Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36

T. Krühler; C. Ledoux; J.~P.~U. Fynbo; P.~M. Vreeswijk; S. Schmidl; D. Malesani; Lise Bech Christensen; A. De Cia; J. Hjorth; P. Jakobsson; D.~A. Kann; L. Kaper; S.~D. Vergani; P.~M.~J. Afonso; S. Covino; A. de Ugarte Postigo; V. D'Elia; R. Filgas; P. Goldoni; J. Greiner; O.~E. Hartoog; B. Milvang-Jensen; M. Nardini; S. Piranomonte; A. Rossi; R. Sánchez-Ramírez; P. Schady; S. Schulze; V. Sudilovsky; N.~R. Tanvir; G. Tagliaferri; D.~J. Watson; K. Wiersema; R.~A.~M.~J. Wijers; D. Xu; Georgios Leloudas

doi:10.1051/0004-6361/201321772

Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36

T. Krühler, C. Ledoux, J.~P.~U. Fynbo, P.~M. Vreeswijk, S. Schmidl, D. Malesani, Lise Bech Christensen, A. De Cia, J. Hjorth, P. Jakobsson, D.~A. Kann, L. Kaper, S.~D. Vergani, P.~M.~J. Afonso, S. Covino, A. de Ugarte Postigo, V. D'Elia, R. Filgas, P. Goldoni, J. GreinerO.~E. Hartoog, B. Milvang-Jensen, M. Nardini, S. Piranomonte, A. Rossi, R. Sánchez-Ramírez, P. Schady, S. Schulze, V. Sudilovsky, N.~R. Tanvir, G. Tagliaferri, D.~J. Watson, K. Wiersema, R.~A.~M.~J. Wijers, D. Xu, Georgios Leloudas

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Abstract

We present the discovery of molecular hydrogen (H₂), including the presence of vibrationally-excited H₂ in the optical spectrum of the afterglow of GRB 120815A at z = 2:36 obtained with X-shooter at the VLT. Simultaneous photometric broad-band data from GROND and X-ray observations by Swift/XRT place further constraints on the amount and nature of dust along the sightline. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(Hi)=cm^-2) = 21:95 ± 0:10, prominent H ₂ absorption in the Lyman-Werner bands (log(N(H₂)=cm ^-2) = 20:54 ± 0:13) and thus a molecular gas fraction log f (H₂) = -1:14 ± 0:15. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling of fine-structure and meta-stable transitions of Fe ii and Ni ii to d = 0:5 ± 0:1 kpc. The DLA metallicity ([Zn=H] = -1:15 ± 0:12), visual extinction (A_V 0:15 mag) and dust depletion ([Zn=Fe] = 1:01 ± 0:10) are intermediate between the values of well-studied, H₂- deficient GRB-DLAs observed at high spectral resolution, and the approximately solar metallicity, highly-obscured and H₂-rich GRB 080607 sightline. With respect to N(Hi), metallicity, as well as dust-extinction and depletion, GRB 120815A is fairly representative of the average properties of GRB-DLAs. This demonstrates that molecular hydrogen is present in at least a fraction of the more typical GRBDLAs, and H₂ and H₂ are probably more wide-spread among GRB-selected systems than the few examples of previous detections would suggest. Because H₂ transitions are located redwards of the Lyman α absorption, H₂ opens a second route for positive searches for molecular absorption also in GRB afterglows at lower redshifts and observed at lower spectral resolution. Further detections of molecular gas in GRB-DLAs would allow statistical studies, and, coupled with host follow-up and sub-mm spectroscopy, provide unprecedented insights into the process and conditions of star-formation at high redshift.

Original language	English
Article number	A18
Journal	Astronomy & Astrophysics
Volume	557
ISSN	0004-6361
DOIs	https://doi.org/10.1051/0004-6361/201321772
Publication status	Published - 1 Sept 2013

Keywords

galaxies: ISM, gamma-ray burst: individual: GRB 120815A, galaxies: high-redshift, ISM: molecules, dust, extinction

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10.1051/0004-6361/201321772

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Krühler, T., Ledoux, C., Fynbo, J. P. U., Vreeswijk, P. M., Schmidl, S., Malesani, D., Christensen, L. B., De Cia, A., Hjorth, J., Jakobsson, P., Kann, D. A., Kaper, L., Vergani, S. D., Afonso, P. M. J., Covino, S., de Ugarte Postigo, A., D'Elia, V., Filgas, R., Goldoni, P., ... Leloudas, G. (2013). Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36. Astronomy & Astrophysics, 557, [A18]. https://doi.org/10.1051/0004-6361/201321772

Krühler, T, Ledoux, C, Fynbo, JPU, Vreeswijk, PM, Schmidl, S, Malesani, D , Christensen, LB, De Cia, A, Hjorth, J, Jakobsson, P, Kann, DA, Kaper, L, Vergani, SD, Afonso, PMJ, Covino, S, de Ugarte Postigo, A, D'Elia, V, Filgas, R, Goldoni, P, Greiner, J, Hartoog, OE, Milvang-Jensen, B, Nardini, M, Piranomonte, S, Rossi, A, Sánchez-Ramírez, R, Schady, P, Schulze, S, Sudilovsky, V, Tanvir, NR, Tagliaferri, G, Watson, DJ, Wiersema, K, Wijers, RAMJ, Xu, D & Leloudas, G 2013, 'Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36', Astronomy & Astrophysics, vol. 557, A18. https://doi.org/10.1051/0004-6361/201321772

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title = "Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36",

abstract = "We present the discovery of molecular hydrogen (H2), including the presence of vibrationally-excited H2 in the optical spectrum of the afterglow of GRB 120815A at z = 2:36 obtained with X-shooter at the VLT. Simultaneous photometric broad-band data from GROND and X-ray observations by Swift/XRT place further constraints on the amount and nature of dust along the sightline. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(Hi)=cm-2) = 21:95 ± 0:10, prominent H 2 absorption in the Lyman-Werner bands (log(N(H2)=cm -2) = 20:54 ± 0:13) and thus a molecular gas fraction log f (H2) = -1:14 ± 0:15. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling of fine-structure and meta-stable transitions of Fe ii and Ni ii to d = 0:5 ± 0:1 kpc. The DLA metallicity ([Zn=H] = -1:15 ± 0:12), visual extinction (AV 0:15 mag) and dust depletion ([Zn=Fe] = 1:01 ± 0:10) are intermediate between the values of well-studied, H2- deficient GRB-DLAs observed at high spectral resolution, and the approximately solar metallicity, highly-obscured and H2-rich GRB 080607 sightline. With respect to N(Hi), metallicity, as well as dust-extinction and depletion, GRB 120815A is fairly representative of the average properties of GRB-DLAs. This demonstrates that molecular hydrogen is present in at least a fraction of the more typical GRBDLAs, and H2 and H2 are probably more wide-spread among GRB-selected systems than the few examples of previous detections would suggest. Because H2 transitions are located redwards of the Lyman α absorption, H2 opens a second route for positive searches for molecular absorption also in GRB afterglows at lower redshifts and observed at lower spectral resolution. Further detections of molecular gas in GRB-DLAs would allow statistical studies, and, coupled with host follow-up and sub-mm spectroscopy, provide unprecedented insights into the process and conditions of star-formation at high redshift.",

keywords = "galaxies: ISM, gamma-ray burst: individual: GRB 120815A, galaxies: high-redshift, ISM: molecules, dust, extinction",

author = "T. Kr{\"u}hler and C. Ledoux and J.~P.~U. Fynbo and P.~M. Vreeswijk and S. Schmidl and D. Malesani and Christensen, {Lise Bech} and {De Cia}, A. and J. Hjorth and P. Jakobsson and D.~A. Kann and L. Kaper and S.~D. Vergani and P.~M.~J. Afonso and S. Covino and {de Ugarte Postigo}, A. and V. D'Elia and R. Filgas and P. Goldoni and J. Greiner and O.~E. Hartoog and B. Milvang-Jensen and M. Nardini and S. Piranomonte and A. Rossi and R. S{\'a}nchez-Ram{\'i}rez and P. Schady and S. Schulze and V. Sudilovsky and N.~R. Tanvir and G. Tagliaferri and D.~J. Watson and K. Wiersema and R.~A.~M.~J. Wijers and D. Xu and Georgios Leloudas",

year = "2013",

month = sep,

day = "1",

doi = "10.1051/0004-6361/201321772",

language = "English",

volume = "557",

journal = "Astronomy and Astrophysics Supplement Series",

issn = "0004-6361",

publisher = "E D P Sciences",

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TY - JOUR

T1 - Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36

AU - Krühler, T.

AU - Ledoux, C.

AU - Fynbo, J.~P.~U.

AU - Vreeswijk, P.~M.

AU - Schmidl, S.

AU - Malesani, D.

AU - Christensen, Lise Bech

AU - De Cia, A.

AU - Hjorth, J.

AU - Jakobsson, P.

AU - Kann, D.~A.

AU - Kaper, L.

AU - Vergani, S.~D.

AU - Afonso, P.~M.~J.

AU - Covino, S.

AU - de Ugarte Postigo, A.

AU - D'Elia, V.

AU - Filgas, R.

AU - Goldoni, P.

AU - Greiner, J.

AU - Hartoog, O.~E.

AU - Milvang-Jensen, B.

AU - Nardini, M.

AU - Piranomonte, S.

AU - Rossi, A.

AU - Sánchez-Ramírez, R.

AU - Schady, P.

AU - Schulze, S.

AU - Sudilovsky, V.

AU - Tanvir, N.~R.

AU - Tagliaferri, G.

AU - Watson, D.~J.

AU - Wiersema, K.

AU - Wijers, R.~A.~M.~J.

AU - Xu, D.

AU - Leloudas, Georgios

PY - 2013/9/1

Y1 - 2013/9/1

N2 - We present the discovery of molecular hydrogen (H2), including the presence of vibrationally-excited H2 in the optical spectrum of the afterglow of GRB 120815A at z = 2:36 obtained with X-shooter at the VLT. Simultaneous photometric broad-band data from GROND and X-ray observations by Swift/XRT place further constraints on the amount and nature of dust along the sightline. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(Hi)=cm-2) = 21:95 ± 0:10, prominent H 2 absorption in the Lyman-Werner bands (log(N(H2)=cm -2) = 20:54 ± 0:13) and thus a molecular gas fraction log f (H2) = -1:14 ± 0:15. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling of fine-structure and meta-stable transitions of Fe ii and Ni ii to d = 0:5 ± 0:1 kpc. The DLA metallicity ([Zn=H] = -1:15 ± 0:12), visual extinction (AV 0:15 mag) and dust depletion ([Zn=Fe] = 1:01 ± 0:10) are intermediate between the values of well-studied, H2- deficient GRB-DLAs observed at high spectral resolution, and the approximately solar metallicity, highly-obscured and H2-rich GRB 080607 sightline. With respect to N(Hi), metallicity, as well as dust-extinction and depletion, GRB 120815A is fairly representative of the average properties of GRB-DLAs. This demonstrates that molecular hydrogen is present in at least a fraction of the more typical GRBDLAs, and H2 and H2 are probably more wide-spread among GRB-selected systems than the few examples of previous detections would suggest. Because H2 transitions are located redwards of the Lyman α absorption, H2 opens a second route for positive searches for molecular absorption also in GRB afterglows at lower redshifts and observed at lower spectral resolution. Further detections of molecular gas in GRB-DLAs would allow statistical studies, and, coupled with host follow-up and sub-mm spectroscopy, provide unprecedented insights into the process and conditions of star-formation at high redshift.

AB - We present the discovery of molecular hydrogen (H2), including the presence of vibrationally-excited H2 in the optical spectrum of the afterglow of GRB 120815A at z = 2:36 obtained with X-shooter at the VLT. Simultaneous photometric broad-band data from GROND and X-ray observations by Swift/XRT place further constraints on the amount and nature of dust along the sightline. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(Hi)=cm-2) = 21:95 ± 0:10, prominent H 2 absorption in the Lyman-Werner bands (log(N(H2)=cm -2) = 20:54 ± 0:13) and thus a molecular gas fraction log f (H2) = -1:14 ± 0:15. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling of fine-structure and meta-stable transitions of Fe ii and Ni ii to d = 0:5 ± 0:1 kpc. The DLA metallicity ([Zn=H] = -1:15 ± 0:12), visual extinction (AV 0:15 mag) and dust depletion ([Zn=Fe] = 1:01 ± 0:10) are intermediate between the values of well-studied, H2- deficient GRB-DLAs observed at high spectral resolution, and the approximately solar metallicity, highly-obscured and H2-rich GRB 080607 sightline. With respect to N(Hi), metallicity, as well as dust-extinction and depletion, GRB 120815A is fairly representative of the average properties of GRB-DLAs. This demonstrates that molecular hydrogen is present in at least a fraction of the more typical GRBDLAs, and H2 and H2 are probably more wide-spread among GRB-selected systems than the few examples of previous detections would suggest. Because H2 transitions are located redwards of the Lyman α absorption, H2 opens a second route for positive searches for molecular absorption also in GRB afterglows at lower redshifts and observed at lower spectral resolution. Further detections of molecular gas in GRB-DLAs would allow statistical studies, and, coupled with host follow-up and sub-mm spectroscopy, provide unprecedented insights into the process and conditions of star-formation at high redshift.

KW - galaxies: ISM, gamma-ray burst: individual: GRB 120815A, galaxies: high-redshift, ISM: molecules, dust, extinction

U2 - 10.1051/0004-6361/201321772

DO - 10.1051/0004-6361/201321772

M3 - Journal article

SN - 0004-6361

VL - 557

JO - Astronomy and Astrophysics Supplement Series

JF - Astronomy and Astrophysics Supplement Series

M1 - A18

ER -

Molecular hydrogen in the damped Lyman alpha system towards GRB 120815A at z=2.36

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Keywords

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