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Register a new userHost galaxies of 2MASS-selected QSOs to redshift 0.3
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We present and discuss optical imaging of 76 AGN which represent the 2MASS-selected sample for z<0.3, from a full list of 243. They are found to have dust-obscured nuclei, residing in host galaxies that show a high fraction (>70%) of tidal interactions. The derived luminosities of the AGN and host galaxies are similar to traditionally-selected AGN, and they may comprise some 40% of the total AGN population at low redshift. We have measured a number of host galaxy properties, and discuss their distributions and interrelations. We compare the 2MASS AGN with optically selected samples and the IRAS-selected galaxy samples, and discuss the differences in terms of merger processes and initial conditions.
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We have obtained optical imaging with the Canada France Hawaii Telescope (CFHT) of 21 2MASS-selected QSOs of redshift greater than 0.3. This paper complements the sample of lower redshift 2MASS QSOs previously published. The QSOs have higher overall and nuclear luminosity, bluer colours, and higher ratio of nuclear to host flux than the lower redshift sample. From these and other properties, we argue that the sample is consistent with the emergence of the AGN from dusty starbursts following major tidal interactions between galaxies.
Using simple infrared color selection, 2MASS has found a large number of red, previously unidentified, radio-quiet QSOs. Although missed by UV/optical surveys, the 2MASS QSOs have K-band luminosities that are comparable to classical QSOs. This suggests the possible discovery of a previously predicted large population of dust-obscured radio-quiet QSOs. We present the results of an imaging survey of 29 2MASS QSOs observed with WFPC2 onboard the Hubble Space Telescope. I-band images, which benefit from the relative faintness of the nuclei at optical wavelengths, are used to characterize the host galaxies, measure the nuclear contribution to the total observed I-band emission, and to survey the surrounding environments. The 2MASS QSOs are found to lie in galaxies with a variety of morphologies, luminosities, and dynamical states, not unlike those hosting radio-quiet PG QSOs. Our analysis suggests that the extraordinary red colors of the 2MASS QSOs are caused by extinction of an otherwise typical QSO spectrum due to dust near the nucleus.
We present results from a pilot HST ACS deep imaging study in broad-band V of five low-redshift QSO host galaxies classified in the literature as ellipticals. The aim of our study is to determine whether these early-type hosts formed at high redshift and have since evolved passively, or whether they have undergone relatively recent mergers that may be related to the triggering of the nuclear activity. We perform two-dimensional modeling of the light distributions to analyze the host galaxies morphology. We find that, while each host galaxy is reasonably well fitted by a de Vaucouleurs profile, the majority of them (4/5) reveal significant fine structure such as shells and tidal tails. These structures contribute between ~5% and 10% to the total V-band luminosity of each host galaxy within a region of r ~ 3 r_eff and are indicative of merger events that occurred between a few hundred Myr and a Gyr ago. These timescales are comparable to starburst ages in the QSO hosts previously inferred from Keck spectroscopy. Our results thus support a consistent scenario in which most of the QSO host galaxies suffered mergers with accompanying starbursts that likely also triggered the QSO activity in some way, but we are also left with considerable uncertainty on physical mechanisms that might have delayed this triggering for several hundred Myr after the merger.
We present optical observations of two remarkable new AGN discovered by the Two-Micron All Sky Survey. Both are classified as QSOs based on their optical spectra, near-IR colors, and near-IR and [O III]5007 luminosities, but their optical polarizations are among the highest seen for non-blazar AGN; approaching 15% for 2MASSI J151653.2+190048. The polarized light spectrum for each object exhibits broad Balmer emission lines, but lacks the narrow lines that are evident in the total light spectrum. This is most pronounced for the Type-1.5 object 2MASSI J165939.7+183436, where broad lines dominate only in polarized light. The polarization properties of these AGN suggest that dust near the nucleus at least partially obscures the AGN and that material probably intermixed with the narrow line-emitting gas scatters nuclear light into our line of sight. These QSOs illustrate the variety of highly polarized AGN that have been missed by traditional optical search techniques, and demonstrate that such objects are exposed by surveys in the near-IR.
We present the measurement and interpretation of the angular power spectrum of nearby galaxies in the 2MASS Redshift Survey catalog with spectroscopic redshifts up to $zapprox 0.1$. We detect the angular power spectrum up to a multipole of $ellapprox 1000$. We find that the measured power spectrum is dominated by galaxies living inside nearby galaxy clusters and groups. We use the halo occupation distribution (HOD) formalism to model the power spectrum, obtaining a fit with reasonable parameters. These HOD parameters are in agreement with the 2MASS galaxy distribution we measure toward the known nearby galaxy clusters, confirming validity of our analysis.
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