TY - JOUR
T1 - Real or interloper? the redshift likelihoods of z > 8 galaxies in the HUDF12
AU - Pirzkal, Nor
AU - Rothberg, Barry
AU - Ryan, Russell
AU - Coe, Dan
AU - Malhotra, Sangeeta
AU - Rhoads, James
AU - Noeske, Kai
PY - 2013/9/20
Y1 - 2013/9/20
N2 - In the absence of spectra, the technique of fitting model galaxy template spectra to observed photometric fluxes has become the workhorse method for determining the redshifts and other properties for high-z galaxy candidates. In this paper, we present an analysis of the most recent and possibly most distant galaxies (z 8-12) discovered in the Hubble Ultra Deep Field (HUDF) using a more robust method of redshift estimation based on Markov Chain Monte Carlo (MCMC) fitting, in contrast to the "best fit" models obtained using simpler χ2 minimization techniques. The advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift for each object as well as any input model parameters. This makes it possible to derive accurate, credible intervals by properly marginalizing over all other input model parameters. We apply our method to 13 recently identified sources in the HUDF and show that, despite claims based on χ2 minimization, none of these sources can be securely ruled out as low redshift interlopers (z < 4) due to the low signal-to-noise of currently available observations. There is an average probability of 21% that these sources are low redshift interlopers.
AB - In the absence of spectra, the technique of fitting model galaxy template spectra to observed photometric fluxes has become the workhorse method for determining the redshifts and other properties for high-z galaxy candidates. In this paper, we present an analysis of the most recent and possibly most distant galaxies (z 8-12) discovered in the Hubble Ultra Deep Field (HUDF) using a more robust method of redshift estimation based on Markov Chain Monte Carlo (MCMC) fitting, in contrast to the "best fit" models obtained using simpler χ2 minimization techniques. The advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift for each object as well as any input model parameters. This makes it possible to derive accurate, credible intervals by properly marginalizing over all other input model parameters. We apply our method to 13 recently identified sources in the HUDF and show that, despite claims based on χ2 minimization, none of these sources can be securely ruled out as low redshift interlopers (z < 4) due to the low signal-to-noise of currently available observations. There is an average probability of 21% that these sources are low redshift interlopers.
KW - galaxies: high-redshift
KW - galaxies: photometry
KW - galaxies: stellar content
KW - methods: statistical
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U2 - 10.1088/0004-637X/775/1/11
DO - 10.1088/0004-637X/775/1/11
M3 - Article
AN - SCOPUS:84883887227
SN - 0004-637X
VL - 775
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 11
ER -