistent with a very recent enhancement of star formation that is common among GRB hosts, so galaxies that have recently experienced inflow of gas may preferentially host stars exploding as GRBs. Therefore GRBs may be used to select a unique sample of galaxies that is suitable for the investigation of recent gas accretion.
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author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
dust, extinction, galaxies: individual: ESO 184-G82, galaxies: ISM, galaxies: star formation, submillimeter: galaxies, gamma-ray burst: individual: 980425, GAMMA-RAY BURST, CO-TO-H-2 CONVERSION FACTOR, VLT/X-SHOOTER SPECTROSCOPY, GALAXY PHYSICAL PARAMETERS, SWIFT/BAT6 COMPLETE SAMPLE, FAR-INFRARED SPECTROSCOPY, LOW-METALLICITY STARBURST, FORMATION RATE INDICATORS, INITIAL MASS FUNCTION, SIMILAR-TO 1
journal title
ASTRONOMY & ASTROPHYSICS
Astron. Astrophys.
volume
595
article number
A72
pages
14 pages
Web of Science type
Article
Web of Science id
000388573500132
JCR category
ASTRONOMY & ASTROPHYSICS
JCR impact factor
5.014 (2016)
JCR rank
10/63 (2016)
JCR quartile
1 (2016)
ISSN
1432-0746
DOI
10.1051/0004-6361/201629441
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
8503055
handle
http://hdl.handle.net/1854/LU-8503055
date created
2017-01-19 16:21:02
date last changed
2017-03-01 11:43:03
@article{8503055,
  abstract     = {Context. Accretion of gas from the intergalactic medium is required to fuel star formation in galaxies. We have recently suggested that this process can be studied using host galaxies of gamma-ray bursts (GRBs). 
Aims. Our aim is to test this possibility by studying in detail the properties of gas in the closest galaxy hosting a GRB (980425). 
Methods. We obtained the first ever far-infrared (FIR) line observations of a GRB host, namely Herschel/PACS resolved [C II] 158 mu m and [O I] 63 mu m spectroscopy, and an APEX/SHeFI CO(2-1) line detection and ALMA CO(1-0) observations of the GRB980425 host. 
Results. The GRB980425 host has elevated [CII]/FIR and [O I]/FIR ratios and higher values of star formation rates (SFR) derived from line ([C II], [O I], H alpha) than from continuum (UV, IR, radio) indicators. [C II] emission exhibits a normal morphology, peaking at the galaxy centre, whereas [O I] is concentrated close to the GRB position and the nearby Wolf-Rayet region. The high [O I] flux indicates that there is high radiation field and high gas density at these positions, as derived from modelling of photo-dissociation regions. The [C II]/CO luminosity ratio of the GRB980425 host is close to the highest values found for local star-forming galaxies. Indeed, its CO-derived molecular gas mass is low given its SFR and metallicity, but the [C II]-derived molecular gas mass is close to the expected value. 
Conclusions. The [O I] and H I concentrations and the high radiation field and density close to the GRB position are consistent with the hypothesis of a very recent (at most a few tens of Myr ago) inflow of atomic gas triggering star formation. In this scenario dust has not had time to build up (explaining high line-to-continuum ratios). Such a recent enhancement of star formation activity would indeed manifest itself in high SFRline/SFRcontinuum ratios because the line indicators are sensitive only to recent (less than or similar to 10 Myr) activity, whereas the continuum indicators measure the SFR averaged over much longer periods (similar to 100 Myr). Within a sample of 32 other GRB hosts, 20 exhibit SFRline/SFRcontinuum {\textrangle} 1 with a mean ratio of 1.74 +/- 0.32. This is consistent with a very recent enhancement of star formation that is common among GRB hosts, so galaxies that have recently experienced inflow of gas may preferentially host stars exploding as GRBs. Therefore GRBs may be used to select a unique sample of galaxies that is suitable for the investigation of recent gas accretion.},
  articleno    = {A72},
  author       = {Micha\unmatched{0142}owski, MJ and Castro Cer{\'o}n, JM and Wardlow, JL and Karska, A and Messias, H and van der Werf, P and Hunt, LK and Baes, Maarten and Castro-Tirado, AJ and Gentile, Gianfranco and Hjorth, J and Le Floc{\textquoteright}h, E and P{\'e}rez-Mart{\'i}nez, R and Nicuesa Guelbenzu, A and Rasmussen, J and Rizzo, JR and Rossi, A and S{\'a}nchez-Portal, M and Schady, P and Sollerman, J and Xu, D},
  issn         = {1432-0746},
  journal      = {ASTRONOMY \& ASTROPHYSICS},
  keyword      = {dust,extinction,galaxies: individual: ESO 184-G82,galaxies: ISM,galaxies: star formation,submillimeter: galaxies,gamma-ray burst: individual: 980425,GAMMA-RAY BURST,CO-TO-H-2 CONVERSION FACTOR,VLT/X-SHOOTER SPECTROSCOPY,GALAXY PHYSICAL PARAMETERS,SWIFT/BAT6 COMPLETE SAMPLE,FAR-INFRARED SPECTROSCOPY,LOW-METALLICITY STARBURST,FORMATION RATE INDICATORS,INITIAL MASS FUNCTION,SIMILAR-TO 1},
  language     = {eng},
  pages        = {14},
  title        = {GRB 980425 host: [C\,II], [O\,I], and CO lines reveal recent enhancement of star formation due to atomic gas inflow},
  url          = {http://dx.doi.org/10.1051/0004-6361/201629441},
  volume       = {595},
  year         = {2016},
}

Chicago
Michałowski, MJ, JM Castro Cerón, JL Wardlow, A Karska, H Messias, P van der Werf, LK Hunt, et al. 2016. “GRB 980425 Host: [C II], [O I], and CO Lines Reveal Recent Enhancement of Star Formation Due to Atomic Gas Inflow.” Astronomy & Astrophysics 595.
APA
Michałowski, M., Castro Cerón, J., Wardlow, J., Karska, A., Messias, H., van der Werf, P., Hunt, L., et al. (2016). GRB 980425 host: [C II], [O I], and CO lines reveal recent enhancement of star formation due to atomic gas inflow. ASTRONOMY & ASTROPHYSICS, 595.
Vancouver
1.
Michałowski M, Castro Cerón J, Wardlow J, Karska A, Messias H, van der Werf P, et al. GRB 980425 host: [C II], [O I], and CO lines reveal recent enhancement of star formation due to atomic gas inflow. ASTRONOMY & ASTROPHYSICS. 2016;595.
MLA
Michałowski, MJ, JM Castro Cerón, JL Wardlow, et al. “GRB 980425 Host: [C II], [O I], and CO Lines Reveal Recent Enhancement of Star Formation Due to Atomic Gas Inflow.” ASTRONOMY & ASTROPHYSICS 595 (2016): n. pag. Print.