QSO Host Research Articles

FORMATION OF HIGH-REDSHIFT (z>6) QUASARS DRIVEN BY NUCLEAR STARBURSTS

Based on the physical model of a supermassive black hole (SMBH) growth via gas accretion in a circumnuclear disk (CND) proposed by Kawakatu & Wada (2008), we describe the formation of high-$z$ ($z > 6$) quasars (QSOs) whose BH masses are M_{BH}> 10^{9} M_{\odot}. We derive the necessary conditions to form QSOs at z > 6 by only gas accretion: (i) A large mass supply with M_{sup} > 10^{10}M_{\odot} from host galaxies to CNDs, because the final BH mass is only 1-10% of the total supplied mass from QSO hosts. (ii) High star formation efficiency for a rapid BH growth. We also find that if the BH growth is limited by the Eddington accretion, the final BH mass is greatly suppressed. Thus, the super-Eddington growth is required for the QSO formation. The evolution of the QSO luminosity depends on the redshift z_{i} at which accretion onto a seed BH is initiated. In other words, the brighter QSOs at z >6 favor the late growth of SMBHs (i.e., z_{i}=10) rather than early growth (i.e., z_{i}=30). Moreover, we predict the observable properties and the evolution of QSOs at z >6. In a QSO phase, there should exist a stellar rich massive CND, whose gas mass is about 10% of the dynamical mass inside 0.1-1 kpc}. On the other hand, in a phase where the BH grows (i.e., a proto-QSO phase), the proto-QSO has a gas rich massive CNDs whose gas mass is comparable to the dynamical mass (abridged).

Integral Field Spectroscopy of z ~ 0.1 QSO Host Galaxies

We observed a volume-limited sample of 19 luminous type 1 QSO host galaxies at MV ~ −23 mag and redshift 0.06 < z < 0.2 (Jahnke et al. 2004) using the VLT/VIMOS Integral Field Spectrograph. After removal of the QSO contribution (using the method of Husemann et al. 2008), we construct 2D intensity maps and gas velocity fields of the host galaxies in the Hα and [O iii] emission lines. Two representative cases are shown in Figure 1.

No Evolution in the MBH–M*,total Relation Over the Last 9 Gyrs

We investigate 10 QSO host galaxies at 1<z<2 in the COSMOS field (Scoville et al. 2007), observed with the HST in both ACS/WFC I-band and NICMOS/NIC3 H-band. We find that our galaxies with mean z = 1.4 follow the local MBH–Mbulge relation exactly – however, not with an explicit bulge mass, but with their total stellar mass.

The Power of Deconvolution for Study of QSO Host Galaxies

AbstractThe major challenge in studying QSO host galaxies is to remove the QSO contribution, which often outshines the whole system. Our group has acquired the technical ability to handle such data, for images and slit spectroscopy, as well as integral field spectroscopy. We review here the major techniques developed by our team, and their latest applications. We are open for collaboration with other teams to spread the use of these powerful techniques.

COMMENT ON THE BLACK HOLE RECOIL CANDIDATE QUASAR SDSS J092712.65+294344.0

SDSS J092712.65+294344.0 has been proposed as a candidate for a supermassive black hole (~10^8.8 solar masses) ejected at high speed from the host galactic nucleus by gravitational radiation recoil, or alternatively for a supermassive black hole binary. This is based on a blueshift of 2650 km/s of the broad emission lines ("b-system") relative to the narrow emission lines ("r-system") presumed to reflect the galaxy velocity. New observations with the Hobby-Eberly Telescope (HET) confirm the essential features of the spectrum. We note a third redshift system, characterized by weak, narrow emission lines of [O III] and [O II] at an intermediate velocity 900 km/s redward of the broad line velocity ("i-system"). A composite spectrum of SDSS QSOs similar to J0927 illustrates the feasibility of detecting the calcium K absorption line in spectra of sufficient quality. The i-system may represent the QSO host galaxy or a companion. Photoionization requires the black hole to be ~3 kpc from the r-system emitting gas, implying that we are observing the system only 10^6 yr after the recoil event and contributing to the low probability of observing such a system. The HET observations give an upper limit of 10 km/s per year on the rate of change of the velocity difference between the r- and b-systems, constraining the orbital phase in the binary model. These considerations and the presence of a cluster of galaxies apparently containing J0927 favor the idea that this system represents a superposition of two AGN.

ENVIRONMENTS OF QSOs AT REDSHIFT 0.9-1.3

We analyze new deep g- and i-band imaging of 16 QSOs in the redshift range 0.9-1.3 with the Canada-France-Hawaii Telescope. The principal points of interest are the symmetry and signs of tidal effects in the QSO hosts and nearby (companion) galaxies. The sample measures are compared with similar measures on randomly selected field galaxy samples. Asymmetry measures are made for all objects to g ~ 22, and magnitudes of all galaxies 2 mag fainter. The QSOs are found in denser environments than the field, and are somewhat offset from the centroid of their surrounding galaxies. The QSO hosts appear more disturbed than other galaxies. While the QSO companions and field galaxies have the same average asymmetry, the distribution of asymmetry values is different. QSO companions within 15'' are fainter than average field galaxies. We discuss scenarios that are consistent with these and other measured quantities.

The 2dF-SDSS LRG and QSO Survey: the spectroscopic QSO catalogue

We present the final spectroscopic QSO catalogue from the 2dF-SDSS LRG (luminous red galaxy) and QSO (2SLAQ) survey. This is a deep, 18 < g < 21.85 (extinction corrected), sample aimed at probing in detail the faint end of the broad line active galactic nuclei luminosity distribution at z 2.6. The candidate QSOs were selected from SDSS photometry and observed spectroscopically with the 2dF spectrograph on the Anglo-Australian Telescope. This sample covers an area of 191.9 deg 2 and contains new spectra of 16 326 objects, of which 8764 are QSOs and 7623 are newly discovered [the remainder were previously identified by the 2dF QSO Redshift Survey (2QZ) and SDSS]. The full QSO sample (including objects previously observed in the SDSS and 2QZ surveys) contains 12 702 QSOs. The new 2SLAQ spectroscopic data set also contains 2343 Galactic stars, including 362 white dwarfs, and 2924 narrow emission-line galaxies with a median redshift of z = 0.22. We present detailed completeness estimates for the survey, based on modelling of QSO colours, including host-galaxy contributions. This calculation shows that at g � 21.85 QSO colours are significantly affected by the presence of a host galaxy up to redshift z ∼ 1i n the SDSS ugriz bands. In particular, we see a significant reddening of the objects in g − i towards the fainter g-band magnitudes. This reddening is consistent with the QSO host galaxies being dominated by a stellar population of age at least 2–3 Gyr.

High-excitation molecular gas in local luminous AGN hosts

We used the mm/sub-mm receivers on the James Clerk Maxwell Telescope (JCMT) to observe the CO J=3--2, 2--1 lines in five local, optically powerful AGN and the J=4--3 line in 3C 293 (a powerful radio galaxy). Luminous CO J=3--2 emission and high CO (3--2)/(1--0) intensity ratios are found in all objects, indicating highly excited molecular gas. In 3C 293 an exceptionally bright CO J=4--3 line is found which cannot be easily explained given its quiescent star-forming environment and low AGN X-ray luminosity. In this object shocks emanating from a well-known interaction of a powerful jet with a dense ISM may be responsible for the high excitation of its molecular gas on galaxy-wide scales. Star formation can readily account for the gas excitation in the rest of the objects, although high X-ray AGN luminosities can also contribute significantly in two cases. Measuring and eventually imaging CO line ratios in local luminous QSO hosts can be done by a partially completed ALMA during its early phases of commissioning, promising a sensitive probe of starburst versus AGN activity in obscured environments at high linear resolutions.

HOST GALAXIES OF LUMINOUS QUASARS: STRUCTURAL PROPERTIES AND THE FUNDAMENTAL PLANE

We present stellar velocity dispersion measurements in the host galaxies of ten luminous quasars (MV < −23) using the Ca H&K lines in off-nuclear spectra. We combine these data with effective radii and magnitudes from the literature to place the host galaxies on the fundamental plane (FP) where their properties are compared with other types of galaxies. We find that the radio-loud (RL) QSO hosts have similar properties to massive elliptical galaxies, while the radio-quiet (RQ) hosts are more similar to intermediate-mass galaxies. The RL hosts lie at the upper extreme of the FP due to their large velocity dispersions (〈σ*〉 = 321 km s−1), low surface brightness (〈μe(r)〉 = 20.8 mag arcsec−2), and large effective radii (〈Re〉 = 11.4 kpc), and have 〈M*〉 = 1.5 × 1012 M☉ and 〈M/L〉 = 12.4. In contrast, properties of the RQ hosts are 〈σ*〉 = 241 km s−1, 〈M*〉 = 4.4 × 1011 M☉, and M/L ∼ 5.3. The distinction between these galaxies occurs at σ*∼ 300 km s−1, Re∼ 6 kpc, and corresponding M* ∼ 5.9 ± 3.5 × 1011 M☉. Our data support previous results that Palomar-Green QSOs are related to gas-rich galaxy mergers that form intermediate-mass galaxies, while RL QSOs reside in massive early-type galaxies, most of which also show signs of recent mergers or interactions. Previous authors have drawn these conclusions by using estimates of the black hole mass and inferring host galaxy properties from that, while here we have relied purely on directly measured host galaxy properties.

Adaptive optics: Observations and prospects for studies of active Galactic Nuclei

These lectures take a look at how observations with adaptive optics (AO) are beginning to influence our understanding of active galactic nuclei (AGN). By focussing on a few specific topics, the aim is to highlight the different ways in which enhanced spatial resolution from AO can aid the scientific analysis of AGN data. After presenting some background about how AO works, I will describe a few recent observations made with AO of QSO host galaxies, the Galactic Center, and nearby AGN, and show how they have contributed to our knowledge of these enigmatic objects.

Constraints on the correlation between QSO luminosity and host halo mass from high-redshift quasar clustering

Recent measurements of high-redshift quasar (QSO) clustering from the Sloan Digital Sky Survey indicate that QSOs at z∼ 4 have a bias 〈b〉≃ 14. We find that this extremely high clustering amplitude, combined with the corresponding space density, constrains the dispersion in the L–Mh relation to be less than 50 per cent at 99 per cent confidence for the most conservative case of a 100 per cent duty cycle. This upper limit to the intrinsic dispersion provides as strong a constraint as current upper limits to the intrinsic dispersion in the local MBH–σ relation and the ratio of bolometric to Eddington luminosity of luminous QSOs.

Evidence for Merger Remnants in Early‐Type Host Galaxies of Low‐Redshift QSOs1

We present results from a pilot HST ACS deep imaging study in broadband 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 ∼ 3reff 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.

Studying the first galaxies with ALMA

We discuss observations of the first galaxies, within cosmic reionization, at centimeter and millimeter wavelengths. We present a summary of current observations of the host galaxies of the most distant QSOs (z∼6). These observations reveal the gas, dust, and star formation in the host galaxies on kpc-scales. These data imply an enriched ISM in the QSO host galaxies within 1 Gyr of the big bang, and are consistent with models of coeval supermassive black hole and spheroidal galaxy formation in major mergers at high redshift. Current instruments are limited to studying truly pathologic objects at these redshifts, meaning hyper-luminous infrared galaxies (L FIR ∼1013 L ⊙). ALMA will provide the one to two orders of magnitude improvement in millimeter astronomy required to study normal star forming galaxies (i.e. Ly-α emitters) at z∼6. ALMA will reveal, at sub-kpc spatial resolution, the thermal gas and dust—the fundamental fuel for star formation—in galaxies into cosmic reionization.

Molecular gas in QSO host galaxies at z &gt; 5

We present observations with the IRAM Plateau de Bure Interferometer of three QSOs at z > 5 aimed at detecting molecular gas in their host galaxies as traced by CO transitions. CO (5-4) is detected in SDSS J033829.31+002156.3 at z = 5.0267, placing it amongst the most distant sources detected in CO. The CO emission is unresolved with a beam size of ∼1, implying that the molecular gas is contained within a compact region, less than ∼3 kpc in radius. We infer an upper limit on the dynamical mass of the CO emitting region of ∼3× 1010 M ⊙ /sin(i) 2 . The comparison with the Black Hole mass inferred from near-IR data suggests that the BH-to-bulge mass ratio in this galaxy is significantly higher than in local galaxies. From the CO luminosity we infer a mass reservoir of molecular gas as high as M(H 2 ) = 2.2 x 1010 M ⊙ , implying that the molecular gas accounts for a significant fraction of the dynamical mass. When compared to the star formation rate derived from the far-IR luminosity, we infer a very short gas exhaustion timescale (∼10 7 years), comparable to the dynamical timescale. CO is not detected in the other two QSOs (SDSS J083643.85+005453.3 and SDSS J163033.90+401209.6) and upper limits are given for their molecular gas content. When combined with CO observations of other type 1 AGNs, spanning a wide redshift range (0 5) the CO luminosity appears to saturate. We discuss the implications of these findings in terms of black hole-galaxy co-evolution.

Searching for mergers in early-type QSO host galaxies and a control sample of inactive ellipticals

AbstractWe present very deep HST/ACS images of five QSO host galaxies, classified as undisturbed ellipticals in earlier studies. For four of the five objects, our images reveal strong signs of interaction such as tidal tails, shells, and other fine structure, suggesting that a large fraction of QSO host galaxies may have experienced a relatively recent merger event. Our preliminary results for a control sample of inactive elliptical galaxies do not reveal comparable fine structure.

Molecular gas in nearby low-luminosity QSO host galaxies

Aims. This paper addresses the global molecular gas properties of a representative sample of galaxies hosting low-luminosity quasistellar objects. An abundant supply of gas is necessary to fuel both the active galactic nucleus and any circum-nuclear starburst activity of QSOs. The connection between ultraluminous infrared galaxies and the host properties of QSOs is still subject to a controversial debate. Nearby low-luminosity QSOs are ideally suited to study the properties of their host galaxies because of their higher frequency of occurrence compared to high-luminosity QSOs in the same comoving volume and because of their small cosmological distance. Methods. We selected a sample of nearby low-luminosity QSO host galaxies that is free of infrared excess biases. All objects are drawn from the Hamburg-ESO survey for bright UV-excess QSOs, have δ> −30 ◦ and redshifts that do not exceed z = 0.06. The IRAM 30 m telescope was used to measure the 12 CO(1−0) and 12 CO(2−1) transition in parallel. Results. 27 out of 39 galaxies in the sample have been detected. The molecular gas masses of the detected sources range from

Highly-excited CO emission in APM 08279+5255 atz = 3.9

We report the detection of the CO 4–3, 6–5, 9–8, 10–9, and 11–10 lines in the Broad Absorption Line quasar APM 08279+5255 at using the IRAM 30 m telescope. We also present IRAM PdBI high spatial resolution observations of the CO 4–3 and 9–8 lines, and of the 1.4 mm dust radiation as well as an improved spectrum of the HCN(5–4) line. Unlike CO in other QSO host galaxies, the CO line SED of APM 08279+5255 rises up to the CO(10–9) transition. The line fluxes in the CO ladder and the dust continuum fluxes are best fit by a two component model, a “cold” component at ~ K with a high density of n(H2) = 1105 cm-3, and a “warm”, ~ K component with a density of 1104 cm-3. We show that IR pumping via the 14 bending mode of HCN is the most likely channel for the HCN excitation. From our models we find, that the CO(1–0) emission is dominated by the dense gas component which implies that the CO conversion factor is higher than usually assumed for high-z galaxies with 5 (K km s-1 pc2)-1. Using brightness temperature arguments, the results from our high-resolution mapping, and lens models from the literature, we argue that the molecular lines and the dust continuum emission arise from a very compact (r ≈ 100-300 pc), highly gravitationally magnified () region surrounding the central AGN. Part of the difference relative to other high-z QSOs may therefore be due to the configuration of the gravitational lens, which gives us a high-magnification zoom right into the central 200-pc radius of APM 08279+5255 where IR pumping plays a significant role for the excitation of the molecular lines.

Near‐Infrared Adaptive Optics Imaging of QSO Host Galaxies

We report near-infrared (primarily H band) adaptive optics (AO) imaging with the Gemini-N and Subaru Telescopes, of a representative sample of 32 nearby (z < 0.3) QSOs selected from the Palomar-Green (PG) Bright Quasar Survey (BQS), in order to investigate the properties of the host galaxies. Two-dimensional modeling and visual inspection of the images shows that ~36% of the hosts are ellipticals, ~39% contain a prominent disk component, and ~25% are of undetermined type. Thirty percent show obvious signs of disturbance. The mean MH(host) = -24.82 (2.1L), with a range -23.5 to -26.5 (~0.63L to 10L). At <L, all hosts have a dominant disk component, while at >2L most are ellipticals. "Disturbed" hosts are found at all MH(host), while "strongly disturbed" hosts appear to favor the more luminous hosts. Hosts with prominent disks have less luminous QSOs, while the most luminous QSOs are almost exclusively in ellipticals or in mergers (which presumably shortly will be ellipticals). At z < 0.13, where our sample is complete at B band, we find no clear correlation between MB(QSO) and MH(host). However, at z > 0.15, the more luminous QSOs (MB < -24.7), and four of five of the radio-loud QSOs, have the most luminous H-band hosts (>7L), most of which are ellipticals. Finally, we find a strong correlation between the "infrared excess," LIR/LBB, of QSOs with host type and degree of disturbance. Disturbed and strongly disturbed hosts and hosts with dominant disks have LIR/LBB twice that of nondisturbed and elliptical hosts, respectively. QSOs with disturbed and strongly disturbed hosts are also found to have morphologies and mid/far-infrared colors that are similar to what is found for "warm" ultraluminous infrared galaxies, providing further evidence for a possible evolutionary connection between both classes of objects.

Search for dense molecular gas in two QSO host galaxies

Context. The HCN(1-0) rotational line transition traces the dense (n H2 > 10 4 cm -3 ) fraction of the molecular gas typically located in starforming (SF) regions. In addition, an abnormally high HCN/CO line ratio close to AGNs may indicate then conditions of an X-ray-dominated region. Observed correlations between the CO-, HCN-, and FIR luminosities in nearby non-active, starburst, and low-luminosity active galaxies represent the physical connection between star formation and molecular gas as its fuel. HCN(1-0) has hardly been investigated in nearby high-luminosity AGN within this context. Aims. The aim of this study is to compare the HCN luminosity with published CO and IR luminosities to investigate the role of SF in the observed QSO host galaxies. Methods. We used the IRAM 30 m for the first time to search for the HCN(1-0) transition in two standard QSO host galaxies at z ∼ 0.1. Results. Our upper limits on L HCN agree with the known correlations and do not show strong excess abundance or excitation of the HCN due to the luminous active quasar nucleus. The starburst origin of the far-infrared luminosity in the observed QSO hosts cannot be proven unambiguously by the upper limits. We found that the IR/FIR ratio indicates independently of L IR if a significant amount of AGN heated dust is present.

QSO Absorption Lines from QSO s

We present the results of a search for metal absorption lines in the spectra of background QSOs whose sight lines pass close to foreground QSOs. We detect Mg II λλ2796, 2803 absorption in Sloan Digital Sky Survey (SDSS) spectra of four z > 1.5 QSOs whose lines of sight pass within 26-98 h kpc of lower redshift (z ≃ 0.5-1.5) QSOs. The 100% detection rate (four out of four pairs) of Mg II in the background QSOs is clearly at odds with the incidence of associated zabs ≃ zem systems—absorbers that exist toward only a few percent of QSOs. Although the quality of our foreground QSO spectra is not as high as the SDSS data, absorption seen toward one of the background QSOs clearly does not show up at the same strength in the spectrum of the corresponding foreground QSO. This implies that the absorbing gas is distributed inhomogeneously around the QSO, presumably as a direct consequence of the anisotropic emission from the central active galactic nucleus. We discuss possible origins for the Mg II lines, including absorption by gas from the foreground QSO host galaxy, companion galaxies fueling the QSO through gravitational interactions, and tidal debris left by galaxy mergers or interactions that initiated the QSO activity. No single explanation is entirely satisfactory, and we may well be seeing a mixture of phenomena.