Color Magnitude Relation and Morphology of Low-Redshift ULIRGs in SDSS - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado




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Abstract: We present color-magnitude and morphological analysis of 54 low-redshiftULIRGs, a subset of the IRAS 1Jy sample Kim and Sanders, 1998, in the SDSS. TheULIRGs are on average 1 magnitude brighter in M0.1r than the SDSS galaxieswithin the same redshift range. The majority of the ULIRGs ~87% have thecolors typical of the blue cloud, and only 4 sources ~7% are located in thered sequence. While ULIRGs are popularly thought to be precursors to a QSOphase, we find few ~6% in the -green valley- where the majority of the X-rayand IR selected AGNs are found, and none of which harbors an AGN. For the 14previously spectroscopic identified AGNs ~28%, we perform PSF subtractionsand find that on average the central point sources contribute less than onethird to the total luminosity, and that their high optical luminosities andoverall blue colors are apparently the result of star formation activity of thehost galaxies. Visual inspection of the SDSS images reveals a wide range ofdisturbed morphologies. A detailed morphology analysis using Gini and M20coefficients shows that slightly less than one half ~42% in g band of theULIRGs are located in the region where most local mergers are found. Theheterogeneous distribution of ULIRGs in the G-M20 space is qualitativelyconsistent with the results found by numerical simulations of disk-diskmergers. Our study also shows that the measured morphological parameters aresystematically affected by the SNR and thus the merging galaxies can appear atvarious regions in the G-M20 space. In general, our results reinforce the viewthat ULIRGs contain young stellar populations and are mergers in progress. Ourstudy provides a uniform comparison sample for studying ULIRGs at higherredshifts such as Spitzer mid-IR selected ULIRGs at z=1~2 and submm galaxies.



Autor: Yuxi Chen, James D. Lowenthal, Min S. Yun

Fuente: https://arxiv.org/







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