Evidence for a massive poststarburst galaxy at z ∼ 6.5

B. Mobasher, M. Dickinson, H. C. Ferguson, M. Giavalisco, T. Wiklind, Daniel P Stark, R. S. Ellis, S. M. Fall, N. A. Grogin, L. A. Moustakas, N. Panagia, M. Sosey, M. Sitavelli, E. Bergeron, S. Casertano, P. Ingraham, A. Koekemoer, I. Labbé, M. Livio, B. RodgersC. Scarlata, J. Vernet, A. Renzini, P. Rosati, H. Küntschner, M. Kümmel, J. R. Walsh, R. Chary, P. Eisenhardt, N. Pirzkal, D. Stern

Research output: Contribution to journalArticle

115 Citations (Scopus)

Abstract

We describe results from a search for high-redshift J-band "dropout" galaxies in the portion of the Great Observatories Origins Deep Survey (GOODS) southern field that is covered by extremely deep imaging from the Hubble Ultradeep Field (HUDF). Using observations at optical, near-infrared, and mid-infrared wavelengths from the Hubble and Spitzer Space Telescopes and the European Southern Observatory Very Large Telescope, we find one particularly remarkable candidate, which we designate HUDF-JD2. Its spectral energy distribution has distinctive features that are consistent with those of a galaxy at z ∼ 6.5, observed several hundred million years after a powerful burst of star formation that produced a stellar mass of 6 × 1011 M. (for a Salpeter IMF). We interpret a prominent photometric break between the near-infrared and Spitzer bandpasses as the 3646 Å Balmer discontinuity. The bestfitting models have low reddening and ages of several hundred Myr, placing the formation of the bulk of the stars at z > 9. Alternative models of dusty galaxies at z ≈ 2.5 are possible, but provide significantly poorer fits to the photometric data. The object is detected with Spitzer at 24 μm. We consider interpretations of the 24 μm emission as originating either from an obscured active nucleus or from star formation and find that the 24 pm detection does not help to uniquely discriminate between the z = 6.5 and 2.5 alternatives. We present optical and near-infrared spectroscopy that has, thus far, failed to detect any spectral features. This nondetection helps limit the solution in which the galaxy is a starburst or active galaxy at z ≈ 2.5, but does not rule it out. If the high-redshift interpretation is correct, HUDF-JD2 is an example of a galaxy that formed by a process strongly resembling traditional models of monolithic collapse, in which a very large mass of stars formed within a remarkably short period of time, at very high redshift.

Original languageEnglish (US)
Pages (from-to)832-844
Number of pages13
JournalAstrophysical Journal
Volume635
Issue number2 I
DOIs
StatePublished - Dec 20 2005
Externally publishedYes

Fingerprint

near infrared
galaxies
observatory
IMF
star formation
infrared spectroscopy
discontinuity
dropouts
stars
active galaxies
Space Infrared Telescope Facility
starburst galaxies
wavelength
spectral energy distribution
European Southern Observatory
stellar mass
Hubble Space Telescope
bursts
observatories
energy

Keywords

  • Cosmology: observations
  • Galaxies: formation
  • Galaxies: high-redshift
  • Galaxies: photometry

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Mobasher, B., Dickinson, M., Ferguson, H. C., Giavalisco, M., Wiklind, T., Stark, D. P., ... Stern, D. (2005). Evidence for a massive poststarburst galaxy at z ∼ 6.5. Astrophysical Journal, 635(2 I), 832-844. https://doi.org/10.1086/497626

Evidence for a massive poststarburst galaxy at z ∼ 6.5. / Mobasher, B.; Dickinson, M.; Ferguson, H. C.; Giavalisco, M.; Wiklind, T.; Stark, Daniel P; Ellis, R. S.; Fall, S. M.; Grogin, N. A.; Moustakas, L. A.; Panagia, N.; Sosey, M.; Sitavelli, M.; Bergeron, E.; Casertano, S.; Ingraham, P.; Koekemoer, A.; Labbé, I.; Livio, M.; Rodgers, B.; Scarlata, C.; Vernet, J.; Renzini, A.; Rosati, P.; Küntschner, H.; Kümmel, M.; Walsh, J. R.; Chary, R.; Eisenhardt, P.; Pirzkal, N.; Stern, D.

In: Astrophysical Journal, Vol. 635, No. 2 I, 20.12.2005, p. 832-844.

Research output: Contribution to journalArticle

Mobasher, B, Dickinson, M, Ferguson, HC, Giavalisco, M, Wiklind, T, Stark, DP, Ellis, RS, Fall, SM, Grogin, NA, Moustakas, LA, Panagia, N, Sosey, M, Sitavelli, M, Bergeron, E, Casertano, S, Ingraham, P, Koekemoer, A, Labbé, I, Livio, M, Rodgers, B, Scarlata, C, Vernet, J, Renzini, A, Rosati, P, Küntschner, H, Kümmel, M, Walsh, JR, Chary, R, Eisenhardt, P, Pirzkal, N & Stern, D 2005, 'Evidence for a massive poststarburst galaxy at z ∼ 6.5', Astrophysical Journal, vol. 635, no. 2 I, pp. 832-844. https://doi.org/10.1086/497626
Mobasher B, Dickinson M, Ferguson HC, Giavalisco M, Wiklind T, Stark DP et al. Evidence for a massive poststarburst galaxy at z ∼ 6.5. Astrophysical Journal. 2005 Dec 20;635(2 I):832-844. https://doi.org/10.1086/497626
Mobasher, B. ; Dickinson, M. ; Ferguson, H. C. ; Giavalisco, M. ; Wiklind, T. ; Stark, Daniel P ; Ellis, R. S. ; Fall, S. M. ; Grogin, N. A. ; Moustakas, L. A. ; Panagia, N. ; Sosey, M. ; Sitavelli, M. ; Bergeron, E. ; Casertano, S. ; Ingraham, P. ; Koekemoer, A. ; Labbé, I. ; Livio, M. ; Rodgers, B. ; Scarlata, C. ; Vernet, J. ; Renzini, A. ; Rosati, P. ; Küntschner, H. ; Kümmel, M. ; Walsh, J. R. ; Chary, R. ; Eisenhardt, P. ; Pirzkal, N. ; Stern, D. / Evidence for a massive poststarburst galaxy at z ∼ 6.5. In: Astrophysical Journal. 2005 ; Vol. 635, No. 2 I. pp. 832-844.
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T1 - Evidence for a massive poststarburst galaxy at z ∼ 6.5

AU - Mobasher, B.

AU - Dickinson, M.

AU - Ferguson, H. C.

AU - Giavalisco, M.

AU - Wiklind, T.

AU - Stark, Daniel P

AU - Ellis, R. S.

AU - Fall, S. M.

AU - Grogin, N. A.

AU - Moustakas, L. A.

AU - Panagia, N.

AU - Sosey, M.

AU - Sitavelli, M.

AU - Bergeron, E.

AU - Casertano, S.

AU - Ingraham, P.

AU - Koekemoer, A.

AU - Labbé, I.

AU - Livio, M.

AU - Rodgers, B.

AU - Scarlata, C.

AU - Vernet, J.

AU - Renzini, A.

AU - Rosati, P.

AU - Küntschner, H.

AU - Kümmel, M.

AU - Walsh, J. R.

AU - Chary, R.

AU - Eisenhardt, P.

AU - Pirzkal, N.

AU - Stern, D.

PY - 2005/12/20

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N2 - We describe results from a search for high-redshift J-band "dropout" galaxies in the portion of the Great Observatories Origins Deep Survey (GOODS) southern field that is covered by extremely deep imaging from the Hubble Ultradeep Field (HUDF). Using observations at optical, near-infrared, and mid-infrared wavelengths from the Hubble and Spitzer Space Telescopes and the European Southern Observatory Very Large Telescope, we find one particularly remarkable candidate, which we designate HUDF-JD2. Its spectral energy distribution has distinctive features that are consistent with those of a galaxy at z ∼ 6.5, observed several hundred million years after a powerful burst of star formation that produced a stellar mass of 6 × 1011 M⊙. (for a Salpeter IMF). We interpret a prominent photometric break between the near-infrared and Spitzer bandpasses as the 3646 Å Balmer discontinuity. The bestfitting models have low reddening and ages of several hundred Myr, placing the formation of the bulk of the stars at z > 9. Alternative models of dusty galaxies at z ≈ 2.5 are possible, but provide significantly poorer fits to the photometric data. The object is detected with Spitzer at 24 μm. We consider interpretations of the 24 μm emission as originating either from an obscured active nucleus or from star formation and find that the 24 pm detection does not help to uniquely discriminate between the z = 6.5 and 2.5 alternatives. We present optical and near-infrared spectroscopy that has, thus far, failed to detect any spectral features. This nondetection helps limit the solution in which the galaxy is a starburst or active galaxy at z ≈ 2.5, but does not rule it out. If the high-redshift interpretation is correct, HUDF-JD2 is an example of a galaxy that formed by a process strongly resembling traditional models of monolithic collapse, in which a very large mass of stars formed within a remarkably short period of time, at very high redshift.

AB - We describe results from a search for high-redshift J-band "dropout" galaxies in the portion of the Great Observatories Origins Deep Survey (GOODS) southern field that is covered by extremely deep imaging from the Hubble Ultradeep Field (HUDF). Using observations at optical, near-infrared, and mid-infrared wavelengths from the Hubble and Spitzer Space Telescopes and the European Southern Observatory Very Large Telescope, we find one particularly remarkable candidate, which we designate HUDF-JD2. Its spectral energy distribution has distinctive features that are consistent with those of a galaxy at z ∼ 6.5, observed several hundred million years after a powerful burst of star formation that produced a stellar mass of 6 × 1011 M⊙. (for a Salpeter IMF). We interpret a prominent photometric break between the near-infrared and Spitzer bandpasses as the 3646 Å Balmer discontinuity. The bestfitting models have low reddening and ages of several hundred Myr, placing the formation of the bulk of the stars at z > 9. Alternative models of dusty galaxies at z ≈ 2.5 are possible, but provide significantly poorer fits to the photometric data. The object is detected with Spitzer at 24 μm. We consider interpretations of the 24 μm emission as originating either from an obscured active nucleus or from star formation and find that the 24 pm detection does not help to uniquely discriminate between the z = 6.5 and 2.5 alternatives. We present optical and near-infrared spectroscopy that has, thus far, failed to detect any spectral features. This nondetection helps limit the solution in which the galaxy is a starburst or active galaxy at z ≈ 2.5, but does not rule it out. If the high-redshift interpretation is correct, HUDF-JD2 is an example of a galaxy that formed by a process strongly resembling traditional models of monolithic collapse, in which a very large mass of stars formed within a remarkably short period of time, at very high redshift.

KW - Cosmology: observations

KW - Galaxies: formation

KW - Galaxies: high-redshift

KW - Galaxies: photometry

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