Tuesday 2/19/13

Want to measure TIR in your favorite galaxy using Spitzer and/or Herschel bands? The first paper below (Galametz et al.) provides calibrations in order to do that. The second paper (Agius et al.) might be most interesting for me, comparing the properties of IR-bright and faint early-type galaxies. Some differences in concentration as well as expected things like UV/optical colors. The third abstract is for a conference proceeding (Combes), but looks like it provides a short and sweet overview of where we are on high-z molecular observations, possibly IRAM-biased. Enjoy!

Title: Calibration of the total infrared luminosity of nearby galaxies from Spitzer and Herschel bands
Authors: Galametz, M.; Kennicutt, R. C.; Calzetti, D.; Aniano, G.; Draine, B. T.; Boquien, M.; Brandl, B.; Croxall, K. V.; Dale, D. A.; Engelbracht, C. W.; Gordon, K. D.; Groves, B.;Hao, C.-N.; Helou, G.; Hinz, J. L.; Hunt, L. K.; Johnson, B. D.; Li, Y.; Murphy, E.; Roussel, H.; Sandstrom, K.; Skibba, R. A.; Tabatabaei, F. S.
Bibliographic Code: 2013arXiv1302.4363G


We present new empirical calibrations to estimate resolved and integrated total infrared luminosities from Spitzer and Herschel bands used as monochromatic or combined tracers. We base our calibrations on resolved elements of nearby galaxies (3 to 30 Mpc) observed with Herschel. We perform a resolved SED modelling of these objects using the Draine and Li (2007) dust models and investigate the influence of the addition of SPIRE measurements in the estimation of LTIR. We find that using data up to 250 um leads to local LTIR values consistent with those obtained with a complete coverage (up to 500 um) within 10 per cent for most of our resolved elements. We then study the distribution of energy in the resolved SEDs of our galaxies. The bulk of energy (30-50 per cent) is contained in the (70-160 um) band. The (24-70 um) fraction decreases with increasing metallicity. The (160-1100 um) submillimeter band can account for up to 25 per cent of the LTIR in metal-rich galaxies. We investigate the correlation between TIR surface brightnesses/luminosities and monochromatic Spitzer and Herschel surface brightnesses/luminosities. The three PACS bands can be used as reliable monochromatic estimators of the LTIR, the 100 um band being the most reliable monochromatic tracer. There is also a strong correlation between the SPIRE 250um and LTIR, although with more scatter than for the PACS relations. We also study the ability of our monochromatic relations to reproduce integrated LTIR of nearby galaxies as well as LTIR of z=1-3 sources. Finally, we provide calibration coefficients that can be used to derive TIR surface brightnesses/luminosities from a combination of Spitzer and Herschel surface brightnesses/fluxes and analyse the associated uncertainties.

Title: GAMA/H-ATLAS: Linking the Properties of Sub-mm Detected and Undetected Early-Type Galaxies: I. z$\le$0.06 Sample
Authors: Agius, N. K.; Sansom, A. E.; Popescu, C. C.; Andrae, E.; Baes, M.; Baldry, I.; Bourne, N.; Brough, S.; Clark, C. J. R.; Conselice, C.; Cooray, A.; Dariush, A.; De Zotti, G.;Driver, S. P.; Dunne, L.; Eales, S. A.; Foster, C.; Gomez, H. L.; Haußler, B.; Hopkins, A. M.; Hopwood, R.; Ivison, R. J.; Kelvin, L. S.; Lara-Lopez, M. A.; Liske, J.; Lopez-Sanchez, A.; Loveday, J.; Maddox, S.; Madore, B.; Phillipps, S.; Robotham, A.; Rowlands, K.; Seibert, M.; Smith, M. W. L.; Temi, P.; Tuffs, R.; Valiante, E.
Bibliographic Code: 2013arXiv1302.4276A


We present two large, nearby (0.013$\le$z$\le$0.06) samples of Early-Type Galaxies (ETGs): a visually classified sample of 220 ETGs, created using source-matched data from the Galaxy and Mass Assembly (GAMA) database with FIR/sub-mm detections from $Herschel$-ATLAS; and a visually classified sample of 551 ETGs which are undetected with $Herschel$-ATLAS. Active galactic nuclei (AGN) are removed from our samples using optical emission line diagnostics. These samples are scrutinised to determine characteristics of sub-mm detected versus undetected ETGs. We find similarities in the stellar mass distributions of the two ETG samples but testing other properties uncovers significant differences. The sub-mm detected sample is shown to have lower concentration and S\’ersic indices than those in the undetected sample – a result which may be linked to the presence of dust in the former. Optical and UV-optical colours are also shown to be much bluer, indicating that the dust is linked with recent star formation. The intrinsic effective radii are on average 1.5 times larger for the sub-mm detected ETGs. Surface densities and groups data from the GAMA database are examined for the two samples, leading to the conclusion that dusty ETGs inhabit sparser environments than non-dusty ETGs in the nearby universe, although environments of the brightest ETGs are shown to differ the least. Modified Planck functions are fit to the H-ATLAS detected PACS and SPIRE fluxes for ETGs with sub-mm flux densities of at least 3$\sigma$ in the 350$\mu$m SPIRE band, giving a resultant mean cold dust temperature of T$_{d}$=22.1K, with a range of 9-30K. The corresponding mean dust mass is 1.8$\times10^{7}$M$_{\odot}$, with a range of (0.08-35.0)$\times10^{7}$M$_{\odot}$. The dust masses calculated from these fits, normalised by stellar mass, are shown to increase with decreasing stellar mass and bluer colours.

Title: Molecular gas in high redshift galaxies
Authors: Combes, Francoise
Bibliographic Code: 2013arXiv1302.4184C


Recent observations with the IRAM instruments have allowed to explore the star formation efficiency in galaxies as a function of redshift, in detecting and mapping their molecular gas. Some galaxies stand on what is called the "main sequence", forming stars with a rate that can be sustained over time-scales of 1 Gyr, some are starbursts, with a much shorter depletion time. Star formation was more active in the past, partly because galaxies contained a larger gas fraction, and also because the star formation efficiency was higher. The global Kennicutt-Schmidt relation was however similar until z \sim 2.5. Magnification by gravitational lenses have been used to explore in details galaxies at higher redshift up to 6. Herschel has discovered many of these candidates, and their redshift has been determined through the CO lines. ALMA is beginning to extend considerably these redshift searches, with its broad-band receivers, for a large range of objects too obscured to be seen in the optical.

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