Issue |
A&A
Volume 522, November 2010
|
|
---|---|---|
Article Number | A20 | |
Number of page(s) | 8 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201014801 | |
Published online | 27 October 2010 |
The afterglow and host galaxy of GRB 090205: evidence of a Ly-α emitter at z = 4.65⋆
1
INAF-Osservatorio Astronomico di Brera, via Bianchi 46
23807
Merate
Italy
e-mail: paolo.davanzo@brera.inaf.it
2
ASI Science Data Center, via Galileo Galilei,
00044
Frascati,
Italy
3
Università degli Studi dell’Insubria, Dipartimento di Fisica e
Matematica, via Valleggio
11, 22100
Como,
Italy
4
Università degli Studi di Milano-Bicocca, Dipartimento di
Fisica, piazza delle Scienze
3, 20126
Milano,
Italy
5
Department of Astronomy and Astrophysics, Pensylvania State
University, 525 Davey
Lab, University
Park, PA
16802,
USA
6 Center for Particle Astrophysics, Pensylvania State
University, USA
7
Purple Mountain Observatory, Chinese Academy of Sciences,
Nanjing
210008, PR
China
8
Instituto de Física de Cantabria (CSIC-UC),
39005
Santander,
Spain
9 The George Washington University, Washington, D.C., 20052,
USA
10
NASA/Goddard Space Flight Center, Greenbelt, MD
20771,
USA
11 Department of Physics, Pensylvania State University, USA
12
Department of Physics and Astronomy, University of
Nevada, Las Vegas,
NV
89154,
USA
13
INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00040
Monteporzio Catone, Roma, Italy
14
INAF-Osservatorio Astronomico di Capodimonte, salita Moiariello
16, 80131
Napoli,
Italy
15
International Center for Relativistic Astrophysics, piazza della
Repubblica 10, 65122
Pescara,
Italy
Received:
15
April
2010
Accepted:
28
May
2010
Context. Gamma-ray bursts (GRBs) have proven to be detectable to distances much larger than any other astrophysical object, providing the most effective way, complementing ordinary surveys of studying the high redshift universe.
Aims. We present the results of an observational campaign devoted to the study of the high-z GRB 090205.
Methods. We carried out optical/NIR spectroscopy and imaging of GRB 090205 with the ESO-VLT starting from hours after the event to several days later to detect the host galaxy. We compared the results obtained from our optical/NIR observations with the available Swift high-energy data of this burst.
Results. Our observational campaign led to the detection of the optical afterglow and host galaxy of GRB 090205 and to the first measure of its redshift, z = 4.65. As in other high-z GRBs, GRB 090205 has a short duration in the rest frame with T90,rf = 1.6 s, which suggests that it might belong to the short GRB class. The X-ray afterglow of GRB 090205 has a complex and interesting behavior with a possible rebrightening at 500–1000 s from the trigger time and late flaring activity. Photometric observations of the GRB 090205 host galaxy imply that it is a starburst galaxy with a stellar population younger than ~150 Myr. Moreover, the metallicity of Z > 0.27Z⊙ derived from the GRB afterglow spectrum is among the highest derived from GRB afterglow measurement at high-z, suggesting that the burst occurred in a rather enriched environment. Finally, a detailed analysis of the afterglow spectrum shows the existence of a line corresponding to Lyman-α emission at the redshift of the burst. GRB 090205 is thus hosted by a typical Lyman-α emitter (LAE) at z = 4.65. This makes the host galaxy of GRB 090205 the farthest GRB host galaxy, spectroscopically confirmed, detected to date.
Key words: gamma rays: general
© ESO, 2010
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