  Infrared colours of star-forming galaxies and a flux calibration of ISOCAM ELAIS catalogues; Morel, Thierry  in Exploiting the ISO Data Archive. Infrared Astronomy in the Internet Age (2003, February 01) We present J and K-band near-infrared photometry of a sample of ISOCAM sources detected by the European Large Area ISO-Survey (ELAIS). All of the high-reliability LW2 (6.7 μm) sources and 80 per cent of ... [more ▼] We present J and K-band near-infrared photometry of a sample of ISOCAM sources detected by the European Large Area ISO-Survey (ELAIS). All of the high-reliability LW2 (6.7 μm) sources and 80 per cent of the LW3 (15 μm) sources are identified in the near-IR survey reaching K â 17.5 mag. The near- to mid-IR flux ratios can effectively be used to separate stars from galaxies in mid-IR surveys: at 6.7 μm, 80 per cent of the identified ELAIS objects are stars while at 15 μm 80 per cent are galaxies. The stars are then used to perform an accurate new calibration of the ELAIS ISOCAM data at both 6.7 and 15 μm: we adopt values of 1.23 and 1.05 ADU/gain/s/mJy for the LW2 and LW3 filters, respectively. The ISOCAM ELAIS survey is found to mostly detect strongly star-forming late-type galaxies. We show that near to mid-IR colour-colour diagrams can be used to further classify galaxies, as well as study star-formation. In a [15/2.2] vs. [6.7/2.2] plot the Hubble type of a galaxy can be roughly estimated from its position along the diagonal ([6.7/15] = 1) and the star-forming efficiency from a galaxys departure from the diagonal (eg. [6.7/15] <1). The ELAIS galaxies yield an average mid-IR flux ratio LW2/LW3 =0.67 ± 0.27. We discuss this [6.7/15] ratio as a star formation tracer using ISO and IRAS data of a local comparison sample. The [2.2/15] ratio is also found to be a good indicator of activity level in galaxies and conclude that the drop in the [6.7/15] ratio seen in strongly star-forming galaxies is a result of both an increase of 15 μm emission and an apparent depletion of 6.7 μm emission. [less ▲] Detailed reference viewed: 5 (1 ULg)Near- and mid-infrared colours of star-forming galaxies in European Large Area ISO Survey fields; Morel, Thierry ; et alin Monthly Notices of the Royal Astronomical Society (2002), 337 We present J- and K-band near-infrared (near-IR) photometry of a sample of mid-infrared (mid-IR) sources detected by the Infrared Space Observatory (ISO) as part of the European Large Area ISO Survey ... [more ▼] We present J- and K-band near-infrared (near-IR) photometry of a sample of mid-infrared (mid-IR) sources detected by the Infrared Space Observatory (ISO) as part of the European Large Area ISO Survey (ELAIS) and study their classification and star-forming properties. We have used the Preliminary ELAIS Catalogue for the 6.7-μm (LW2) and 15-μm (LW3) fluxes. All of the high-reliability LW2 sources and 80 per cent of the LW3 sources are identified in the near-IR survey reaching K~ 17.5 mag. The near-IR/mid-IR flux ratios can effectively be used to separate stars from galaxies in mid-IR surveys. The stars detected in our survey region are used to derive a new accurate calibration for the ELAIS ISOCAM data in both the LW2 and LW3 filters. We show that near- to mid-IR colour-colour diagrams can be used to classify galaxies further, as well as to study star formation. The ELAIS ISOCAM survey is found mostly to detect strongly star-forming late-type galaxies, possibly starburst-powered galaxies, and it also picks out obscured active galactic nuclei. The ELAIS galaxies yield an average mid-IR flux ratio LW2/LW3 = 0.67 +/- 0.27. We discuss the f[SUB]ν[/SUB](6.7 μ m)/f[SUB]ν[/SUB](15 μ m) ratio as a star formation tracer using ISO and IRAS data of a local comparison sample. We find that the f[SUB]ν[/SUB](2.2 μ m)/f[SUB]ν[/SUB](15 μ m) ratio is also a good indicator of activity level in galaxies and conclude that the drop in the f[SUB]ν[/SUB](6.7 μ m)/f[SUB]ν[/SUB](15 μ m) ratio seen in strongly star-forming galaxies is a result of both an increase of 15-μm emission and an apparent depletion of 6.7-μm emission. Near-IR together with the mid-IR data make it possible to estimate the relative amount of interstellar matter in the galaxies. [less ▲] Detailed reference viewed: 12 (1 ULg) |
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