Minjin Kim

PRECISE BLACK HOLE MASSES FROM MEGAMASER DISKS: BLACK HOLE-BULGE RELATIONS AT LOW MASS

The black hole (BH)-bulge correlations have greatly influenced the last decade of efforts to understand galaxy evolution. Current knowledge of these correlations is limited predominantly to high BH masses (M BH108 M ☉) that can be measured using direct stellar, gas, and maser kinematics. These objects, however, do not represent the demographics of more typical L < L* galaxies. This study transcends prior limitations to probe BHs that are an order of magnitude lower in mass, using BH mass measurements derived from the dynamics of H2O megamasers in circumnuclear disks. The masers trace the Keplerian rotation of circumnuclear molecular disks starting at radii of a few tenths of a pc from the central BH. Modeling of the rotation curves, presented by Kuo et al., yields BH masses with exquisite precision. We present stellar velocity dispersion measurements for a sample of nine megamaser disk galaxies based on long-slit observations using the B&C spectrograph on the Dupont telescope and the Dual Imaging Spectrograph on the 3.5 m telescope at Apache Point. We also perform bulge-to-disk decomposition of a subset of five of these galaxies with Sloan Digital Sky Survey imaging. The maser galaxies as a group fall below the M BH-σ* relation defined by elliptical galaxies. We show, now with very precise BH mass measurements, that the low-scatter power-law relation between M BH and σ* seen in elliptical galaxies is not universal. The elliptical galaxy M BH-σ* relation cannot be used to derive the BH mass function at low mass or the zero point for active BH masses. The processes (perhaps BH self-regulation or minor merging) that operate at higher mass have not effectively established an M BH-σ* relation in this low-mass regime.

CONSTRAINTS ON THE STAR FORMATION RATE IN ACTIVE GALAXIES

The [O ii] k3727 emission line is often used as an indicator of star formation rate in extragalactic surveys, and it canbeanequallyeffectivetracerofstarformationinsystemscontainingluminousactivegalacticnuclei(AGNs).In order to investigate the ongoing star formation rate of the host galaxies of AGNs, we measured the strength of [Oii] and other optical emission lines from a large sample (� 3600) of broad-line (type 1) AGNs selected from the Sloan Digital Sky Survey. We performed a set of photoionization calculations to help evaluate the relative contribution of stellar and nonstellar photoionization to the observed strength of [O ii]. Consistent with the 2005 study by Ho, we findthattheobserved[Oii]emissioncanbeexplainedentirelybyphotoionizationfromtheAGNitself,withlittleor no additional contribution from H ii regions. This indicates that the host galaxies of type 1 AGNs experience very modest star formation concurrent with the optically active phase of the nucleus. By contrast, we show that the sample of ‘‘type 2’’ quasars selected from the Sloan Digital Sky Survey does exhibit substantially stronger [O ii] emission, consistent with an elevated level of star formation, a result that presents a challenge to the simplest form of the AGN unification model. Subject headingg galaxies: active — galaxies: nuclei — galaxies: Seyfert — galaxies: starburst — quasars: general

The Origin of the Intrinsic Scatter in the Relation Between Black Hole Mass and Bulge Luminosity for Nearby Active Galaxies

We investigate the origin of the intrinsic scatter in the correlation between black hole mass ( -->MBH) and bulge luminosity ( -->Lbul) in a sample of 45 massive, local ( -->z 0.35) type 1 active galactic nuclei (AGNs). We derive -->MBH from published optical spectra assuming a spherical broad-line region, and -->Lbul from detailed two-dimensional decomposition of archival optical Hubble Space Telescope images. AGNs follow the -->MBH − Lbul relation of inactive galaxies, but the zero point is shifted by an average of -->Δ log MBH ≈ − 0.3 dex. We show that the magnitude of the zero point offset, which is responsible for the intrinsic scatter in the -->MBH − Lbul relation, is correlated with several AGN and host galaxy properties, all of which are ultimately related to, or directly impact, the BH mass accretion rate. At a given bulge luminosity, sources with higher Eddington ratios have lower -->MBH. The zero point offset can be explained by a change in the normalization of the virial product used to estimate -->MBH, in conjunction with modest BH growth (~10%-40%) during the AGN phase. Galaxy mergers and tidal interactions appear to play an important role in regulating AGN fueling in low-redshift AGNs.

AKARI NEAR-INFRARED SPECTROSCOPY OF LUMINOUS INFRARED GALAXIES

We present the AKARI near-infrared (NIR; 2.5-5 μm) spectroscopic study of 36 (ultra)luminous infrared galaxies ((U)LIRGs) at z = 0.01-0.4. We measure the NIR spectral features including the strengths of 3.3 μm polycyclic aromatic hydrocarbon emission and hydrogen recombination lines (Brα and Brβ), optical depths at 3.1 and 3.4 μm, and NIR continuum slope. These spectral features are used to identify optically elusive, buried active galactic nuclei (AGNs). We find that half of the (U)LIRGs optically classified as non-Seyferts show AGN signatures in their NIR spectra. Using a combined sample of (U)LIRGs with NIR spectra in the literature, we measure the contribution of buried AGNs to the infrared luminosity from the spectral energy distribution fitting to the IRAS photometry. The contribution of these buried AGNs to the infrared luminosity is 5%-10%, smaller than the typical AGN contribution of (U)LIRGs including Seyfert galaxies (10%-40%). We show that NIR continuum slopes correlate well with WISE [3.4]-[4.6] colors, which would be useful for identifying a large number of buried AGNs using the WISE data.

Decomposition of the Host Galaxies of Active Galactic Nuclei Using Hubble Space Telescope Images

Investigating the link between supermassive black hole and galaxy evolution requires careful measurements of the properties of the host galaxies. We perform simulations to test the reliability of a two-dimensional image-fitting technique to decompose the host galaxy and the active galactic nucleus (AGN), especially on images obtained using cameras on board the Hubble Space Telescope (HST), such as the Wide-Field Planetary Camera 2, the Advanced Camera for Surveys, and the Near-Infrared Camera and Multi-Object Spectrometer. We quantify the relative importance of spatial, temporal, and color variations of the point-spread function (PSF). To estimate uncertainties in AGN-to-host decompositions, we perform extensive simulations that span a wide range in AGN-to-host galaxy luminosity contrast, signal-to-noise ratio, and host galaxy properties (size, luminosity, central concentration). We find that realistic PSF mismatches that typically afflict actual observations systematically lead to an overestimate of the flux of the host galaxy. Part of the problem is caused by the fact that the HST PSFs are undersampled. We demonstrate that this problem can be mitigated by broadening both the science and the PSF images to critical sampling without loss of information. Other practical suggestions are given for optimal analysis of HST images of AGN host galaxies.

Rest-Frame Optical Spectra and Black Hole Masses of 3 < z < 6 Quasars

We present the rest-frame optical spectral properties of 155 luminous quasars at 3.3<z<6.4 taken with the AKARI space telescope, including the first detection of H

NEW ESTIMATORS OF BLACK HOLE MASS IN ACTIVE GALACTIC NUCLEI WITH HYDROGEN PASCHEN LINES

\alpha

MAGELLAN SPECTROSCOPY OF LOW-REDSHIFT ACTIVE GALACTIC NUCLEI

emission line as far out as z~6. We extend the scaling relation between the rest-frame optical continuum and line luminosity of active galactic nuclei (AGNs) to the high luminosity, high redshift regime that has rarely been probed before. Remarkably, we find that a single log-linear relation can be applied to the 5100

Correlation between Galaxy Mergers and Luminous AGN

{\rm \AA}

The Cosmic Infrared Background Experiment (CIBER): A Sounding Rocket Payload to Study the near Infrared Extragalactic Background Light

and H