Quasars are rapidly accreting supermassive black holes at the centres of massive galaxies. They display a broad range of properties across all wavelengths, reflecting the diversity in the physical ...conditions of the regions close to the central engine. These properties, however, are not random, but form well-defined trends. The dominant trend is known as 'Eigenvector 1', in which many properties correlate with the strength of optical iron and O III emission. The main physical driver of Eigenvector 1 has long been suspected to be the quasar luminosity normalized by the mass of the hole (the 'Eddington ratio'), which is an important parameter of the black hole accretion process. But a definitive proof has been missing. Here we report an analysis of archival data that reveals that the Eddington ratio indeed drives Eigenvector 1. We also find that orientation plays a significant role in determining the observed kinematics of the gas in the broad-line region, implying a flattened, disk-like geometry for the fast-moving clouds close to the black hole. Our results show that most of the diversity of quasar phenomenology can be unified using two simple quantities: Eddington ratio and orientation.
Intermediate-Mass Black Holes Greene, Jenny E; Strader, Jay; Ho, Luis C
Annual review of astronomy and astrophysics,
08/2020, Volume:
58, Issue:
1
Journal Article
Peer reviewed
We describe ongoing searches for intermediate-mass black holes with
M
BH
≈ 10-10
5
M
. We review a range of search mechanisms, both dynamical and those that rely on accretion signatures. We find the ...following conclusions:
Dynamical and accretion signatures alike point to a high fraction of 10
9
-10
10
M
galaxies hosting black holes with
M
BH
∼ 10
5
M
. In contrast, there are no solid detections of black holes in globular clusters.
There are few observational constraints on black holes in any environment with
M
BH
≈ 100-10
4
M
.
Considering low-mass galaxies with dynamical black hole masses and constraining limits, we find that the
M
BH
-σ
*
relation continues unbroken to
M
BH
∼10
5
M
, albeit with large scatter. We believe the scatter is at least partially driven by a broad range in black hole masses, because the occupation fraction appears to be relatively high in these galaxies.
We fold the observed scaling relations with our empirical limits on occupation fraction and the galaxy mass function to put observational bounds on the black hole mass function in galaxy nuclei.
We are pessimistic that local demographic observations of galaxy nuclei alone could constrain seeding mechanisms, although either high-redshift luminosity functions or robust measurements of off-nuclear black holes could begin to discriminate models.
The mass estimator used to calculate black hole (BH) masses in broad-line active galactic nuclei (AGNs) relies on a virial coefficient (the "f factor") that is determined by comparing ...reverberation-mapped (RM) AGNs with measured bulge stellar velocity dispersions against the M sub(BH-)sigma* relation of inactive galaxies. It has recently been recognized that only classical bulges and ellipticals obey a tight M sub(BH-)sigma* relation; pseudobulges have a different zero point and much larger scatter. Motivated by these developments, we reevaluate the f factor for RM AGNs with available sigma sub(*) measurements, updated H beta RM lags, and new bulge classifications based on detailed decomposition of high-resolution ground-based and space-based images. Separate calibrations are provided for the two bulge types, whose virial coefficients differ by a factor of ~2: f = 6.3 + or - 1.5 for classical bulges and ellipticals and f = 3.2 + or - 0.7 for pseudobulges. The structure and kinematics of the broad-line region, at least as crudely encoded in the f factor, seems to be related to the large-scale properties or formation history of the bulge. Lastly, we investigate the bulge stellar masses of the RM AGNs, show evidence for recent star formation in the AGN hosts that correlates with Eddington ratio, and discuss the potential utility of the M sub(BH)-M sub(bulge) relation as a more promising alternative to the conventionally used M sub(BH-)sigma* relation for future refinement of the virial mass estimator for AGNs.
The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. However, direct gas measurements are ...limited by sensitivity and other uncertainties. Dust provides an efficient indirect probe of the total gas. We apply this technique to a large sample of quasars, whose total gas content would be prohibitively expensive to measure. We present a comprehensive study of the full (1 to 500 m) infrared spectral energy distributions of 87 redshift <0.5 quasars selected from the Palomar-Green sample, using photometric measurements from 2MASS, WISE, and Herschel, combined with Spitzer mid-infrared (5-40 m) spectra. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we decompose various overlapping contributions to the integrated spectral energy distribution, including starlight, warm dust from the torus, and cooler dust on galaxy scales. This procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass. Most (90%) quasar hosts have gas fractions similar to those of massive, star-forming galaxies, although a minority (10%) seem genuinely gas-deficient, resembling present-day massive early-type galaxies. This result indicates that "quasar mode" feedback does not occur or is ineffective in the host galaxies of low-redshift quasars. We also find that quasars can boost the interstellar radiation field and heat dust on galactic scales. This cautions against the common practice of using the far-infrared luminosity to estimate the host galaxy star formation rate.
Polycyclic aromatic hydrocarbon (PAH) emission has long been proposed to be a potential star formation rate indicator, as it arises from the photodissociation region bordering the Strömgren sphere of ...young, massive stars. We apply a recently developed technique of mid-infrared spectral decomposition to obtain a uniform set of PAH measurements from Spitzer low-resolution spectra of a large sample of star-forming galaxies spanning a wide range in stellar mass (M 106-1011.4 M ) and star formation rate (∼0.1-2000 M yr−1). High-resolution spectra are also analyzed to measure Ne ii 12.8 m and Ne iii 15.6 m, which effectively trace the Lyman continuum. We present a new relation between PAH luminosity and star formation rate based on the Ne ii and Ne iii lines. Calibrations are given for the integrated 5-15 m PAH emission, the individual features at 6.2, 7.7, 8.6, and 11.3 m, as well as several mid-infrared bandpasses sensitive to PAH. We confirm that PAH emission is suppressed in low-mass dwarf galaxies, and we discuss the possible physical origin of this effect.
Abstract
Feedback from active galactic nuclei (AGNs) is expected to impact the amount of cold gas in galaxies by driving strong galactic winds, by preventing external gas inflows, or by changing the ...thermodynamical state of the gas. We use estimates of molecular gas mass based on dust absorption (H
α
/H
β
) to study gas content of large samples of type 2 AGN host galaxies in comparison with inactive galaxies. Using sparse principal component and clustering analysis, we analyze a suite of stellar and structural parameters of ∼27,100 face-on, central galaxies at redshift
z
= 0.02–0.15 and with stellar mass
M
⋆
≈ 10
10
–2 × 10
11
M
⊙
. We identify four galaxy groups of similar mass and morphology (mass surface density, velocity dispersion, concentration, and Sérsic index) that can be evolutionarily linked through a life cycle wherein gas content mediates their star formation rate (SFR) and level of AGN activity. Galaxies first consume their gas mostly through bursty star formation, then enter into a transition phase of intermediate gas richness in which star formation and AGNs coexist, before settling into retirement as gas-poor, quiescent systems with residual levels of AGN activity (LINERs). Strongly accreting black holes (Seyferts) live in gas-rich, star-forming hosts, but neither their gas reservoir nor their ability to form stars seems to be impacted
instantaneously
(timescales ≲0.5 Gyr) by AGN feedback. Our results are inconsistent with AGN feedback models that predict that central, bulge-dominated, Seyfert-like AGNs in massive galaxies have significantly lower molecular gas fractions than inactive galaxies of similar mass, morphology, and SFR.
Abstract
We combine mid-infrared diagnostics obtained from integral-field-unit observations taken with Mid-Infrared Instrument/Medium Resolution Spectrograph on the James Webb Space Telescope with ...cold molecular gas information derived from Atacama Large Millimeter/submillimeter Array observations of CO(1–0) emission to investigate the star formation rate and efficiency within the central ∼1.5 kpc × 1.3 kpc region of the Seyfert 1 galaxy NGC 7469 on ∼100 pc scales. The active nucleus leaves a notable imprint on its immediate surroundings by elevating the temperature of the warm molecular gas, driving an ionized gas outflow on subkiloparsec scales, and selectively destroying small dust grains. These effects, nevertheless, have relatively little impact on the cold circumnuclear medium or its ability to form stars. Most of the star formation in NGC 7469 is confined to a clumpy starburst ring, but the star formation efficiency remains quite elevated even for the nuclear region that is most affected by the active nucleus.
Type 2 quasars are an important constituent of active galaxies, possibly representing the evolutionary precursors of traditionally studied type 1 quasars. We characterize the black hole (BH) mass ...(MBH) and Eddington ratio (Lbol/LEdd) for 669 type 2 quasars selected from the Sloan Digital Sky Survey, using BH masses estimated from the MBH- * relation and bolometric corrections scaled from the extinction-corrected O iii λ5007 luminosity. When stellar velocity dispersions cannot be measured directly from the spectra, we estimate them from the core velocity dispersions of the narrow emission lines O ii λλ3726, 3729, S ii λλ6716, 6731, and O iii λ5007, which are shown to trace the gravitational potential of the stars. Energy input from the active nucleus still imparts significant perturbations to the gas kinematics, especially to high-velocity, blueshifted wings. Nonvirial motions in the gas become most noticeable in systems with high Eddington ratios. The BH masses of our sample of type 2 quasars range from MBH 106.5 to 1010.4 M (median 108.2 M ). Type 2 quasars have characteristically large Eddington ratios (Lbol/LEdd 10−2.9-101.8; median 10−0.7), slightly higher than in type 1 quasars of similar redshift; the luminosities of ∼20% of the sample formally exceed the Eddington limit. The high Eddington ratios may be consistent with the notion that obscured quasars evolve into unobscured quasars.
In a popular scenario for the coevolution of massive black holes and galaxies, major mergers of gas-rich galaxies fuel vigorous star formation and obscured (type 2) quasar activity until energy ...feedback from the active galactic nucleus (AGN) clears away the gas and dust to reveal an unobscured (type 1) quasar. Under this scenario, the precursor type 2 quasars should be more gas-rich than their type 1 counterparts, and both types of quasars are expected to be gas-deficient relative to normal, star-forming galaxies of similar stellar mass. We test this evolutionary hypothesis by investigating the infrared (∼1-500 m) spectral energy distribution of 86 optically selected z < 0.5 type 2 quasars, matched in redshift and O iii luminosity to a comparison sample of type 1 quasars. Contrary to expectations, the gas content of the host galaxies of type 2 quasars is nearly indistinguishable from that of type 1 quasar hosts, and neither type exhibits the predicted deficit in gas relative to normal galaxies. The gas mass fraction of quasar hosts appears unaffected by the bolometric luminosity of the active nucleus, although their interstellar radiation field is preferentially higher than that of normal galaxies, potentially implicating AGN heating of the large-scale galactic dust.
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