TY - JOUR
T1 - A Nearby Gamma-Ray Burst Host Prototype for z ~ 7 Lyman-break Galaxies
T2 - Spitzer-IRS and X-shooter Spectroscopy of the Host Galaxy of GRB 031203
AU - Watson..[et al.], Darach Jafar
AU - French, John Samuel
AU - Hjorth, Jens
AU - Malesani, Daniele
AU - Fynbo, Johan Peter Uldall
AU - Castro Cerón, José María
PY - 2011/11/1
Y1 - 2011/11/1
N2 - Gamma-ray burst (GRB) host galaxies have been studied extensively in optical photometry and spectroscopy. Here we present the first mid-infrared spectrum of a GRB host, HG031203. It is one of the nearest GRB hosts at z = 0.1055, allowing both low- and high-resolution spectroscopy with the Spitzer Infrared Spectrograph (IRS). Medium-resolution UV to K-band spectroscopy with the X-shooter spectrograph on the Very Large Telescope is also presented, along with Spitzer IRAC and MIPS photometry, as well as radio and submillimeter observations. These data allow us to construct a UV to radio spectral energy distribution with almost complete spectroscopic coverage from 0.3 to 35μm of a GRB host galaxy for the first time, potentially valuable as a template for future model comparisons. The IRS spectra show strong, high-ionization fine structure line emission indicative of a hard radiation field in the galaxy - in particular the [S IV]/[S III] and [Ne III]/[Ne II] ratios - suggestive of strong ongoing star formation and a very young stellar population. The absence of any polycyclic aromatic hydrocarbon emission supports these conclusions, as does the probable hot peak dust temperature, making HG031203 similar to the prototypical blue compact dwarf galaxy (BCD), IIZw40. The selection of HG031203 via the presence of a GRB suggests that it might be a useful analog of very young star-forming galaxies in the early universe, and hints that local BCDs may be used as more reliable analogs of star formation in the early universe than typical local starbursts. We look at the current debate on the ages of the dominant stellar populations in z ∼ 7 and z ∼ 8 galaxies in this context. The nebular line emission is so strong in HG031203 that at z ∼ 7, it can reproduce the spectral energy distributions of z-band dropout galaxies with elevated IRAC 3.6 and 4.5 μm fluxes without the need to invoke a 4000 Å break. Indeed, photometry of HG031203 shows elevation of the broadband V-magnitude at a level similar to the IRAC elevation in stacked z-band dropouts, solely due to its strong [O III] line emission.
AB - Gamma-ray burst (GRB) host galaxies have been studied extensively in optical photometry and spectroscopy. Here we present the first mid-infrared spectrum of a GRB host, HG031203. It is one of the nearest GRB hosts at z = 0.1055, allowing both low- and high-resolution spectroscopy with the Spitzer Infrared Spectrograph (IRS). Medium-resolution UV to K-band spectroscopy with the X-shooter spectrograph on the Very Large Telescope is also presented, along with Spitzer IRAC and MIPS photometry, as well as radio and submillimeter observations. These data allow us to construct a UV to radio spectral energy distribution with almost complete spectroscopic coverage from 0.3 to 35μm of a GRB host galaxy for the first time, potentially valuable as a template for future model comparisons. The IRS spectra show strong, high-ionization fine structure line emission indicative of a hard radiation field in the galaxy - in particular the [S IV]/[S III] and [Ne III]/[Ne II] ratios - suggestive of strong ongoing star formation and a very young stellar population. The absence of any polycyclic aromatic hydrocarbon emission supports these conclusions, as does the probable hot peak dust temperature, making HG031203 similar to the prototypical blue compact dwarf galaxy (BCD), IIZw40. The selection of HG031203 via the presence of a GRB suggests that it might be a useful analog of very young star-forming galaxies in the early universe, and hints that local BCDs may be used as more reliable analogs of star formation in the early universe than typical local starbursts. We look at the current debate on the ages of the dominant stellar populations in z ∼ 7 and z ∼ 8 galaxies in this context. The nebular line emission is so strong in HG031203 that at z ∼ 7, it can reproduce the spectral energy distributions of z-band dropout galaxies with elevated IRAC 3.6 and 4.5 μm fluxes without the need to invoke a 4000 Å break. Indeed, photometry of HG031203 shows elevation of the broadband V-magnitude at a level similar to the IRAC elevation in stacked z-band dropouts, solely due to its strong [O III] line emission.
U2 - 10.1088/0004-637X/741/1/58
DO - 10.1088/0004-637X/741/1/58
M3 - Journal article
SN - 0004-637X
VL - 741
SP - 58
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
ER -