An overdensity of galaxies at z=5.9 +/-0.2 in the Ultra Deep Field confirmed using the ACS grism

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dc.creatorMalhotra, S.
dc.creatorRhoads, J. E.
dc.creatorPirzkal, N.
dc.creatorHaiman, Z.
dc.creatorXu, C.
dc.creatorDaddi, E.
dc.creatorYan, H.
dc.creatorBergeron, L. E.
dc.creatorWang, J.
dc.creatorFerguson, H. A.
dc.creatorKoekemoer, A.
dc.creatorMoustakas, L. A.
dc.creatorPanagia, N.
dc.creatorStiavelli, M.
dc.creatorWalsh, J.
dc.creatorWindhorst, R. A.
dc.creatorPasquali, A.
dc.creatorGronwall, C.
dc.creatorKuemmel, M.
dc.creatorAlighieri, S. di Serego
dc.date2005-01-24
dc.date2005-03-02
dc.date.accessioned2026-07-07T11:57:09Z
dc.date.available2026-07-07T11:57:09Z
dc.descriptionWe present grism spectra taken with the Advanced Camera for Surveys to identify 29 red sources with (i'-z') > 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 angstrom due to IGM absorption; two are late type dwarf stars with red colors; and four are galaxies with colors and spectral shape 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 z'<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 two along the line-of-sight. The galaxies found in this redshift peak are also localized in the plane of the sky in a non-random manner, occupying about half of the ACS chip. Thus the volume overdensity is a factor of four. The star-formation rate derived from detected sources in this overdense region is sufficient to reionize the local IGM.
dc.descriptionAccepted for publication in ApJ. Minor changes to text and figures 1 and 4
dc.identifierhttps://arxiv.org/abs/astro-ph/0501478
dc.identifierhttp://arxiv.org/abs/astro-ph/0501478
dc.identifierAstrophys.J.626:666-679,2005
dc.identifierdoi:10.1086/430047
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/205781
dc.subjectAstrophysics
dc.titleAn overdensity of galaxies at z=5.9 +/-0.2 in the Ultra Deep Field confirmed using the ACS grism
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