TY - JOUR
T1 - Local luminous infrared galaxies. I. Spatially resolved observations with the Spitzer infrared spectrograph
AU - Pereira-Santaella, Miguel
AU - Alonso-Herrero, Almudena
AU - Rieke, George H.
AU - Colina, Luis
AU - Díaz-Santos, Tanio
AU - Smith, J. D.T.
AU - Pérez-Gonzlez, Pablo G.
AU - Engelbracht, Charles W.
PY - 2010
Y1 - 2010
N2 - We present results from the Spitzer Infrared Spectrograph spectral mapping observations of 15 local luminous infrared galaxies (LIRGs). In this paper, we investigate the spatial variations of the mid-IR emission which includes fine structure lines, molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum emission, and the 9.7 μm silicate feature. We also compare the nuclear and integrated spectra. We find that the star formation takes place in extended regions (several kpc) as probed by the PAH emission, as well as the [Ne II]12.81 μm and [Ne III]15.56 μm emissions. The behavior of the integrated PAH emission and 9.7 μm silicate feature is similar to that of local starburst galaxies. We also find that the minima of the [Ne III]15.56 μm/[Ne II]12.81 μm ratio tends to be located at the nuclei and its value is lower than that of H II regions in our LIRGs and nearby galaxies. It is likely that increased densities in the nuclei of LIRGs are responsible for the smaller nuclear [Ne III]15.56 μm/[Ne II]12.81 μm ratios. This includes the possibility that some of the most massive stars in the nuclei are still embedded in ultracompact H II regions. In a large fraction of our sample, the 11.3 μm PAH emission appears more extended than the dust 5.5 μm continuum emission. We find a dependency of the 11.3 μm PAH/7.7 μm PAH and [Ne II]12.81 μm/11.3 μm PAH ratios with the age of the stellar populations. Smaller and larger ratios, respectively, indicate recent star formation. The estimated warm (300K <T< 1000K) molecular hydrogen masses are of the order of 108 M ⊙, which are similar to those found in ULIRGs, local starbursts, and Seyfert galaxies. Finally we find that the [Ne II]12.81 μm velocity fields for most of the LIRGs in our sample are compatible with a rotating disk at ∼ kpc scales, and they are in a good agreement with Hα velocity fields.
AB - We present results from the Spitzer Infrared Spectrograph spectral mapping observations of 15 local luminous infrared galaxies (LIRGs). In this paper, we investigate the spatial variations of the mid-IR emission which includes fine structure lines, molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum emission, and the 9.7 μm silicate feature. We also compare the nuclear and integrated spectra. We find that the star formation takes place in extended regions (several kpc) as probed by the PAH emission, as well as the [Ne II]12.81 μm and [Ne III]15.56 μm emissions. The behavior of the integrated PAH emission and 9.7 μm silicate feature is similar to that of local starburst galaxies. We also find that the minima of the [Ne III]15.56 μm/[Ne II]12.81 μm ratio tends to be located at the nuclei and its value is lower than that of H II regions in our LIRGs and nearby galaxies. It is likely that increased densities in the nuclei of LIRGs are responsible for the smaller nuclear [Ne III]15.56 μm/[Ne II]12.81 μm ratios. This includes the possibility that some of the most massive stars in the nuclei are still embedded in ultracompact H II regions. In a large fraction of our sample, the 11.3 μm PAH emission appears more extended than the dust 5.5 μm continuum emission. We find a dependency of the 11.3 μm PAH/7.7 μm PAH and [Ne II]12.81 μm/11.3 μm PAH ratios with the age of the stellar populations. Smaller and larger ratios, respectively, indicate recent star formation. The estimated warm (300K <T< 1000K) molecular hydrogen masses are of the order of 108 M ⊙, which are similar to those found in ULIRGs, local starbursts, and Seyfert galaxies. Finally we find that the [Ne II]12.81 μm velocity fields for most of the LIRGs in our sample are compatible with a rotating disk at ∼ kpc scales, and they are in a good agreement with Hα velocity fields.
KW - Galaxies: active
KW - Galaxies: nuclei
KW - Galaxies: starburst
KW - Galaxies: structure
KW - Infrared: galaxies
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U2 - 10.1088/0067-0049/188/2/447
DO - 10.1088/0067-0049/188/2/447
M3 - Article
AN - SCOPUS:77953170333
SN - 0067-0049
VL - 188
SP - 447
EP - 472
JO - Astrophysical Journal, Supplement Series
JF - Astrophysical Journal, Supplement Series
IS - 2
ER -