---
_id: '17774'
abstract:
- lang: eng
  text: We present grism spectra taken with the Advanced Camera for Surveys (ACS)
    to identify 29 red sources with (i775 - z850) ≥ 0.9 in the Hubble Ultra Deep Field
    (HUDF). Of these, 23 are found to be galaxies at redshifts between z = 5.4 and
    6.7, identified by the break at 1216 Å due to intergalactic medium (IGM) absorption;
    two are late-type dwarf stars with red colors; and four are galaxies with colors
    and spectral shapes similar to dust-reddened or old galaxies at redshifts z ≈
    1-2. This constitutes the largest uniform, flux-limited sample of spectroscopically
    confirmed galaxies at such faint fluxes (z850 ≤ 27.5). Many are also among the
    most distant spectroscopically confirmed galaxies (at redshifts up to z = 6.7).
    We find a significant overdensity of galaxies at redshifts z = 5.9 ± 0.2. Nearly
    two-thirds of the galaxies in our sample (15/23) belong to this peak. Taking into
    account the selection function and the redshift sensitivity of the survey, we
    get a conservative overdensity of at least a factor of 2 along the line of sight.
    The galaxies found in this redshift peak are also localized in the plane of the
    sky in a nonrandom manner, occupying about half of the ACS chip. Thus the volume
    overdensity is a factor of 4. The star formation rate derived from detected sources
    in this overdense region is sufficient to reionize the local IGM.
article_processing_charge: No
article_type: original
author:
- first_name: S.
  full_name: Malhotra, S.
  last_name: Malhotra
- first_name: J. E.
  full_name: Rhoads, J. E.
  last_name: Rhoads
- first_name: N.
  full_name: Pirzkal, N.
  last_name: Pirzkal
- first_name: Zoltán
  full_name: Haiman, Zoltán
  id: 7c006e8c-cc0d-11ee-8322-cb904ef76f36
  last_name: Haiman
- first_name: C.
  full_name: Xu, C.
  last_name: Xu
- first_name: E.
  full_name: Daddi, E.
  last_name: Daddi
- first_name: H.
  full_name: Yan, H.
  last_name: Yan
- first_name: L. E.
  full_name: Bergeron, L. E.
  last_name: Bergeron
- first_name: J.
  full_name: Wang, J.
  last_name: Wang
- first_name: H. C.
  full_name: Ferguson, H. C.
  last_name: Ferguson
- first_name: C.
  full_name: Gronwall, C.
  last_name: Gronwall
- first_name: A.
  full_name: Koekemoer, A.
  last_name: Koekemoer
- first_name: M.
  full_name: Kuemmel, M.
  last_name: Kuemmel
- first_name: L. A.
  full_name: Moustakas, L. A.
  last_name: Moustakas
- first_name: N.
  full_name: Panagia, N.
  last_name: Panagia
- first_name: A.
  full_name: Pasquali, A.
  last_name: Pasquali
- first_name: M.
  full_name: Stiavelli, M.
  last_name: Stiavelli
- first_name: J.
  full_name: Walsh, J.
  last_name: Walsh
- first_name: R. A.
  full_name: Windhorst, R. A.
  last_name: Windhorst
- first_name: S.
  full_name: di Serego Alighieri, S.
  last_name: di Serego Alighieri
citation:
  ama: Malhotra S, Rhoads JE, Pirzkal N, et al. An overdensity of galaxies at z= 5.9
    ± 0.2 in the Hubble Ultra Deep Field confirmed using the ACS grism. <i>The Astrophysical
    Journal</i>. 2005;626(2):666-679. doi:<a href="https://doi.org/10.1086/430047">10.1086/430047</a>
  apa: Malhotra, S., Rhoads, J. E., Pirzkal, N., Haiman, Z., Xu, C., Daddi, E., …
    di Serego Alighieri, S. (2005). An overdensity of galaxies at z= 5.9 ± 0.2 in
    the Hubble Ultra Deep Field confirmed using the ACS grism. <i>The Astrophysical
    Journal</i>. American Astronomical Society. <a href="https://doi.org/10.1086/430047">https://doi.org/10.1086/430047</a>
  chicago: Malhotra, S., J. E. Rhoads, N. Pirzkal, Zoltán Haiman, C. Xu, E. Daddi,
    H. Yan, et al. “An Overdensity of Galaxies at Z= 5.9 ± 0.2 in the Hubble Ultra
    Deep Field Confirmed Using the ACS Grism.” <i>The Astrophysical Journal</i>. American
    Astronomical Society, 2005. <a href="https://doi.org/10.1086/430047">https://doi.org/10.1086/430047</a>.
  ieee: S. Malhotra <i>et al.</i>, “An overdensity of galaxies at z= 5.9 ± 0.2 in
    the Hubble Ultra Deep Field confirmed using the ACS grism,” <i>The Astrophysical
    Journal</i>, vol. 626, no. 2. American Astronomical Society, pp. 666–679, 2005.
  ista: Malhotra S, Rhoads JE, Pirzkal N, Haiman Z, Xu C, Daddi E, Yan H, Bergeron
    LE, Wang J, Ferguson HC, Gronwall C, Koekemoer A, Kuemmel M, Moustakas LA, Panagia
    N, Pasquali A, Stiavelli M, Walsh J, Windhorst RA, di Serego Alighieri S. 2005.
    An overdensity of galaxies at z= 5.9 ± 0.2 in the Hubble Ultra Deep Field confirmed
    using the ACS grism. The Astrophysical Journal. 626(2), 666–679.
  mla: Malhotra, S., et al. “An Overdensity of Galaxies at Z= 5.9 ± 0.2 in the Hubble
    Ultra Deep Field Confirmed Using the ACS Grism.” <i>The Astrophysical Journal</i>,
    vol. 626, no. 2, American Astronomical Society, 2005, pp. 666–79, doi:<a href="https://doi.org/10.1086/430047">10.1086/430047</a>.
  short: S. Malhotra, J.E. Rhoads, N. Pirzkal, Z. Haiman, C. Xu, E. Daddi, H. Yan,
    L.E. Bergeron, J. Wang, H.C. Ferguson, C. Gronwall, A. Koekemoer, M. Kuemmel,
    L.A. Moustakas, N. Panagia, A. Pasquali, M. Stiavelli, J. Walsh, R.A. Windhorst,
    S. di Serego Alighieri, The Astrophysical Journal 626 (2005) 666–679.
date_created: 2024-09-06T10:04:19Z
date_published: 2005-06-20T00:00:00Z
date_updated: 2024-09-30T11:34:11Z
day: '20'
doi: 10.1086/430047
extern: '1'
intvolume: '       626'
issue: '2'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://doi.org/10.1086/430047
month: '06'
oa: 1
oa_version: Published Version
page: 666-679
publication: The Astrophysical Journal
publication_identifier:
  issn:
  - 0004-637X
  - 1538-4357
publication_status: published
publisher: American Astronomical Society
quality_controlled: '1'
scopus_import: '1'
status: public
title: An overdensity of galaxies at z= 5.9 ± 0.2 in the Hubble Ultra Deep Field confirmed
  using the ACS grism
type: journal_article
user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345
volume: 626
year: '2005'
...