Browsing by Author "Alonso-Herrero, A."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- HERSCHEL observations of far-infrared cooling lines in intermediate redshift (ultra)-luminous infrared galaxiesRigopoulou, D.; Hopwood, R.; Magdis, G. E.; Thatte, N.; Swinyard, B. M.; Farrah, D.; Huang, J. S.; Alonso-Herrero, A.; Bock, J. J.; Clements, D. L.; Cooray, A.; Griffin, M. J.; Oliver, S.; Pearson, C.; Riechers, D. A.; Scott, D.; Smith, A.; Vaccari, M.; Valtchanov, I.; Wang, L. (IOP Publishing Ltd., 2014-01)We report the first results from a spectroscopic survey of the [C II] 158 mu m line from a sample of intermediate redshift (0.2 < z < 0.8) (ultra)-luminous infrared galaxies, (U) LIRGs (L-IR > 10(11.5) L-circle dot), using the Spectral and Photometric Imaging REceiver-Fourier Transform Spectrometer on board the Herschel Space Observatory. This is the first survey of [C II] emission, an important tracer of star formation, at a redshift range where the star formation rate density of the universe increases rapidly. We detect strong [C II] 158 mu m line emission from over 80% of the sample. We find that the [C II] line is luminous, in the range (0.8-4) x 10(-3) of the far-infrared continuum luminosity of our sources, and appears to arise from photodissociation regions on the surface of molecular clouds. The L-[C II]/L-IR ratio in our intermediate redshift (U) LIRGs is on average similar to 10 times larger than that of local ULIRGs. Furthermore, we find that the L-[C II]/L-IR and L-[C II]/LCO(1-0) ratios in our sample are similar to those of local normal galaxies and high-z star-forming galaxies. ULIRGs at z similar to 0.5 show many similarities to the properties of local normal and high-z star-forming galaxies. Our findings strongly suggest that rapid evolution in the properties of the star-forming regions of (U) LIRGs is likely to have occurred in the last 5 billion years.
- Mid- to far-infrared properties of star-forming galaxies and active galactic nucleiMagdis, G. E.; Rigopoulou, D.; Helou, G.; Farrah, D.; Hurley, P.; Alonso-Herrero, A.; Bock, J.; Burgarella, D.; Chapman, S.; Charmandaris, V.; Cooray, A.; Dai, Y. S.; Dale, D.; Elbaz, D.; Feltre, A.; Hatziminaoglou, E.; Huang, J. S.; Morrison, G.; Oliver, S.; Page, M.; Scott, D.; Shi, Y. (EDP SCIENCES, 2013-10)We study the mid- to far-IR properties of a 24 mu m-selected flux-limited sample (S-24 > 5mJy) of 154 intermediate redshift (< z > similar to 0.15), infrared luminous galaxies, drawn from the 5 Milli-Jansky Unbiased Spitzer Extragalactic Survey. By combining existing mid-IR spectroscopy and new Herschel SPIRE submm photometry from the Herschel Multi-tiered Extragalactic Survey, we derived robust total infrared luminosity (L-IR) and dust mass (M-dust) estimates and infered the relative contribution of the AGN to the infrared energy budget of the sources. We found that the total (8-1000 mu m) infrared emission of galaxies with weak 6.2 mu m PAH emission (EW6.2 <= 0.2 mu m) is dominated by AGN activity, while for galaxies with EW6.2 > 0.2 mu m more than 50% of the L-IR arises from star formation. We also found that for galaxies detected in the 250-500 mu m Herschel bands an AGN has a statistically insignificant effect on the temperature of the cold dust and the far-IR colours of the host galaxy, which are primarily shaped by star formation activity. For star-forming galaxies we reveal an anti-correlation between the L-IR-to-rest-frame 8 mu m luminosity ratio, IR8 = L-IR/L-8 and the strength of PAH features. We found that this anti-correlation is primarily driven by variations in the PAHs emission, and not by variations in the 5-15 mu m mid-IR continuum emission. Using the [NeIII]/[NeII] line ratio as a tracer of the hardness of the radiation field, we confirm that galaxies with harder radiation fields tend to exhibit weaker PAH features, and found that they have higher IR8 values and higher dust-mass-weighted luminosities (L-IR/M-dust), the latter being a proxy for the dust temperature (T-d). We argue that these trends originate either from variations in the environment of the star-forming regions or are caused by variations in the age of the starburst. Finally, we provide scaling relations that will allow estimating L-IR, based on single-band observations with the mid-infrared instrument, on board the upcoming James Webb Space Telescope.