The near-to-mid infrared spectrum of quasars Hernán-Caballero, Antonio; Hatziminaoglou, Evanthia; Alonso-Herrero, Almudena ...
Monthly notices of the Royal Astronomical Society,
12/2016, Volume:
463, Issue:
2
Journal Article
Peer reviewed
Open access
We analyse a sample of 85 luminous (log...(...L sub( ...)(3 ...m)/erg s super( -1)) > 45.5) quasars with rest frame ~2-11 ...m spectroscopy from AKARI and Spitzer. Their high luminosity allows a ...direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disc and two blackbodies for the dust emission successfully reproduces the 0.1-10 ...m spectral energy distributions (SEDs). Excess emission at 1-2 ...m over the best-fitting model suggests that hotter dust is necessary in addition to the ~1200 K blackbody and the disc to reproduce the entire near-infrared spectrum. Variation in the extinction affecting the disc and in the relative strength of the disc and dust components accounts for the diversity of individual SEDs. Quasars with higher dust-to-disc luminosity ratios show slightly redder infrared continua and less prominent silicate emission. We find no luminosity dependence in the shape of the average infrared quasar spectrum. We generate a new quasar template that covers the rest-frame range 0.1-11 ...m, and separate templates for the disc and dust components. Comparison with other infrared quasar composites suggests that previous ones are less reliable in the 2-4 ...m range. Our template is the first one to provide a detailed view of the infrared emission on both sides of the 4 ...m bump. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
Observations have found black holes spanning 10 orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is, however, provisional as its behavior at infinity ...is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole’s interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over 0 <
z
≲ 2.5. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at
z
≲ 7, black holes contribute an effectively constant cosmological energy density to Friedmann’s equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of Ω
Λ
measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at
z
∼ 0.7.
Abstract
The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since
z
∼ 1 can help to diagnose the origins of locally observed correlations between SMBH mass and ...stellar mass. We therefore construct three samples of elliptical galaxies, one at
z
∼ 0 and two at 0.7 ≲
z
≲ 2.5, and quantify their relative positions in the
M
BH
−
M
*
plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher-redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of 7 between
z
∼ 1 and
z
∼ 0. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of ∼20 at
z
∼ 2. The result is robust against variation in the high- and low-redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at
z
≲ 2, or that selection and measurement biases are both underestimated, and depend on redshift.
We investigate the relation between star formation rates (
$\dot{{M}}_s$
) and AGN properties in optically selected type 1 quasars at 2 < z < 3 using data from Herschel and the SDSS. We find that
...$\dot{{M}}_s$
remains approximately constant with redshift, at 300 ± 100 M⊙ yr−1. Conversely,
$\dot{{M}}_s$
increases with AGN luminosity, up to a maximum of ∼ 600 M⊙ yr−1, and with C iv FWHM. In context with previous results, this is consistent with a relation between
$\dot{{M}}_s$
and black hole accretion rate (
$\dot{{M}}_{{\rm bh}}$
) existing in only parts of the
$z-\dot{{M}}_{s}-\dot{{M}}_{{\rm bh}}$
plane, dependent on the free gas fraction, the trigger for activity, and the processes that may quench star formation. The relations between
$\dot{{M}}_s$
and both AGN luminosity and C iv FWHM are consistent with star formation rates in quasars scaling with black hole mass, though we cannot rule out a separate relation with black hole accretion rate. Star formation rates are observed to decline with increasing C iv equivalent width. This decline can be partially explained via the Baldwin effect, but may have an additional contribution from one or more of three factors; M
i
is not a linear tracer of L
2500, the Baldwin effect changes form at high AGN luminosities, and high C iv EW values signpost a change in the relation between
$\dot{{M}}_s$
and
$\dot{{M}}_{{\rm bh}}$
. Finally, there is no strong relation between
$\dot{{M}}_s$
and Eddington ratio, or the asymmetry of the C iv line. The former suggests that star formation rates do not scale with how efficiently the black hole is accreting, while the latter is consistent with C iv asymmetries arising from orientation effects.
We examine the origin of molecular gas heating in a sample of 42 infrared-luminous galaxies at z<0.3 by combining two sets of archival data: first, integrated CO line luminosities in the 1–0 and 5–4 ...through 13–12 transitions; second, results from radiative transfer modelling that decompose their bolometric emission into starburst, AGN, and host galaxy components. We find that the CO 1–0 and 5–4 through 9–8 lines primarily arise via radiative heating in the starburst and the host galaxy. In contrast, the CO 10–9 through 13–12 lines may arise primarily in the starburst and AGN, with an increasing contribution from mechanical heating and shocks. For the sample as a whole, we find no evidence that AGN luminosity affects the heating of molecular gas by star formation. However, for starbursts with low initial optical depths, a more luminous AGN may reduce the efficiency of starburst heating of the CO 5–4 and above lines, consistent with negative AGN feedback.
We use a semi-empirical model to reproduce the 0.1–10 μm spectral energy distribution (SED) of a sample of 85 luminous quasars. In the model, the continuum emission from the accretion disk as well as ...the nebular lines are represented by a single empirical template (disk), where differences in the optical spectral index are reproduced by varying the amount of extinction. The near- and mid-infrared emission of the AGN-heated dust is modeled as the combination of two black-bodies (dust). The model fitting shows that the disk and dust components are remarkably uniform among individual quasars, with differences in the observed SED largely accounted for by varying levels of obscuration in the disk as well as differences in the relative luminosity of the disk and dust components. By combining the disk-subtracted SEDs of the 85 quasars, we generate a template for the 1–10 μm emission of the AGN-heated dust. Additionally, we use a sample of local Seyfert 1 galaxies with full spectroscopic coverage in the 0.37–39 μm range to demonstrate a method for stitching together spectral segments obtained with different PSF and extraction apertures. We show that the disk and dust templates obtained from luminous quasars also reproduce the optical-to-mid-infrared spectra of local Seyfert 1s when the contribution from the host galaxy is properly subtracted.
We have used far-infrared data from IRAS, Infrared Space Observatory (ISO), Spitzer Wide-Area Infrared Extragalactic (SWIRE), Submillimetre Common User Bolometer Array (SCUBA) and Max-Planck ...Millimetre Bolometer (MAMBO) to constrain statistically the mean far-infrared luminosities of quasars. Our quasar compilation at redshifts 0 < z < 6.5 and I-band luminosities −20 < IAB < −32 is the first to distinguish evolution from quasar luminosity dependence in such a study. We carefully cross-calibrate IRAS against Spitzer and ISO, finding evidence that IRAS 100-μm fluxes at <1 Jy are overestimated by ∼30 per cent. We find evidence for a correlation between star formation in quasar hosts and the quasar optical luminosities, varying as star formation rate (SFR) ∝L0.44±0.07opt at any fixed redshift below z= 2. We also find evidence for evolution of the mean SFR in quasar host galaxies, scaling as (1 +z)1.6±0.3 at z < 2 for any fixed quasar I-band absolute magnitude fainter than −28. We find no evidence for any correlation between SFR and black hole mass at 0.5 < z < 4. Our data are consistent with feedback from black hole accretion regulating stellar mass assembly at all redshifts.
ABSTRACT
We study stellar and black hole mass assembly in a sample of 42 infrared-luminous galaxy mergers at z < 0.3 by combining results from radiative transfer modelling with archival measures of ...molecular gas and black hole mass. The ratios of stellar mass, molecular gas mass, and black hole mass to each other are consistent with those of massive gas-rich galaxies at z < 0.3. The advanced mergers may show increased black hole mass to stellar mass ratios, consistent with the transition from active galactic nucleus (AGN) to ellipticals and implying substantial black hole mass growth over the course of the merger. Star formation rates are enhanced relative to the local main sequence, by factors of ∼100 in the starburst and ∼1.8 in the host, respectively. The starburst star formation rates appear distinct to star formation in the main sequence at all redshifts up to at least z ∼ 5. Starbursts may prefer late-stage mergers, but are observed at any merger stage. We do not find evidence that the starbursts in these low-redshift systems substantially increase the total stellar mass, with a soft upper limit on the stellar mass increase from starburst activity of about a factor of two. In contrast, 12 objects show evidence for super-Eddington accretion, associated with late-stage mergers, suggesting that many AGN in infrared-luminous mergers go through a super-Eddington phase. The super-Eddington phase may increase black hole mass by up to an order of magnitude at an accretion efficiency of $42\pm 33{{\ \rm per\ cent}}$ over a period of 44 ± 22 Myr. Our results imply that super-Eddington accretion is an important black hole growth channel in infrared-luminous galaxies at all redshifts.
ABSTRACT
We present a detailed study of a high-redshift iron low-ionization broad absorption line (FeLoBAL) quasar (SDSS1214 at $z$ = 1.046), including new interferometric 12CO J = 2–1 observations, ...optical through far-infrared photometry, and mid-infrared spectroscopy. The CO line is well fit by a single Gaussian centred 40 km s−1 away from the systemic velocity and implies a total molecular gas mass of $M_{\rm gas} = 7.3 \times 10^{10}\, {\rm M}_\odot$. The infrared spectral energy distribution requires three components: an active galactic nucleus (AGN) torus, an AGN polar dust component, and a starburst. The starburst dominates the infrared emission with a luminosity of log$(L_{\rm SB}{\rm L}_\odot ) = 12.91^{+0.02}_{-0.02}$, implying a star formation rate of about 2000 M⊙yr−1, the highest known among FeLoBAL quasars. The AGN torus and polar dust components are less luminous, at log$(L_{\rm AGN}{\rm L}_\odot ) = 12.36^{+0.14}_{-0.15}$ and log$(L_{\rm dust}{\rm L}_\odot ) = 11.75^{+0.26}_{-0.46}$, respectively. If all of the molecular gas is used to fuel the ongoing star formation, then the lower limit on the subsequent duration of the starburst is 40 Myr. We do not find conclusive evidence that the AGN is affecting the CO gas reservoir. The properties of SDSS1214 are consistent with it representing the endpoint of an obscured starburst transitioning through a LoBAL phase to that of a classical quasar.
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