Holes In Spiral Galaxies Research Articles

The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies. III. The Link to the M •–M * Correlation

We continue to explore the relationship between the total number of globular clusters (GCs), N GC, and the central black hole mass, M •, in spiral galaxies. We present here results for the Sab galaxies NGC 3368, NGC 4736 (M94), and NGC 4826 (M64), and the Sm galaxy NGC 4395. The GC candidate selection is based on the (u* – ) versus ( – K s ) color–color diagram, and -band shape parameters. We determine the M • versus N GC correlation for these spirals, plus NGC 4258, NGC 253, M104, M81, M31, and the Milky Way. We also redetermine the correlation for the elliptical sample in Harris et al., with updated galaxy types from Sahu et al. Additionally, we derive the total stellar galaxy mass, M *, from its two-slope correlation with N GC, and fit M • versus M * for both spirals and ellipticals. We obtain log M • ∝ (1.01 ± 0.13) log N GC for ellipticals, and log M • ∝ (1.64 ± 0.24) log N GC for late-type galaxies (LTGs). The linear M • versus N GC correlation in ellipticals could be due to statistical convergence through mergers, unlike the much steeper correlation for LTGs. However, in the M • versus total stellar mass (M *) parameter space, with M * derived from its correlation with N GC, M • ∝ (1.48 ± 0.18) log M * for ellipticals, and M • ∝ (1.21 ± 0.16) log M * for LTGs. The observed agreement between ellipticals and LTGs in this parameter space may imply that black holes and galaxies coevolve through calm accretion, active galactic nuclei feedback, and other secular processes.

Spectacular 240 kpc double-sided relativistic jets in a spiral-hosted narrow-line Seyfert 1 galaxy

Narrow-line Seyfert 1 (NLS1) galaxies are a peculiar sub-class of active galactic nuclei (AGNe). They have demonstrated that the presence of relativistic jets in an AGN is not strictly related to its radio-loudness, the black hole mass, or their host galaxy type. Here, we present a remarkable example of a radio-quiet NLS1, 6dFGS gJ035432.8−134008 (J0354−1340). In ourKarl G. JanskyVery Large Array observations at 5.5 GHz, the source shows a bright core with a flat spectral index and extended emission corresponding to very elongated jets. These are the largest double-sided radio jets found to date in an NLS1, with a de-projected linear size of almost 250 kpc. We also analysed near-infrared and optical images obtained by theMagellan Baadeand the European Southern Observatory New Technology Telescope. By means of photometric decomposition and colour maps, we determined that J0354−1340 is hosted by a spiral or disc-like galaxy. Fully evolved relativistic jets have traditionally been associated with high-mass elliptical galaxies hosting the most massive black holes. Instead, our results confirm that powerful jets can also be launched and sustained by less massive black holes in spiral galaxies, implying that the launching of the jets is governed by factors other than those previously believed to be at play.

What Governs Lorentz Factors of Jet Components in Blazars?

We use a sample of radio-loud Active Galactic Nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. Recent investigations suggested that the most super-massive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies. The correlation between black hole mass and bulk Lorentz factor of the jet components found in this work implies that the motion velocity of the jet components is probably governed by the black hole spin. The faster moving jets are magnetically accelerated by the magnetic fields threading the horizon of more rapidly rotating black holes.

WHAT GOVERNS THE BULK VELOCITY OF THE JET COMPONENTS IN ACTIVE GALACTIC NUCLEI?

We use a sample of radio-loud active galactic nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. Based on the K\"{o}nigl's inhomogeneous jet model, the jet parameters, such as the bulk motion Lorentz factor, magnetic field strength, and electron density in the jet, can be estimated with the very long-baseline interferometry and X-ray data. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. The massive black holes will be spun up through accretion, as the black holes acquire mass and angular momentum simultaneously through accretion. Recent investigation indeed suggested that most supermassive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies, where random, small accretion episodes (e.g., tidally disrupted stars, accretion of molecular clouds) might have played a more important role. If this is true, the correlation between black hole mass and the bulk Lorentz factor of the jet components found in this work implies that the motion velocity of the jet components is probably governed by the black hole spin. No correlation is found between the magnetic field strength at $10R_{\rm S}$ ($R_{\rm S}=2GM/c^2$ is the Schwarzschild radius) in the jets and the bulk Lorentz factor of the jet components for this sample. This is consistent with the black hole spin scenario, i.e., the faster moving jets are magnetically accelerated by the magnetic fields threading the horizon of more rapidly rotating black holes. The results imply that the Blandford-Znajek (BZ) mechanism may dominate over the Blandford-Payne (BP) mechanism for the jet acceleration at least in these radio-loud AGNs.

Black Hole Spin and Galactic Morphology

We investigate the conjecture by Sikora, Stawarz, and Lasota that the observed active galactic nuclei (AGNs) radio loudness bimodality can be explained by the morphology-related bimodality of black hole spin distribution in the centers of galaxies: central black holes (BHs) in giant elliptical galaxies may have (on average) much larger spins than black holes in spiral/disk galaxies. We study how accretion from a warped disk influences the evolution of black hole spins and conclude that within the cosmological framework, where the most massive BHs have grown in mass via merger-driven accretion, one indeed expects most supermassive black holes in elliptical galaxies to have on average higher spin than black holes in spiral galaxies, where random, small accretion episodes (e.g., tidally disrupted stars, accretion of molecular clouds) might have played a more important role.

Supermassive black holes in the Sbc spiral galaxies NGC 3310, NGC 4303 and NGC 4258

We have undertaken an HST Space Telescope Imaging Spectrograph survey of 54 late type spiral galaxies to study the scaling relations between black holes and their host spheroids at the low mass end. Our aim is to measure black hole masses or to set upper limits for a sizeable sample of spiral galaxies. In this paper we present new Space Telescope Imaging Spectrograph (STIS) observations of three spiral galaxies, NGC 4303, NGC 3310 and NGC 4258. The bright optical emission lines Hα λ , [NII] λλ and [SII] λλ were used to study the kinematics of the ionized gas in the nuclear region of each galaxy with a ~ spatial resolution. Our STIS data for NGC 4258 were analyzed in conjunction with archival ones to compare the gas kinematical estimate of the black hole mass with the accurate value from H2O-maser observations. In NGC 3310, the observed gas kinematics is well matched by a circularly rotating disk model but we are only able to set an upper limit to the BH mass which, taking into account the allowed disk inclinations, varies in the range – at the 95% confidence level. In NGC 4303 the kinematical data require the presence of a BH with mass (for a disk inclination deg) but the weak agreement between data and disk model does not allow us to consider this measurement completely reliable. If the allowed inclination values are taken into account, MBH varies in the range – at the 95% confidence level. In NGC 4258, the observed kinematics require the presence of a black hole with ( deg) and, taking into account reasonable limits for the inclination, MBH is in the range – at the 95% confidence level. This result is in good agreement with the published value , derived from H2O-maser observations. As in the case of NGC 4303, the agreement between observed and model kinematics is not strong but this does not affect the recovery of the correct MBH value. Our attempt at measuring BH masses in these 3 late type Sbc spiral galaxies has shown that these measurements are very challenging and at the limit of the highest spatial resolution currently available. Nonetheless our estimates are in good agreement with the scaling relations between black holes and their host spheroids suggesting that (i) they are reliable and (ii) black holes in spiral galaxies follow the same scaling relations as those in more massive early-type galaxies. A crucial test for the gas kinematical method, the correct recovery of the known BH mass in NGC 4258, has been successful.

Nuclear clusters, bulges and massive black holes in spiral galaxies

We report on some of the recent work that has come from our Hubble Space Telescope programme to find massive black holes in nearby spiral galaxies. Determining black hole masses from gas kinematics in spiral galaxies is difficult, but results have been reported for NGC 4041 and new results are soon to be reported for NGC 1300 and NGC 2748. Complementary programmes are also looking for the presence of nuclear star clusters in our Space Telescope Imaging Spectrograph (STIS) and archival Near-infrared Camera and Multi-Object Spectrometer (NICMOS) images. We are also currently analysing United Kingdom Infrared Telescope (UKIRT) Fast Track Imager (UFTI) near-infrared images to determine the surface brightness profiles for 37 of the galaxies in the sample. 1. Massive Black Holes in Nearby Spirals Massive black holes seem to be a common component of galactic nuclei. Attempts by the community to establish a demography for massive black holes has lead to various correlations between the mass of the black hole and other host galaxy properties (e.g. Ferrarese & Merritt 2000, Gebhardt et al. 2000, Marconi & Hunt 2003). However, for all these correlations spiral galaxies are relatively under-represented with respect to elliptical galaxies. To address this problem, and in an attempt to quantify the demography of massive black holes in nearby spiral galaxies, we had an HST/STIS programme (GO:8228, PI:Axon) to determine black hole masses using gas dynamics of the nuclear discs in 54 spirals. Marconi et al. (2003) reported the first black hole mass determination from this programme for NGC 4041, while an atlas of the spectra with reasonable signal to noise are presented in Hughes et al. (2003). Examples of some of the spectra and images, plus colour maps made using archival NICMOS images are shown in figure 1. The next paper to report black hole masses from the programme is now near completion (Atkinson et al., in prep) and will present results for NGC 1300 and NGC 2748. 2. Complimentary Work While the main emphasis of the program was to find black hole masses, other complimentary work is underway to understand the environments of the centres of these galaxies. One of the principle host-galaxy properties that has been shown to be correlated with black hole mass is stellar velocity dispersion (Ferrarese & Merritt 2000, Gebhardt 181 182 M. Hughes et al.

Supermassive black holes in spiral galaxies

We have embarked in an HST program to determine the masses of black holes in spiral galaxies directly by measuring the line emission arising from an extended accretion disk. For each of the galaxies in our sample we have measured the rotation curve and determined the mass distribution within the inner 5–50 pc. We have modeled the stellar mass component using the photometric data from existing HST images and using both data sets we have derived the masses of the black holes in each galaxy. These results will be very important in clarifying the role of the black hole in powering the AGN, will shed light into the effectiveness of the accretion mechanisms and finally will be important in addressing the fundamental issue of unification for Seyfert 1 and Seyfert 2 galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Supermassive black holes in spiral galaxies: HST/STIS observations for three new objects

We present long-slit HST/STIS measurements of the ionized-gas kinematics in the nucleus of three disk galaxies, namely NGC 2179, NGC 4343, NGC 4435. The sample galaxies have been selected on the basis of their ground-based spectroscopy, for displaying a strong central velocity gradient for the ionized gas, which is consistent with the presence of a circum nuclear keplerian disk (CNKD, Bertola et al. 1998; Funes et al. 2002) rotating around a super massive black hole (SMBH). For each target galaxy we obtained the Hα and [NII] 6583 A kinematics along the major axis and two 0.25 parallel offset positions. Out of three objects only NGC 4435 turned out to have a disk of ionized gas in regular motion and a regular dust-lane morphology. Preliminary modeling indicates a SMBH mass ( M [bull ] ) one order of magnitude lower than the one expected from the M [bull ] −σ c relation for galaxies (Ferrarese & Merritt 2000; Gebhardt et al. 2000). To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html