arXiv subjects

L. Colina

Publications and source records attributed to L. Colina.

148 records · Page 9Linked to original sources

arXiv1999

HST Observations of the Serendipitous X-ray Companion to Mrk 273: Cluster at z=0.46?

We have used HST I-band images to identify Mrk 273X, the very unusual high-redshift X-ray-luminous Seyfert 2 galaxy found by ROSAT in the same field-of-view as Mrk 273. We have measured the photometric properties of Mrk 273X and have also analyzed the luminosity distribution of the faint galaxy population seen in the HST image. The luminosity of the galaxy and the properties of the surrounding environment suggest that Mrk 273X is the brightest galaxy in a relatively poor cluster at a redshift near 0.46. Its off-center location in the cluster and the presence of other galaxy groupings in the HST image may indicate that this is a dynamically young cluster on the verge of merging with its neighboring clusters. We find that Mrk 273X is a bright featureless elliptical galaxy with no evidence for a disk. It follows the de Vaucouleurs (r^{1/4}) surface brightness law very well over a range of 8 magnitudes. Though the surface brightness profile does not appear to be dominated by the AGN, the galaxy has very blue colors that do appear to be produced by the AGN. Mrk 273X is most similar to the IC 5063 class of active galaxies --- a hybrid Sy 2 / powerful radio galaxy.

astro-ph↗

arXiv1999

A Morphological Classification Scheme for ULIRGs: Evidence for Multiple Mergers

We have used the Hubble Space Telescope (HST) to study a large sample of ultraluminous IR galaxies (ULIRGs). With a rich legacy database of 150 high-resolution images, we are studying the fine-scale structure of this unique collection of violently starbursting systems. We review here some of the latest results from our survey. We present a simple morphological classification scheme, consisting of 4 ULIRG classes, showing that there is very little luminosity variation (in the mean) between the classes, and that there is equal likelihood of a ULIRG being a recent merger (single) as an on-going collision (multiple). It now appears that the fraction of ULIRGs that show evidence for interaction or merging is very close to 100%. A star-like nucleus is seen in about 15% of the ULIRGs, for which the dominant power source may be a dust-enshrouded AGN/QSO. Many of the results on ULIRGs are pointing to a complicated dynamical history for this sample of galaxies. One possible explanation for this dynamical diversity is the multiple-merger model proposed by Taniguchi & Shioya (1998, ApJ, 501, L167). We present strong observational evidence for multiple mergers among a large fraction of our ULIRG sample. If this is a valid model, then ULIRGs could be the merger remnants of an earlier generation of compact groups of galaxies.

astro-ph↗

arXiv1998

HST NICMOS and WFPC2 Imaging of Ultraluminous Galaxies

HST is used to study the power sources and the interaction-induced tidal disturbances within the most luminous galaxies in the local universe -- the Ultra-Luminous IR Galaxies (ULIRGs) -- through the use of I-band images with WFPC2 and H-band images with NICMOS. Such images are probing for the first time the fine-scale structures in the strong collision-disturbed morphologies of these rare and exotic galaxies.

astro-ph↗

arXiv1998

Molecular gas in water megamaser active galaxies

We have searched for molecular gas towards the nucleus of four galaxies known to harbor a water vapor megamaser. CO(1-->0) emission of NGC 2639 and NGC 5506 was strong enough to allow us to map their inner regions. Weak emission from Mrk 1210 was detected and Mrk 1 was not detected at all. We report the tentative detection of the CO(2-->1) line in NGC 5506. After this work, 12 of the 18 known galaxies harboring a water vapor megamaser have been observed in CO.

astro-ph↗