The CO Tully-Fisher Relation and Implications for the Host Galaxies of High-Redshift Quasars

The integrated line width derived from CO spectroscopy provides a powerful tool to study the internal kinematics of extragalactic objects, including quasars at high redshift, provided that the observed line width can be properly translated to more conventionally used kinematical parameters of galaxies. We show, through construction of a K-band CO Tully-Fisher relation for nearby galaxies spanning a wide range in infrared luminosity, that the CO line width measured at 20% of the peak intensity, when corrected for inclination and other effects, successfully recovers the maximum rotation velocity of the disk. The line width at 50% of the peak intensity performs much more poorly, in large part because CO lines have a wide range of profiles, which are shown to vary systematically with infrared luminosity. We present a practical prescription for converting observed CO line widths into the stellar velocity dispersion of the bulge (sigma), and then apply it to a sample of low-redshift (z < 0.2) and high-redshift (1.4 < z < 6.4) quasars to study their host galaxies. Nearby quasars roughly fall on the correlation between black hole mass and bulge stellar velocity dispersion established for inactive galaxies, but the host galaxies of the high-z quasars systematically deviate from the local M_BH-sigma relation. At a given sigma, high-z quasars have black hole masses larger by a factor of 4 relative to local galaxies, suggesting that early in the life-cycle of galaxies the development of the bulge lags behind the growth of the central black hole. An alternative explanation for these observations, which currently cannot be ruled out rigorously, is that high-redshift quasars are preferentially viewed at face-on orientations.Comment: To appear in ApJ; 10 page

Young Star Clusters in Starburst Environments

Recent high-resolution observations with the Hubble Space Telescope (HST) reveal that young star clusters of extraordinary luminosity and compactness ("super star clusters") are commonly found in starburst systems. Cluster formation appears to be a dominant mode of star formation in starbursts. The principal properties of the young clusters are summarized. A new ultraviolet HST imaging survey of the central regions of nearby galaxies indicates that young clusters form in a wide range of environments. Circumnuclear star-forming rings, in particular, are richly populated with clusters, and several examples from recent imaging studies are discussed. There has been much speculation that super star clusters represent present-day analogs of young globular clusters. I will present evidence suggesting that at least some super star clusters indeed have masses and mass densities comparable to those of evolved globular clusters in the Milky Way.Comment: Invited paper to appear in Rev. Mex. Astr. Astrofis. (1996), proceedings of Starburst Activity in Galaxies, ed. J. Franco, R. Terlevich, and G. Tenorio-Tagle. LaTex, 9 pages, including 1 postcript figure. rmaaconf.sty macros included. 3 greyscale figures (Fig. 1-3) here as jpegs, or in compressed PostScript at ftp://cfa0.harvard.edu/outgoing/lho/clusters/ (mget fig*ps.Z

Optical Spectroscopy of LINERs and Low-Luminosity Seyfert Nuclei

An unprecedentedly large number of LINERs has been discovered in a recently completed optical spectroscopic survey of nearby galaxies, allowing several statistical properties of the host galaxies and of the line-emitting regions to be examined reliably for the first time. As a consequence of the many detections and some revised classifications, the detailed demographics of emission-line nuclei have been updated from those given in older surveys. Consistent with previous studies, it is found that LINERs are extremely common in the present epoch, comprising approximately 1/3 of all galaxies with B <= 12.5 mag. If all LINERs are nonstellar in origin, then they are the dominant constituents of the active galactic nucleus population. Many fundamental characteristics of LINERs closely resemble those of low-luminosity Seyfert nuclei, although several aspects of their narrow-line regions appear to differ in a systematic manner. These differences could hold important clues to the key parameters controlling the ionization level in active nuclei. Lastly, a substantial fraction of LINERs has been found to contain a broad-line region, yielding direct evidence, at least in these objects, of a physical link between LINERs and classical Seyfert 1 nuclei and QSOs.Comment: Invited review paper to appear in The Physics of LINERs in View of Recent Observations, ed. M. Eracleous, A. P. Koratkar, L. C. Ho, and C. Leitherer (San Francisco: ASP), in press. LaTex, 29 pages. ASP Conference Series macros include

A criterion for finite rank λ\lambda-Toeplitz operators

Let $\lambda$ be a complex number in the closed unit disc $\overline{\Bbb D}$, and $\cal H$ be a separable Hilbert space with the orthonormal basis, say, ${\cal E}=\{e_n:n=0,1,2,\cdots\}$. A bounded operator $T$ on $\cal H$ is called a $\lambda$-Toeplitz operator if $$\langle Te_{m+1},e_{n+1}\rangle=\lambda\langle Te_m,e_n\rangle$$ (where $\langle\cdot,\cdot\rangle$ is the inner product on $\cal H$). The subject arises naturally from a special case of the operator equation S^*AS=\lambda A+B,\ \mbox{where $S$ is a shift on $\cal H$}, which plays an essential role in finding bounded matrix $(a_{ij})$ on $l^2(\Bbb Z)$ that solves the system of equations $$\left\{\begin{array}{lcc} a_{2i,2j}&=&p_{ij}+aa_{ij}\\ a_{2i,2j-1}&=&q_{ij}+ba_{ij}\\ a_{2i-1,2j}&=&v_{ij}+ca_{ij}\\ a_{2i-1,2j-1}&=&w_{ij}+da_{ij} \end{array}\right.$$ for all $i,j\in\Bbb Z$, where $(p_{ij})$, $(q_{ij})$, $(v_{ij})$, $(w_{ij})$ are bounded matrices on $l^2(\Bbb Z)$ and $a,b,c,d\in\Bbb C$. It is also clear that the well-known Toeplitz operators are precisely the solutions of $S^*AS=A$, when $S$ is the unilateral shift. In this paper we verify some basic issues, such as boundedness and compactness, for $\lambda$-Toeplitz operators and, our main result is to give necessary and sufficient conditions for finite rank $\lambda$-Toeplitz operators

The Central Engines of Low-Luminosity AGNs

I summarize the main characteristics of AGNs in nearby galaxies and present a physical picture of their central engines.Comment: To appear in Active Galactic Nuclei: from Central Engine to Host Galaxy, ed. S. Collin, F. Combes, & I. Shlosman (San Francisco: ASP), in pres

On the Relationship Between Radio Emission and Black Hole Mass in Galactic Nuclei

We use a comprehensive database of black hole masses and nuclear luminosities to investigate the relationship between radio emission and black hole mass. Our sample covers a wide range of nuclear activity, from nearby inactive nuclei to classical Seyfert 1 nuclei and luminous quasars. Contrary to some previous studies, we find that the radio continuum power, either integrated for the entire galaxy or isolated for the core, correlates poorly with black hole mass. The degree of nuclear radio loudness, parameterized by the radio-to-optical luminosity ratio R, also shows no clear dependence on black hole mass. Radio-loud nuclei exist in galaxies with a wide range of black hole mass, from \~ 10^6 to a few X 10^9 solar masses, and in a variety of hosts, from disk-dominated spirals to giant ellipticals. We demonstrate that R is strongly inversely correlated with L/L_E, the ratio of nuclear luminosity to the Eddington luminosity, and hence with mass accretion rate. Most or all of the weakly active nuclei in nearby galaxies are radio-loud, highly sub-Eddington systems that are plausibly experiencing advection-dominated accretion.Comment: To appear in ApJ. 14 page

The Carnegie Observatories Astrophysics Series

On the occasion of the Centennial of the Carnegie Institution of Washington, Carnegie Observatories held a series of four astrophysics symposia in Pasadena from October 2002 to February 2003. The topics of the symposia were: (1) Coevolution of Black Holes and Galaxies [Ed. L. C. Ho] (2) Measuring and Modeling the Universe [Ed. W. L. Freedman] (3) Clusters of Galaxies: Probes of Cosmological Structure and Galaxy Evolution [Ed. J. S. Mulchaey, A. Dressler, and A. Oemler] (4) Origin and Evolution of the Elements [Ed. A. McWilliam and M. Rauch] The invited papers of the symposia, which have been peer-reviewed and carefully edited, will be published in 2004 by Cambridge University Press, as the first four volumes of the Carnegie Observatories Astrophysics Series. The papers from the contributed talks and posters, along with the full set of the invited papers, are available electronically at http://www.ociw.edu/ociw/symposia/series/. The purpose of this note is to alert the community of the availability of this resource.Comment: The Carnegie Observatories Astrophysics Series is available online at http://www.ociw.edu/ociw/symposia/series

Origin and Dynamical Support of Ionized Gas in Galaxy Bulges

We combine ionized gas ([N II] 6583) and stellar central velocity dispersions for a sample of 345 galaxies, with and without active galactic nuclei (AGNs), to study the dynamical state of the nuclear gas and its physical origin. The gas dispersions strongly correlate with the stellar dispersions over the velocity range of 30-350 km/s such that sigma_g/sigma_* ~ 0.6-1.4, with an average value of 0.80. These results are independent of Hubble type (for galaxies from E to Sbc), presence or absence of a bar, or local galaxy environment. For galaxies of type Sc and later and that have sigma_* < 40 km/s, the gas seems to have a minimum threshold of sigma_g ~ 30 km/s, such that sigma_g/sigma_* always exceeds 1. Within the sample of AGNs, sigma_g/sigma_* increases with nuclear luminosity or Eddington ratio, a possible manifestation of AGN feedback associated with accretion disk winds or outflows. This extra source of nongravitational line broadening should be removed when trying to use sigma_g to estimate sigma_*. We show that the mass budget of the narrow-line region can be accounted for by mass loss from evolved stars. The kinematics of the gas, dominated by random motions, largely reflect the velocity field of the hot gas in the bulge. Lastly, we offer a simple explanation for the correlation between line width and line luminosity observed in the narrow-line region of AGNs.Comment: To appear in ApJ, 11 pages, 6 figure

Bulge and Halo Kinematics Across the Hubble Sequence

The correlation between the maximum rotational velocity of the disk (v_m) and the central stellar velocity dispersion of the bulge (sigma) offers insights into the relationship between the halo and the bulge. We have assembled integrated H I line widths and central stellar velocity dispersions to study the v_m-sigma relation for 792 galaxies spanning a broad range of Hubble types. Contrary to earlier studies based on much smaller samples, we find that the v_m-sigma relation exhibits significant intrinsic scatter and that its zeropoint varies systematically with galaxy morphology, bulge-to-disk ratio, and light concentration, as expected from basic dynamical considerations. Nucleated but bulgeless late-type spiral galaxies depart significantly from the v_m-sigma relation. While these results render questionable any attempt to supplant the bulge with the halo as the fundamental determinant of the central black hole mass in galaxies, the observed distribution of v_m/sigma, which depends on both the density profile and kinematic structure of the galaxy, offers a useful constraint on galaxy formation models. With the aid of a near-infrared Tully-Fisher relation, we identify a population of otherwise normal, luminous galaxies that have exceptionally low values of v_m/sigma. We argue that a significant fraction of the H I gas in these kinematically anomalous objects is dynamically unrelaxed, having been acquired externally either through capture from tidal interactions or through cold accretion from the intergalactic medium.Comment: 17 pages. To appear in Ap

Nonstandard Central Engines in Nearby Galaxies

We argue that nearby galaxy nuclei contain massive black holes that are fueled by low radiative efficiency accretion flows.Comment: To appear in Issues in Unification of AGNs, ed. R. Maiolino, A. Marconi, & N. Nagar (San Francisco: ASP), in press. 6 page