SETI public: Spitzer Detection of PAH and Silicate Dust Features in the Mid-Infrared Spectra

• Previous message: LARRY KLAES: "SETI public: Spitzer Detection of PAH and Silicate Dust Features in the Mid-Infrared Spectra"

Astrophysics, abstract
astro-ph/0504336
From: Lin Yan [view email]
Date: Thu, 14 Apr 2005 23:20:31 GMT (75kb)

Spitzer Detection of PAH and Silicate Dust Features in the Mid-Infrared
Spectra of z~2 Ultraluminous Infrared Galaxies

Authors: Lin Yan (Spitzer Science Center, Caltech), R. Chary, L. Armus, H.
Teplitz, G. Helou, D. Frayer, D. Fadda, J. Surace, P. Choi (Spitzer Science
Center, Caltech)

Comments: 23 pages, Accepted for publication in the Astrophysical Journal

We report the initial results from a Spitzer GO-1 program to obtain low
resolution, mid-infrared spectra of infrared luminous galaxies at z~1-2.
This paper presents the spectra of eight sources observed with the Spitzer
InfraRed Spectrograph (IRS). Of the eight spectra, six have mid-IR spectral
features, either emission from Polycyclic Aromatic Hydrocarbon (PAH) or
silicate absorption. Based on these mid-IR features, the inferred six
redshifts are in the range of 1.8-2.6. The remaining two spectra detect only
strong continua, thus do not yield redshift information. Strong, multiple
PAH emission features are detected in two sources, and weak PAH emission in
another two. These data provide direct evidence that PAH molecules are
present and directly observable in ULIRGs at z~2.
The six sources with measured redshifts are dusty, infrared luminous
galaxies at z~2 with estimated $L_{bol} \sim 10^{13}L_\odot$. Of the eight
sources, two appear starburst dominated; two with only power law continua
are probably type I QSOs; and the remaining four are likely composite
systems containing a buried AGN and a starburst component. Since half of our
sample are optically faint sources with R>25.5mag (Vega), our results
demonstrate the potential of using mid-infrared spectroscopy, especially the
Aromatic and silicate features produced by dust grains to directly probe
optically faint and infrared luminous populations at high redshift.

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http://xxx.lanl.gov/abs/astro-ph/0504336

• Previous message: LARRY KLAES: "SETI public: Spitzer Detection of PAH and Silicate Dust Features in the Mid-Infrared Spectra"

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