Please use this identifier to cite or link to this item: http://hdl.handle.net/2307/288
Title: Mid-infrared spectroscopy of infrared-luminous galaxies at z similar to 0.5-3
Authors: Hernan-Caballero, Antonio
Perez-Fournon, Ismael
Hatziminaoglou, Evanthia
Afonso-Luis, Alejandro
Rowan-Robinson, Michael
Rigopoulou, Dimitra
Farrah, Duncan
Lonsdale, Colin J.
Babbedge, Thomas
Clements, Dave
Serjeant, Stephen
Pozzi, Francesca
Vaccari, Mattia
Montenegro-Montes, Francisco Miguel
Valtchanov, Ivan
Gonzalez-Solares, Eduardo
Oliver, Seb
Shupe, David
Gruppioni, Carlotta
Vila-Vilaró, Baltazar
Lari, Carlo
La Franca, Fabio
Keywords: ACTIVE GALACTIC NUCLEI
SPECTRAL ENERGY-DISTRIBUTIONS
SPITZER-SPACE-TELESCOPE
POLYCYCLIC AROMATIC-HYDROCARBONS
AREA ISO
SURVEY
ULTRALUMINOUS IRAS GALAXIES
DIFFUSE INTERSTELLAR-MEDIUM
PALOMAR-GREEN QUASARS
STAR-FORMING GALAXIES
DIGITAL SKY SURVEY
Issue Date: 23-Apr-2009
Publisher: Wiley-Blackwell
Abstract: We present results on low-resolution mid-infrared (MIR) spectra of 70IR-luminous galaxies obtained with the infrared spectrograph (IRS)onboard Spitzer. We selected sources from the European Large AreaInfrared Survey with S-15 > 0.8 mJy and photometric or spectroscopic z> 1. About half of the samples are quasi-stellar objects (QSOs) in theoptical, while the remaining sources are galaxies, comprising bothobscured active galactic nuclei (AGN) and starbursts. Redshifts wereobtained from optical spectroscopy, photometric redshifts and the IRSspectra. The later turn out to be reliable for obscured and/orstar-forming sources, thus becoming an ideal complement to opticalspectroscopy for redshift estimation. We estimate monochromatic luminosities at several rest-framewavelengths, equivalent widths and luminosities for the polycyclicaromatic hydrocarbon (PAH) features, and strength of the silicatefeature in individual spectra. We also estimate integrated 8-1000 mu mIR luminosities via spectral energy distribution fitting to MIR andfar-IR (FIR) photometry from the Spitzer Wide-Area InfraredExtragalactic survey and the MIR spectrum. Based on these measurements,we classify the spectra using well-known IR diagnostics, as well as anew one that we propose, into three types of source: those dominated byan unobscured AGN, mostly corresponding to optical quasars (QSOs),those dominated by an obscured AGN and starburst-dominated sources.Starbursts concentrate at z similar to 0.6-1.0 favoured by the shift ofthe 7.7-mu m PAH band into the selection 15-mu m band, while AGN spreadover the 0.5 < z < 3.1 range.Star formation rates (SFR) are estimated for individual sources fromthe luminosity of the PAH features. An estimate of the average PAHluminosity in QSOs and obscured AGN is obtained from the compositespectrum of all sources with reliable redshifts. The estimated mean SFRin the QSOs is 50-100M(circle dot) yr(-1), but the implied FIRluminosity is 3-10 times lower than that obtained from stackinganalysis of the FIR photometry, suggesting destruction of the PAHcarriers by energetic photons from the AGN. The SFR estimated inobscured AGN is two to three times higher than in QSOs of similar MIRluminosity. This discrepancy might not be due to luminosity effects orselection bias alone, but could instead indicate a connection betweenobscuration and star formation. However, the observed correlationbetween silicate absorption and the slope of the NIR to MIR spectrum iscompatible with the obscuration of the AGN emission in these sourcesbeing produced in a dust torus.
URI: http://hdl.handle.net/2307/288
ISSN: 0035-8711
DOI: 10.1111/j.1365-2966.2009.14660.x
Appears in Collections:A - Articolo su rivista
X_Dipartimento di Fisica 'Edoardo Amaldi'

Files in This Item:
File Description SizeFormat Existing users please Login
09MNRAS395_1695.pdfsolo archivio2.05 MBAdobe PDF    Request a copy
SFX Query Show full item record Recommend this item

Page view(s)

1
checked on Aug 4, 2020

Google ScholarTM

Check

Altmetric

Altmetric


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.