QSO Host Research Articles

CO Line Width Differences in Early Universe Molecular Emission-Line Galaxies: Submillimeter Galaxies versus QSO Hosts

We investigate the CO line widths in early universe molecular emission-line galaxies. There is a clear difference in the CO line widths in QSO host galaxies compared to submillimeter galaxies, as first pointed out by Greve et al., with the QSO hosts' line widths typically a factor of 2.3 narrower in velocity. Powerful radio galaxies fall in between. At the same time, there is no major difference between the molecular gas mass distributions of the different galaxy types. We consider possible explanations for the narrower line widths in the QSO hosts and favor an explanation that the QSO hosts are systematically closer to the sky plane than the submillimeter galaxies, QSO = 18°, consistent with the lack of strong obscuration toward the active galactic nucleus. However, we cannot rule out other possible factors, such as different stages in a merger sequence or galaxy mass or size. Only high-resolution imaging of a large sample of sources can address this interesting dichotomy.

Dense Molecular Gas and the Role of Star Formation in the Host Galaxies of Quasi?stellar Objects

New millimeter-wave CO and HCN observations of the host galaxies of infrared-excess Palomar Green quasi-stellar objects (PG QSOs) previously detected in CO are presented. These observations are designed to assess the validity of using the infrared luminosity to estimate star formation rates of luminous AGN by determining the relative significance of dust-heating by young, massive stars and active galactic nuclei (AGN) in QSO hosts and IRAS galaxies with warm, AGN-like infrared colors. The HCN data show the PG QSO host IZw1 and most of the warm IRAS galaxies to have high L_IR / L'_HCN (>1600) relative to the cool IRAS galaxy population for which the median L_IR / L'_HCN ~ 890(+440,-470). If the assumption is made that the infrared emission from cool IRAS galaxies is reprocessed light from embedded star-forming regions, then high values of L_IR / L'_HCN are likely the result of dust heating by the AGN. Further, if the median ratio of L'_HCN / L'_CO ~ 0.06 observed for Seyfert galaxies and IZw1 is applied to the PG QSOs not detected in HCN, then the derived L_IR / L'_HCN correspond to a stellar contribution to the production of L_IR of ~ 7-39%, and star formation rates ~ 2-37 M_sun/yr are derived for the QSO hosts. Alternatively, if the far-infrared is adopted as the star formation component of the total infrared in cool galaxies, the stellar contributions in QSO hosts to their L_FIR are up to 35% higher than the percentages derived for L_IR. This raises the possibility that the L_FIR in several of the PG QSO hosts, including IZw1, could be due entirely to dust heated by young, massive stars. Finally, there is no evidence that the global HCN emission is enhanced relative to CO in galaxies hosting luminous AGN.

VLT adaptive optics imaging of QSO host galaxies and their close environment at z $\mathsf{\sim}$ 2.5: Results from a pilot program

We report on ESO-VLT near-IR adaptive optics imaging of one radio-loud (PKS 0113-283) and two radio quiet (Q 0045-3337 and Q 0101-337) quasars at z > 2. In the first case we are able to resolve the QSO and find that it is hosted by an elliptical of absolute magnitude MK = −27.6. For the other two objects no extended emission has been unambiguously detected. This result, although restricted to a single object, extends up to z = 2.5 the finding that cosmic evolution of radio-loud quasar hosts follows the trend expected for luminous and massive spheroids undergoing passive evolution. For Q 0045-3337 our high resolution images show that it is located 1.2 arcsec from a K = 17.5 foreground disc galaxy, which may act as a gravitational lens, since the QSO most probably lies within the galaxy Einstein radius.

The Qso Hosts I Zw 1 and 3C 48: Prototypes of a Merger-Driven Quasar Evolution?

The Qso Hosts I Zw 1 and 3C 48: Prototypes of a Merger-Driven Quasar Evolution?

Erratum: Chemical abundances in QSO host galaxies and environments from narrow absorption line systems

Erratum: Chemical abundances in QSO host galaxies and environments from narrow absorption line systems

On the Formation and Evolution of QSOs

I had the privilege, many years ago, to be supervised by Alfonso Cavaliere in my Master thesis work. I remember the great patience and enthusiasm with which, in a warm summer day, he presented to me a score of exciting astrophysical problems. We finally determined to study the relationship of QSOs and BL Lacs—then considered rather exotic object—with normal galaxies. In the years I have continued on this line of research, reacting far too slowly to the wealth of new ideas that Alfonso has been continuously injecting in our conversations. As examples I will report two recent results on the chemical abundances of QSO host galaxies and on the space density of high-z QSOs, which are closely related to our shared interest on AGN.

Resolving the Host Galaxy of the Nearby QSO I Zw 1 with Subarcsecond Multitransition Molecular Line Observations

We present the first subkiloparsec (~07 ≈ 850 pc) resolution 12CO(1-0) molecular line observations of the interstellar medium (ISM) in the host galaxy of the QSO I Zw 1. The observations were obtained with the BIMA millimeter interferometer in its compact A configuration. The BIMA data are complemented by new observations of the 12CO(2-1) and 13CO(1-0) lines with the IRAM Plateau de Bure Interferometer (PdBI) at 09 and 21 resolution, respectively. These measurements, which are part of a multiwavelength study of the host galaxy of I Zw 1, are aimed at comparing the ISM properties of a QSO host with those of nearby galaxies, as well as to obtain constraints on galaxy formation/evolution models. Our images of the 12CO(1-0) line emission show a ringlike structure in the circumnuclear molecular gas distribution with an inner radius of about 1.2 kpc. The presence of such a molecular gas ring was predicted from earlier lower angular resolution PdBI 12CO(1-0) observations. A comparison of the BIMA data with IRAM PdBI 12CO(2-1) observations shows variations in the excitation conditions of the molecular gas in the innermost 15 comprising the nuclear region of I Zw 1. The observed properties of the molecular cloud complexes in the disk of the host galaxy suggest that they may be the sites of massive circumnuclear star formation and show no indications of excitation by the active galactic nucleus (AGN). This all indicates that the molecular gas in a QSO host galaxy has properties similar to the gas observed in nearby low-luminosity AGNs.

Gemini Imaging of QSO Host Galaxies atz ∼ 2

We present results of a Gemini adaptive optics (AO) imaging program to investigate the host galaxies of typical QSOs at z ~ 2. Our aim is to study the host galaxies of typical L QSOs at the epoch of peak QSO and star formation activity. The large database of faint QSOs provided by the Two-Degree Field QSO Redshift Survey allows us to select a sample of QSOs at z = 1.75-2.5 that have nearby (<12'' separation) bright stars suitable for use as AO guide stars. We have observed a sample of nine QSOs. The images of these sources have AO-corrected FWHM of between 011 and 025. We use multiple observations of point-spread function (PSF) calibration star pairs to quantify any uncertainty in the PSF. We then factored these uncertainties into our modeling of the QSO plus host galaxy. In only one case did we convincingly detect a host (2QZ J133311.4+001949, at z = 1.93). This host galaxy has K = 18.5 ± 0.2 mag with a half-light radius Re = 055 ± 01 equivalent to ~3L, assuming a simple passively evolving model. From detailed simulations of our host galaxy modeling process, we find that for four of our targets we should be sensitive to host galaxies that are equivalent to ~2L (passively evolved). Our nondetections therefore place tight constraints on the properties of L QSO host galaxies, which can be no brighter (after allowing for passive evolution) than the host galaxies of L active galactic nuclei at low redshift, although the QSOs themselves are a factor of ~50 brighter. This implies that either the fueling efficiency is much greater at high redshift or that more massive black holes are active at high redshift.

Spectrophotometry of Planetary Nebulae in the Bulge of M31

We introduce crowded-field integral field (3D) spectrophotometry as a useful technique for the study of resolved stellar populations in nearby galaxies. The spectroscopy of individual extragalactic stars, which is now feasible with efficient instruments and large telescopes, is confronted with the observational challenge of accurately subtracting the bright, spatially and wavelength-dependent nonuniform background of the underlying galaxy. As a methodological test, we present a pilot study with selected extragalactic planetary nebulae (XPNe) in the bulge of M31, demonstrating how 3D spectroscopy is able to improve the limited accuracy of background subtraction that one would normally obtain with classical slit spectroscopy. It is shown that because of the absence of slit effects, 3D spectroscopy is a most suitable technique for spectrophometry. We present spectra and line intensities for five XPNe in M31, obtained with the MPFS instrument at the Russian 6 m Bolshoi Teleskop Azimutal'nij, INTEGRAL at the William Herschel Telescope , and PMAS at the Calar Alto 3.5 m telescope. The results for two of our targets, for which data are available in the literature, are compared with previously published emission-line intensities. The three remaining PNe have been observed spectroscopically for the first time. One object is shown to be a previously misidentified supernova remnant. Our monochromatic Hα maps are compared with direct Fabry-Perot and narrowband filter images of the bulge of M31, verifying the presence of filamentary emission of the interstellar medium in the vicinity of our objects. We present an example of a flux-calibrated and continuum-subtracted filament spectrum and demonstrate how the interstellar medium component introduces systematic errors in the measurement of faint diagnostic PN emission lines when conventional observing techniques are employed. It is shown how these errors can be eliminated with 3D spectroscopy, using the full two-dimensional spatial information and point-spread function (PSF) fitting techniques. Using 3D spectra of bright standard stars, we demonstrate that the PSF is sampled with high accuracy, providing a centroiding precision at the milliarcsecond level. Crowded-field 3D spectrophotometry and the use of PSF fitting techniques is suggested as the method of choice for a number of similar observational problems, including luminous stars in nearby galaxies, supernovae, QSO host galaxies, gravitationally lensed QSOs, and others.

The environments of hyperluminous infrared galaxies at 0.44 &lt;z&lt; 1.55

We present deep wide-field Ks-band observations of six Hyperluminous Infrared Galaxies (HLIRGs) spanning a redshift range 0.44 = 190 +/- 45 Mpc1.77. The range in environments, and the mean clustering level, are both greater than those seen in local IR-luminous galaxies, from which we infer that the range of galaxy evolution processes driving IR-luminous galaxy evolution at z > 0.5 is greater than locally, and includes mergers between gas-rich spiral galaxies in the field, but also includes encounters in clusters and hierarchical build-up. The similarity in the range of environments and mean clustering amplitude between our sample and QSOs over a similar redshift range is consistent with the interpretation where evolutionary connections between IR-luminous galaxies and QSOs are stronger at z > 0.5 than locally, and that, at these redshifts, the processes that drive QSO evolution are similar to those that drive IR-luminous galaxy evolution. From comparison of the HLIRG and QSO host galaxies we further postulate that a larger fraction of IR-luminous galaxies pass through an optical QSO stage at z > 0.5 than locally.

Integral field spectroscopy of QSO host galaxies

AbstractWe describe a project to study the state of the ISM in ∼20 low redshift (z &lt; 0.3) QSO host galaxies observed with the PMAS integral field spectrograph. We describe the development of the method to access the stellar and gas components of the spectrum without the strong nuclear emission, in order to access the host galaxy properties in the central region. It shows that integral field spectroscopy promises to be very efficient in studying the gas distribution and its velocity field, and also the spatially resolved stellar population in the host galaxies of luminous AGN. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Double Nuclei and “TDGs”: Colliding or Activity of Nucleus Monster?

It is known that among active galaxies (AG) with strong emission lines (UV-galaxies, Sy 1 and Sy2, Markarian and Kazarian galaxies, Radio-galaxies, QSO's host galaxies and so on) there are large per cent of objects with double and multiple nucleus. The common sizes and volumes of these nuclei are on the order of a few hundred parsecs or kilo-parsecs. In fact these are not double galaxies or clusters of galaxies as many of astronomers believe, but just the complicated nucleus of AG. The problem is:what are the nature and the birth of these objects?There are in fact two basic suppositions in the subject: (a) The complicated nuclei are the result of merging or colliding of two or more galaxies, or: (b) They are the results of nuclear activity. The results of detailed spectroscopic observations of a number of ”tidal galaxies”, carried out with the 5m Palomar telescope, 2.6m telescope of Ambartsumian Byurakan astrophysical observatory (multi-pupil spectroscopy with Tiger receiver) and 6m telescope of Special Astrophysical observatory of Russia are presented. It is shown that in many cases the ”tidal dwarf galaxies ”(or actually complicated nucleus) are the result of galactic nuclear activity.

Dust emission from the most distant quasars

We report observations of three SDSS QSOs at 250 GHz (1.2 mm) using the 117-channel Max-Planck Millimeter Bolometer (MAMBO-2) array at the IRAM 30-meter telescope. J1148+5251 () and J1048+4637 () were detected with 250 GHz flux densities of and , respectively. J1630+4012 () was not detected with a upper limit of 1.8 mJy. Upper flux density limits from VLA observations at 43 GHz for J1148+5251 and J1048+4637 imply steeply rising spectra, indicative of thermal infrared emission from warm dust. The far-infrared luminosities are estimated to be ≈, and the dust masses ≈, assuming Galactic dust properties. The presence of large amounts of dust in the highest redshift QSOs indicates that dust formation must be rapid during the early evolution of QSO host galaxies. Dust absorption may hinder the escape of ionizing photons which reionize the intergalactic medium at this early epoch.

I Zw 1: Decomposition of the nearby QSO host

The paper presents an analysis of the nearby QSO host I Zw 1 based on new J-band imaging data, obtained with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO). As one of the best-studied QSOs with exceptional properties lying between those of QSOs, narrow-line Seyfert 1s, and ultraluminous infrared galaxies , I Zw 1 is a prime candidate for a detailed case study of a QSO host. With its high angular resolution and sensitivity, the new J-ba nd image provides strong evidence for an interaction between I Zw 1 and the western companion galaxy. We present a procedure for subtracting the QSO nucleus from the I Zw 1 image to obtain an undisturbed view on the underlying host galaxy. Based on the derived surface brightness profile and the gas rotatio n curve, the host is classified as a high-surface-brightness Freeman type I galaxy with a central disk surface brightness signific antly larger than that of normal spirals. The surface-brigh tness profile is decomposed into a Plummer bulge and a Kuzmin disk wi th similar luminosities and a bulge-to-disk scale length ra tio of 0.29, comparable to that of nearby spiral hosts with active galactic nuclei (AGN). Different models for the decomposition of the gas rotation curve are discussed. The resulting J-band mass-to-light ratio (M/L) of (0.7± 0.4) M⊙/L⊙ for the disk component suggests a mean solar-type stellar population with a tendency towards young stars. The bulge exhibits a lower M/L of (0.4± 0.2) M⊙/L⊙, which supports previous findings of enhanced starburst act ivity in the nuclear and circumnuclear region.

Protoquasars: Physical States and Observable Properties

Based on the radiation hydrodynamic model for black hole (BH) growth and incorporating the chemical evolution of the early-type host galaxy, we construct the coevolution model of the quasar (QSO) BH and host galaxy. As a result, it is found that after a galactic wind epoch, the luminosity is shifted from the host-dominant phase to the active galactic nucleus-dominant phase (QSO phase) in the timescale of a few 108 yr. The former phase corresponds to the early stage of a growing BH and can be regarded as a "proto-QSO" phase. It has observable characteristic properties as follows: (1) The broad emission lines are narrower than those of ordinary QSOs and are typically less than 1500 km s-1. (2) The BH-to-bulge mass ratio, MBH/Mbulge, is in the range of 10-5.3 to 10-3.9. (3) Host galaxies are bluer than QSO hosts, by about 0.5 mag in the colors B-V at the rest bands and V-K at the observed bands, with assumed galaxy formation redshifts of zf = 3-5. (4) The metallicity of gas in the galactic nuclei is ~8 Z☉ and that of stars weighted by the host luminosity is ~3 Z☉. (5) The central massive BH (≃107 M☉) is surrounded by a massive dusty disk (>108 M☉), which may obscure the nucleus in the edge-on view and make a type 2 nucleus. By comparing these predictions with recent observations, radio galaxies are a possible candidate for proto-QSOs. Also, it is anticipated that the proto-QSO phase is preceded by an optically thick phase, which may correspond to ultraluminous infrared galaxies (ULIRGs). In this phase, MBH/Mbulge is predicted to be much less than 10-3 and to grow with metallicity. Moreover, as precursors of ULIRGs, optically thin star-forming galaxies are predicted. These may be in the assembly phase of Lyman break galaxies (LBGs) or Lyα emitters.

I Zw 1: Decomposition of the Nearby QSO Host

The paper presents an analysis of the nearby QSO host I Zw 1 based on new J-band imaging data, obtained with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO). As one of the best-studied QSOs with exceptional properties lying between those of QSOs, narrow-line Seyfert 1s, and ultraluminous infrared galaxies, I Zw 1 is a prime candidate for a detailed case study of a QSO host. With its high angular resolution and sensitivity, the new J-band image provides strong evidence for an interaction between I Zw 1 and the western companion galaxy. We present a procedure for subtracting the QSO nucleus from the I Zw 1 image to obtain an undisturbed view on the underlying host galaxy. Based on the derived surface brightness profile and the gas rotation curve, the host is classified as a high-surface-brightness Freeman type I galaxy with a central disk surface brightness significantly larger than that of normal spirals. The surface-brightness profile is decomposed into a Plummer bulge and a Kuzmin disk with similar luminosities and a bulge-to-disk scale length ratio of 0.29, comparable to that of nearby spiral hosts with active galactic nuclei (AGN). Different models for the decomposition of the gas rotation curve are discussed. The resulting J-band mass-to-light ratio (M/L) of (0.7+/-0.4) M_sun/L_sun for the disk component suggests a mean solar-type stellar population with a tendency towards young stars. The bulge exhibits a lower M/L of 0.4+/-0.2 M_sun/L_sun, which supports previous findings of enhanced starburst activity in the nuclear and circumnuclear region.

The Luminosity Function of QSO Host Galaxies

We present some results from our HST archival image study of 71 QSO host galaxies. The objects are selected to have z less than or equal to 0.46 and total absolute magnitude M(sub v) less than or equal to -23 in our adopted cosmology (H(sub 0) = 50 kilometers per second Mpc(sup-1), q(sub 0) = 0.5, lambda = 0)). The aim of this initial study is to investigate the composition of the sample with respect to host morphology and radio loudness, as well as derive the QSO host galaxy luminosity function. We have analyzed available WFPC2 images in R or I band (U in one case), using a uniform set of procedures. The host galaxies span a narrow range of luminosities and are exceptionally bright, much more so than normal galaxies, usually L greater than L*(sub v). The QSOs are almost equally divided among three subclasses: radio-loud QSOs with elliptical hosts, radio-quiet QSOs with elliptical hosts, and radio-quiet QSOs with spiral hosts. Radio-loud QSOs with spiral hosts are extremely rare. Using a weighting procedure, we derive the combined luminosity function of QSO host galaxies. We find that the luminosity function of QSO hosts differs in shape from that of normal galaxies but that they coincide at the highest luminosities. The ratio of the number of quasar hosts to the number of normal galaxies at a luminosity L*(sub v) is R = (Lv/11.48L*(sub v))(sup 2.46), where L*(sub v) corresponds to M*(sub v)= -22.35, and a QSO is defined to be an object with total nuclear plus host light M(sub v) less than or equal to -23. This ratio can be interpreted as the probability that a galaxy with luminosity L(sub V) will host a QSO at redshift z approximately equal to 0.26.

An HI Search for the Host Galaxies of 27 Radio-loud AGN at z ∼ 2.3

This project was inspired by optical and IR imaging suggesting that, while most QSO hosts at high z are too faint to detect, radio-loud quasars are hosted by exceptionally luminous galaxies. Thus, a search was undertaken for HI absorption against the continuum emission of strong radio emitters whose redshifts (z ∼ 2.3) bring their HI line into the 430-MHz Arecibo passband2. The aim was to detect, or set useful limits, on the HI in the hosts, say in dust lanes, introduced by mergers, or situated in obscuring circumnuclear tori. At Arecibo there is a choice of, a) the 430-MHz line-feed system, or b) the new 430-MHz Gregorian-dome feed. In practice, most of the data were taken with the Gregorian system, although some line-feed data were also acquired. This represents the first Arecibo line spectroscopy using the 430-MHz Gregorian receiver.

Atomic Hydrogen Gas Images of QSO Host Galaxies

We present the first neutral atomic hydrogen (HI) gas images of QSO host galaxies. The results come from our ongoing survey of all twenty-three QSOs at redshifts z &lt; 0.07 visible from the VLA. Our images show tidal interactions in all of the QSO host galaxies detected in HI, even when no such interactions are clearly visible in the optical. The results are not consistent with the suggestion by Sanders et al. (1988a, 1988b) that ultraluminous infrared galaxies, the vast majority of which are later-stage mergers, are the parent population of a significant fraction of radio-quiet QSOs. Instead, our results suggest that QSOs reside in a wide variety of interacting environments.

Surveys of High-Redshift QSO Hosts

AbstractRecent investigations of high-redshift QSO morphology are reviewed and compared. The PSF-removal is difficult and results are given in several different forms. The reliability of results from HST and ground-based AO are compared, and several caveats to conventional wisdom are given.