Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOptical and Near-Infrared Imaging of the IRAS 1-Jy Sample of Ultraluminous Infrared Galaxies: II. The Analysis
112
0
0.0
(
0
)
Authors
S. Veilleux
Ask ChatGPT about the research
No Arabic abstract
The present paper discusses the results from an analysis of the images presented in Paper I (astro-ph/0207373) supplemented with new spectroscopic data obtained at Keck. All but one object in the 1-Jy sample show signs of a strong tidal interaction/merger. Multiple mergers involving more than two galaxies are seen in no more than 5 of the 118 (< 5%) systems. None of the 1-Jy sources is in the first-approach stage of the interaction, and most (56%) of them harbor a single disturbed nucleus and are therefore in the later stages of a merger. Seyfert galaxies (especially those of type 1), warm ULIGs (f_{25}/f_{60} > 0.2) and the more luminous systems (> 10^{12.5} L_sun) all show a strong tendency to be advanced mergers with a single nucleus. An analysis of the surface brightness profiles of the host galaxies in single-nucleus sources reveals that about 73% of the R and K surface brightness profiles are fit adequately by an elliptical-like R^{1/4}-law. These elliptical-like 1-Jy systems have luminosities, half-light radii, and R-band axial ratio distribution that are similar to those of normal (inactive) intermediate-luminosity ellipticals and follow with some scatter the same mu_e - r_e relation. These elliptical-like hosts are most common among merger remnants with Seyfert 1 nuclei (83%), Seyfert 2 optical characteristics (69%) or mid-infrared (ISO) AGN signatures (80%). In general, the results from the present study are consistent with the merger-driven evolutionary sequence ``cool ULIGs --> warm ULIGs --> quasars, although there are many exceptions. (abridged)
rate research
Read More
An imaging survey of the {em IRAS} 1-Jy sample of 118 ultraluminous infrared galaxies was conducted at optical (R) and near-infrared (K) wavelengths using the University of Hawaii 2.2m telescope. The methods of observation and data reduction are described. An R and K atlas of the entire sample is presented along with some of the basic astrometric and photometric parameters derived from these images. A more detailed analysis of these data is presented in a companion paper (Veilleux, Kim, & Sanders 2002; astro-ph/0207401).
We present a new sample of distant ultraluminous infrared galaxies. The sample was selected from a positional cross--correlation of the IRAS Faint Source Catalog with the FIRST database. Objects from this set were selected for spectroscopy by virtue of following the well-known star-forming galaxy correlation between 1.4 GHz and 60 micron flux, and by being optically faint on the POSS. Optical identification and spectroscopy were obtained for 108 targets at the Lick Observatory 3m telescope. Most objects show spectra typical of starburst galaxies, and do not show the high ionization lines of active galactic nuclei. The redshift distribution covers 0.1 < z < 0.9, with 13 objects at z > 0.5 and an average redshift of 0.31. K-band images were obtained at the IRTF, Lick, and Keck observatories in sub-arcsec seeing of all optically identified targets. About 2/3 of the objects appear to be interacting galaxies, while the other 1/3 appear to be normal. Nearly all the identified objects have far-IR luminosities greater than 10^11 L_sun, and ~25% have L_FIR > 10^12 L_sun.
We present HST WFPC2 V band imaging for 23 Ultraluminous Infrared Galaxies taken from the QDOT redshift survey. The fraction of sources observed to be interacting is 87%. Most of the merging systems show a number of compact `knots, whose colour and brightness differ substantially from their immediate surroundings. Colour maps for nine of the objects show a non-uniform colour structure. Features include blue regions located towards the centres of merging systems which are likely to be areas of enhanced star formation, and compact red regions which are likely to be dust shrouded starbursts or AGN. The host galaxies of the QSOs in the sample were found to be either interacting systems or ellipticals. Our data shows no evidence that ULIRGs are a simple transition stage between galaxy mergers and QSOs. We propose an alternative model for ULIRGs based on the morphologies in our sample and previous N-body simulations. Under this model ULIRGs as a class are much more diverse than a simple transition between galaxy merger and QSO. The evolution of IR power source and merger morphology in ULIRGs is driven solely by the local environment and the morphologies of the merger progenitors.
We present low resolution near-infrared spectroscopy of an unbiased sample of 24 ultraluminous infrared galaxies (ULIRGs), selected from samples previously observed spectroscopically in the mid-infrared with the Infrared Space Observatory (ISO). Qualitatively, the near-infrared spectra resemble those of starbursts. Only in one ULIRG, IRAS 04114-5117E, do we find spectroscopic evidence for AGN activity. The spectroscopic classification in the near-infrared is in very good agreement with the mid-infrared one. For a subset of our sample for which extinction corrections can be derived from Pa-alpha and Br-gamma, we find rather high Pa-alpha luminosities, in accordance with the powering source of these galaxies being star formation.[Fe] emission is strong in ULIRGs and may be linked to starburst and superwind activity. Additionally, our sample includes two unusual objects. The first, IRAS F00183-7111, exhibits extreme [Fe] emission and the second, IRAS F23578-5307, is according to our knowledge one of the most luminous infrared galaxies in H2 rotation-vibration emission.
We present a study of the optical spectral properties of 115 ultraluminous infrared galaxies (ULIRGs) in the southern sky. Using the optical spectra obtained at CTIO 4 m and provided by the 2dF Galaxy Redshift Survey and the 6dF Galaxy Survey, we measure emission line widths and fluxes for spectral classification. We determine the spectral types of ULIRGs with H_alpha measurement using the standard diagnostic diagrams. For ULIRGs without H_alpha measurement, we determine their spectral types using the plane of flux ratio between [OIII]_lambda5007 and H_beta versus [OIII] line width based on our new empirical criterion. This criterion is efficient to distinguish active galactic nuclei (AGNs) from non-AGN galaxies with completeness and reliability of about 90 per cent. The sample of 115 ULIRGs is found to consist of 8 broad-line AGNs, 49 narrow-line AGNs, and 58 non-AGNs. The AGN fraction is on average 50 per cent and increases with infrared luminosity and IRAS 25-60 micron colour, consistent with previous studies. The IRAS 25-60 micron colour distributions are significantly different between AGN and non-AGN ULIRGs, while their IRAS 60-100 micron colour distributions are similar.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
