scholarly journals Star-Formation and Nuclear Activity in Three Galaxies with Nuclear Rings

1994 ◽  
Vol 159 ◽  
pp. 460-460
Author(s):  
Thaisa Storchi–Bergmann ◽  
Andrew S. Wilson ◽  
Jack A. Baldwin
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Galactic Nuclei ◽  
High Spectral Resolution ◽  
Nuclear Region ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Nuclear Activity ◽  
Line Region ◽  
Low Dispersion

We investigate two current problems in active galactic nuclei – the mode of fueling the putative black hole, and the question whether the circumnuclear regions have experienced unusual chemical processing – by studying the kinematics and chemical abundance of the gas in the nuclear region of galaxies with sites of ongoing star formation near the active nucleus. We discuss the results for three galaxies with nuclear rings: NGC1097 – for which we recently discovered broad double peaked Hα and Hβ emission from its LINER nucleus (Storchi-Bergmann, Baldwin & Wilson 1993, ApJ 410, L11); NGC1672, which also presents a LINER nucleus; and NGC5248, a galaxy with a ring but no nuclear activity, used as a comparison. Narrow–band images obtained with the CTIO 1.5m telescope were used to map the emitting gas. Longslit spectroscopy obtained with the 4m telescope at high spectral resolution (at several positions over the nuclear region) was used to obtain the gas velocity field. In the two galaxies with LINER nucleus, the starforming rings are located in the turnover of the rotation curves, which show that the gas is rotating faster at the rings than farther out. We conclude that the rings are associated with inner Lindblad ressonances, which may be particularly effective in forcing gas inwards and fuelling the black hole (Wilson et al. 1986, ApJ 310, 121). From the emission line ratios the gas excitation is maped, and it is found that even in NGC5248, the nucleus presents a different excitation, suggesting a very mild LINER activity. Low-dispersion spectroscopy was also obtained in order to calculate the chemical abundances and compare the values obtained for the nuclear gas with those obtained for the HII regions in the ring and beyond the ring (when present). The goal is to check the results of recent studies (Storchi-Bergmann & Pastoriza 1989, ApJ 347, 195; 1990, PASP 102, 1359), based on spectroscopy of the nucleus, which indicate an enhanced abundance of nitrogen, up to 5 times solar for the gas of the narrow line region of LINER and Seyfert 2 nuclei.

scholarly journals Velocity Diagnostics of the Broad Emission-Line Region of Active Galactic Nuclei

1997 ◽  
Vol 159 ◽  
pp. 175-178 ◽  
Author(s):  
Brian Espey
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Nuclear Region ◽  
Driving Mechanisms ◽  
Broad Emission ◽  
Line Region ◽  
Broad Emission Line ◽  
Ongoing Project

AbstractWe present a brief review of emission-line velocity differences, and describe an ongoing project to determine the driving mechanisms responsible. We conclude with a brief outline of the use of velocity differences as probes of the conditions in the nuclear region of AGNs.

scholarly journals A CENSUS OF BROAD-LINE ACTIVE GALACTIC NUCLEI IN NEARBY GALAXIES: COEVAL STAR FORMATION AND RAPID BLACK HOLE GROWTH

2013 ◽  
Vol 763 (2) ◽  
pp. 133 ◽  
Author(s):  
Jonathan R. Trump ◽  
Alexander D. Hsu ◽  
Jerome J. Fang ◽  
S. M. Faber ◽  
David C. Koo ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Broad Line ◽  
Black Hole Growth ◽  
Nearby Galaxies ◽  
Hole Growth

scholarly journals The starburst – active galactic nuclei connection on nuclear scales in near by Seyfert galaxies

2013 ◽  
Vol 9 (S304) ◽  
pp. 345-346
Author(s):  
Pilar Esquej
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
High Angular Resolution ◽  
Physical Relation ◽  
Black Hole Accretion ◽  
Star Formation Activity ◽  
Hole Accretion

AbstractSeveral works have shown that there is an empirical correlation between the star formation rate and the luminosity of the active galactic nucleus (and thus the black hole accretion rate, ṀBH) of Seyfert galaxies. This suggests a physical relation between the gas forming stars on kpc scales and the gas on sub-pc scales that is feeding the black hole. Simulations predict this relation and also that the correlation should be more prominent on smaller physical scales. We have compiled high angular resolution (0.4–0.8″) mid-infrared spectroscopy obtained with T-ReCS, VISIR, and Michelle of 29 Seyferts. We use the 11.3 μm PAH feature to probe the star formation activity in the inner ~65 pc, and its relation with the ṀBH on these physical scales.

scholarly journals Black hole mass estimation for active galactic nuclei from a new angle

2019 ◽  
Vol 487 (3) ◽  
pp. 3404-3418 ◽  
Author(s):  
Dalya Baron ◽  
Brice Ménard
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Cosmic Time ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Black Hole Mass ◽  
Mass Estimation ◽  
Line Region

Abstract The scaling relations between supermassive black holes and their host galaxy properties are of fundamental importance in the context black hole-host galaxy co-evolution throughout cosmic time. In this work, we use a novel algorithm that identifies smooth trends in complex data sets and apply it to a sample of 2000 type 1 active galactic nuclei (AGNs) spectra. We detect a sequence in emission line shapes and strengths which reveals a correlation between the narrow L([O iii])/L(H β) line ratio and the width of the broad H α. This scaling relation ties the kinematics of the gas clouds in the broad line region to the ionization state of the narrow line region, connecting the properties of gas clouds kiloparsecs away from the black hole to material gravitationally bound to it on sub-parsec scales. This relation can be used to estimate black hole masses from narrow emission lines only. It therefore enables black hole mass estimation for obscured type 2 AGNs and allows us to explore the connection between black holes and host galaxy properties for thousands of objects, well beyond the local Universe. Using this technique, we present the MBH–σ and MBH–M* scaling relations for a sample of about 10 000 type 2 AGNs from Sloan Digital Sky Survey. These relations are remarkably consistent with those observed for type 1 AGNs, suggesting that this new method may perform as reliably as the classical estimate used in non-obscured type 1 AGNs. These findings open a new window for studies of black hole-host galaxy co-evolution throughout cosmic time.

scholarly journals Feeding and feedback in nearby AGN – comparison with the Milky Way center

2013 ◽  
Vol 9 (S303) ◽  
pp. 354-363 ◽  
Author(s):  
T. Storchi-Bergmann
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Galactic Center ◽  
Formation Rate ◽  
Activity Cycle ◽  
Nuclear Region ◽  
Nuclear Activity ◽  
The Galaxy ◽  
Mass Outflow ◽  
Sgr A

AbstractI discuss feeding and feedback processes observed in the inner few hundred parsecs of nearby active galaxies using integral field spectroscopy at spatial resolutions of a few to tens of parsecs. Signatures of feedback include outflows from the nucleus with velocities ranging from 200 to 1000 km s−1, with mass outflow rates between 0.5 and a few M⊙ yr−1. Signatures of feeding include the observation of gas inflows along nuclear spirals and filaments, with velocities ranging from 50 to 100 km s−1 and mass flow rates from 0.1 to ∼1 M⊙ yr−1. These rates are 2–3 orders of magnitude larger than the mass accretion rate to the supermassive black hole (SMBH). These inflows can thus lead, during less than one activity cycle, to the accumulation of enough gas in the inner few hundred parsecs, to trigger the formation of new stars, leading to the growth of the galaxy bulge. Young to intermediate age stars have indeed been found in circumnuclear rings around a number of Active Galactic Nuclei (AGN). In particular, one of these rings, with radius of ≈ 100 pc is observed in the Seyfert 2 galaxy NGC 1068, and is associated to an off-centered molecular ring, very similar to that observed in the Milky Way (MW). On the basis of an evolutionary scenario in which gas falling into the nuclear region triggers star formation followed by the triggering of nuclear activity, we speculate that, in the case of the MW, molecular gas has already accumulated within the inner ≈ 100 pc to trigger the formation of new stars, as supported by the presence of blue stars close to the galactic center. A possible increase in the star-formation rate in the nuclear region will then be followed, probably tens of millions of years later, by the triggering of nuclear activity in Sgr A*.

scholarly journals The Spitzer Interacting Galaxies Study

2006 ◽  
Vol 2 (S235) ◽  
pp. 190-190
Author(s):  
A. Zezas ◽  
Keyword(s):  
Star Formation ◽  
Galactic Nuclei ◽  
Theoretical Models ◽  
Interacting Galaxies ◽  
Triggered Activity ◽  
Galaxy Interactions ◽  
Nuclear Activity ◽  
Multi Wavelength ◽  
Nuclear Regions ◽  
The Relationship

AbstractGalaxy interactions play an important role in the evolution of galaxies and triggering galaxy-wide star-formation or accretion onto nuclear black-holes. However, the strength and details of the relationship between galaxy interactions and triggered activity are still unclear. In order to address these questions we embarked on a Spitzer multi-wavelength study of a sample of nearby interacting galaxy systems. Our goal is to investigate: how interactions trigger star-formation by studying the spatial distribution and level of star-formation, and comparing them with theoretical models for different interaction parameters; how the interactions drive gas in the nuclear regions, and how this gas promotes and/or hides nuclear activity, by studying the distribution of dust and performing deep spectroscopic observations of the galactic nuclei; and how star-formation and AGN activity depend on the interaction stage.

Role of environment on AGN activity

2019 ◽  
Vol 15 (S356) ◽  
pp. 171-171
Author(s):  
Amirnezam Amiri
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galaxy Clusters ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Local Universe ◽  
Nuclear Activity ◽  
Star Forming ◽  
Star Formation Activity

AbstractMotivated by the apparently conflicting results reported in the literature on the effect of environment on nuclear activity, we have carried out a new analysis by comparing the fraction of galaxies hosting active galactic nuclei (AGNs) in the most overdense regions (rich galaxy clusters) and the most underdense ones (voids) in the local universe. Exploiting the classical BPT diagnostics, we have extracted volume limited samples of star forming and AGN galaxies. We find that, at variance with star-forming galaxies, AGN galaxies have similar distributions of specific star formation rates and of galactic ages (as indicated by the Dn4000 parameter) both in clusters and in voids. In both environments galaxies hosting AGNs are generally old, with low star formation activity. The AGN fraction increases faster with stellar mass in clusters than in voids, especially above 1010.2 M⊙. Our results indicate that, in the local universe, the nuclear activity correlates with stellar mass and galaxy morphology and is weakly, if at all, affected by the local galaxy density.

Estimating the Number of Broad-Line Region Clouds

1999 ◽  
Vol 194 ◽  
pp. 317-318
Author(s):  
M. Dietrich
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Filling Factor ◽  
Galactic Nuclei ◽  
Broad Line ◽  
Central Black Hole ◽  
Continuum Source ◽  
Broad Line Region ◽  
Line Region ◽  
Emission Line Spectrum

The observed emission-line spectrum of active galactic nuclei is consistent with cold dense gas photoionized by a central continuum source (cf. Ferland & Persson 1989). The estimate of the filling factor of the line-emitting region yields f˜10−6 only (cf. Osterbrock 1993) and motivated the picture of numerous clouds moving around a central black hole. Early estimates of the number of BLR clouds indicated a lower limit of 104 to 105 individual clouds (Capriotti et al. 1981; Atwood et al. 1982). Recently, Arav et al. (1998) estimated the number to be at least of the order of 107 discrete emitters. But the number and the nature of these clouds are still unknown.

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