We derive new empirical calibrations for strong-line diagnostics of gas-phase metallicity in local star-forming galaxies by uniformly applying the T sub( e) method over the full metallicity range ...probed by the Sloan Digital Sky Survey (SDSS). To measure electron temperatures at high metallicity, where the auroral lines needed are not detected in single galaxies, we stacked spectra of more than 110 000 galaxies from the SDSS in bins of logOii/H... and logOiii/H... This stacking scheme does not assume any dependence of metallicity on mass or star formation rate, but only that galaxies with the same line ratios have the same oxygen abundance. We provide calibrations which span more than 1 dex in metallicity and are entirely defined on a consistent absolute T sub( e) metallicity scale for galaxies. We apply our calibrations to the SDSS sample and find that they provide consistent metallicity estimates to within 0.05 dex. (ProQuest: ... denotes formulae/symbols omitted.)
We investigate the properties of star-formation-driven outflows by using a large spectroscopic sample of ~160 000 local “normal” star-forming galaxies drawn from the Sloan digital sky survey (SDSS), ...spanning a wide range of star formation rates (SFRs) and stellar masses (M∗). The galaxy sample is divided into a fine grid of bins in the M∗−SFR parameter space, for each of which we produced a composite spectrum by stacking the SDSS spectra of the galaxies contained in that bin together. We exploited the high signal-to-noise of the stacked spectra to study the emergence of faint features of optical emission lines that may trace galactic outflows and are otherwise too faint to detect in individual galaxy spectra. We have adopted a novel approach that relies on the comparison between the line-of-sight velocity distribution (LoSVD) of the ionised gas (as traced by the OIIIλ5007 and Hα+NIIλλ6548, 6583 emission lines) and the LoSVD of the stars, which are used as a reference for tracing virial motions. Significant deviations in the gas kinematics from the stellar kinematics in the high-velocity tail of the LoSVDs are interpreted as a signature of outflows. Our results suggest that the incidence of ionised outflows increases with SFR and specific SFR. The outflow velocity (vout) is found to correlate tightly with the SFR for SFR> 1 M⊙ yr-1, whereas the dependence of vout on SFR is nearly flat at lower SFRs. The outflow velocity appears to also increase with the stellar velocity dispersion (σ∗), although this relation has a much larger scatter than the one with SFR, and we infer velocities as high as vout ~ (6−8)σ∗. Strikingly, we detect the signature of ionised outflows only in galaxies located above the main sequence (MS) of star-forming galaxies in the M∗−SFR diagram, and the incidence of such outflows increases sharply with the offset from the MS. This result suggests that star-formation-driven outflows may be responsible for shaping the upper envelope of the MS by providing a self-regulating mechanism for star formation. Finally, our complementary analysis of the stellar kinematics reveals the presence of blue asymmetries of a few 10 km s-1 in the stellar LoSVDs. The origin of such asymmetries is not clear, but a possibility is that they trace the presence of a large number of high velocity runaway stars and hypervelocity stars in radial trajectories in local galaxies.
We show that the mass–metallicity relation observed in the local universe is due to a more general relation between stellar mass M★, gas-phase metallicity and star formation rate (SFR). Local ...galaxies define a tight surface in this 3D space, the fundamental metallicity relation (FMR), with a small residual dispersion of ∼0.05 dex in metallicity, i.e. ∼12 per cent. At low stellar mass, metallicity decreases sharply with increasing SFR, while at high stellar mass, metallicity does not depend on SFR. High-redshift galaxies up to z∼ 2.5 are found to follow the same FMR defined by local Sloan Digital Sky Survey (SDSS) galaxies, with no indication of evolution. In this respect, the FMR defines the properties of metal enrichment of galaxies in the last 80 per cent of cosmic time. The evolution of the mass–metallicity relation observed up to z= 2.5 is due to the fact that galaxies with progressively higher SFRs, and therefore lower metallicities, are selected at increasing redshifts, sampling different parts of the same FMR. By introducing the new quantity μα= log (M★) −α log (SFR), with α= 0.32, we define a projection of the FMR that minimizes the metallicity scatter of local galaxies. The same quantity also cancels out any redshift evolution up to z∼ 2.5, i.e. all galaxies follow the same relation between μ0.32 and metallicity and have the same range of values of μ0.32. At z > 2.5, evolution of about 0.6 dex off the FMR is observed, with high-redshift galaxies showing lower metallicities. The existence of the FMR can be explained by the interplay of infall of pristine gas and outflow of enriched material. The former effect is responsible for the dependence of metallicity with SFR and is the dominant effect at high redshift, while the latter introduces the dependence on stellar mass and dominates at low redshift. The combination of these two effects, together with the Schmidt–Kennicutt law, explains the shape of the FMR and the role of μ0.32. The small-metallicity scatter around the FMR supports the smooth infall scenario of gas accretion in the local universe.
Context. Feedback from accreting supermassive black holes (SMBHs) is often identified as the main mechanism responsible for regulating star formation in active galactic nucleus (AGN) host galaxies. ...However, the relationships between AGN activity, radiation, winds, and star formation are complex and still far from being understood. Aims. We study scaling relations between AGN properties, host galaxy properties, and AGN winds. We then evaluate the wind mean impact on the global star formation history, taking into account the short AGN duty cycle with respect to that of star formation. Methods. We first collect AGN wind observations for 94 AGN with detected massive winds at sub-pc to kpc spatial scales. We then fold AGN wind scaling relations with AGN luminosity functions, to evaluate the average AGN wind mass-loading factor as a function of cosmic time. Results. We find strong correlations between the AGN molecular and ionised wind mass outflow rates and the AGN bolometric luminosity. The power law scaling is steeper for ionised winds (slope 1.29 ± 0.38) than for molecular winds (0.76 ± 0.06), meaning that the two rates converge at high bolometric luminosities. The molecular gas depletion timescale and the molecular gas fraction of galaxies hosting powerful AGN driven winds are 3–10 times shorter and smaller than those of main sequence galaxies with similar star formation rate (SFR), stellar mass, and redshift. These findings suggest that, at high AGN bolometric luminosity, the reduced molecular gas fraction may be due to the destruction of molecules by the wind, leading to a larger fraction of gas in the atomic ionised phase. The AGN wind mass-loading factor η = ṀOF/SFR is systematically higher than that of starburst driven winds. Conclusions. Our analysis shows that AGN winds are, on average, powerful enough to clean galaxies from their molecular gas only in massive systems at z ≲ 2, i.e. a strong form of co-evolution between SMBHs and galaxies appears to break down for the least massive galaxies.
Context.
The AGN bolometric correction is a key element for understanding black hole (BH) demographics and computing accurate BH accretion histories from AGN luminosities. However, current estimates ...still differ from each other by up to a factor of two to three, and rely on extrapolations at the lowest and highest luminosities.
Aims.
Here we revisit this fundamental question by presenting general hard X-ray (
K
X
) and optical (
K
O
) bolometric corrections, computed by combining several AGN samples spanning the widest (about 7 dex) luminosity range ever used for this type of studies.
Methods.
We analysed a total of ∼1000 type 1 and type 2 AGN for which we performed a dedicated SED-fitting.
Results.
We provide a bolometric correction separately for type 1 and type 2 AGN; the two bolometric corrections agree in the overlapping luminosity range. Based on this we computed for the first time a universal bolometric correction for the whole AGN sample (both type 1 and type 2). We found that
K
X
is fairly constant at log(
L
BOL
/
L
⊙
) < 11, while it increases up to about one order of magnitude at log(
L
BOL
/
L
⊙
) ∼ 14.5. A similar increasing trend has been observed when its dependence on either the Eddington ratio or the BH mass is considered, while no dependence on redshift up to
z
∼ 3.5 has been found. In contrast, the optical bolometric correction appears to be fairly constant (i.e.
K
O
∼ 5) regardless of the independent variable. We also verified that our bolometric corrections correctly predict the AGN bolometric luminosity functions. According to this analysis, our bolometric corrections can be applied to the whole AGN population in a wide range of luminosity and redshift.
Mrk 231 is a nearby ultra-luminous IR galaxy exhibiting a kpc-scale, multi-phase AGN-driven outflow. This galaxy represents the best target to investigate in detail the morphology and energetics of ...powerful outflows, as well as their still poorly-understood expansion mechanism and impact on the host galaxy. In this work, we present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk 231, as traced by CO(2−1) and (3−2) observations obtained with the IRAM/PdBI. In addition, we analyze archival deep Chandra and NuSTAR X-ray observations. We use this unprecedented combination of multi-wavelength data sets to constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The molecular CO(2−1) outflow has a size of ~1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. The maximum projected velocity of the outflow is nearly constant out to ~1 kpc, thus implying that the density of the outflowing material must decrease from the nucleus outwards as ~r-2. This suggests that either a large part of the gas leaves the flow during its expansion or that the bulk of the outflow has not yet reached out to ~1 kpc, thus implying a limit on its age of ~1 Myr. Mapping the mass and energy rates of the molecular outflow yields \hbox{$\rm \dot {\it M}$}M˙ OF = 500−1000 M⊙ yr-1 and Ėkin,OF = 7−10 × 1043 erg s-1. The total kinetic energy of the outflow is Ekin,OF is of the same order of the total energy of the molecular disk, Edisk. Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow (UFO) with velocity −20 000 km s-1, \hbox{$\rm \dot {\it M}$} M ˙ UFO = 0.3−2.1 M⊙ yr-1, and momentum load \hbox{$\rm \dot {\it P}$} P ˙ UFO/ \hbox{$\dot {\it P}$} P ˙ rad = 0.2−1.6. We find Ėkin,UFO ~ Ėkin,OF as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows. The momentum flux \hbox{$\rm \dot {\it P}$} P ˙ OF derived for the large scale outflows in Mrk 231 enables us to estimate a momentum boost \hbox{$\rm \dot {\it P}$} P ˙ OF/ \hbox{$\dot {\it P}$} P ˙ UFO ≈ 30−60. The ratios Ėkin,UFO/Lbol,AGN = 1−5 % and Ėkin,OF/Lbol,AGN = 1−3 % agree with the requirements of the most popular models of AGN feedback.
We present a mid-infrared investigation of the scaling relations between supermassive black hole masses (M
BH) and the structural parameters of the host spheroids in local galaxies. This work is ...based on 2D bulge-disc decompositions of Spitzer/IRAC 3.6 μm images of 57 galaxies with M
BH estimates. We first verify the accuracy of our decomposition by examining the Fundamental Plane (FP) of spheroids at 3.6 μm. Our estimates of effective radii (R
e) and average surface brightnesses, combined with velocity dispersions from the literature, define a FP relation consistent with previous determinations but doubling the observed range in R
e. None of our galaxies is an outlier of the FP, demonstrating the accuracy of our bulge-disc decomposition which also allows us to independently identify pseudo-bulges in our sample. We calibrate M/L at 3.6 μm by using the tight M
dyn-L
bul relation (∼0.1 dex intrinsic dispersion) and find that no colour corrections are required to estimate the stellar mass. The 3.6 μm luminosity is thus the best tracer of stellar mass yet studied. We then explore the connection between M
BH and bulge structural parameters (luminosity, mass, effective radius). We find tight correlations of M
BH with both 3.6 μm bulge luminosity and dynamical mass (M
BH/M
dyn∼ 1/1000), with intrinsic dispersions of ∼0.35 dex, similar to the M
BH-σ relation. Our results are consistent with previous determinations at shorter wavelengths. By using our calibrated M/L, we rescale M
BH-L
bul to obtain the M
BH-M
★ relation, which can be used as the local reference for high-z studies which probe the cosmic evolution of M
BH-galaxy relations and where the stellar mass is inferred directly from luminosity measurements. The analysis of pseudo-bulges shows that four out of nine lie on the scaling relations within the observed scatter, while those with small M
BH are significantly displaced. We explore the different origins for such behaviour while considering the possibility of nuclear morphological components not reproduced by our 2D decomposition.
Context.
The existence of tight correlations between supermassive black holes (BHs) and their host galaxies’ properties in the local Universe suggests a closely linked evolution. Investigating these ...relations up to the high redshifts (
z
≳ 6) is crucial in order to understand the interplay between star formation and BH growth across the cosmic time and to set constraints on galaxy formation and evolution models. In this work, we focus on the relation between BH mass (
M
BH
) and the dynamical mass (
M
dyn
) of the host galaxy.
Aims.
Previous works suggest an evolution of the
M
BH
−
M
dyn
relation with redshift indicating that BH growth precedes the galaxy mass assembly during their co-evolution at
z
> 3. However, dynamical galaxy masses at high redshift are often estimated through the virial theorem, thus introducing significant uncertainties. Within the scope of this work, our aim is to study the
M
BH
−
M
dyn
relation of a sample of 2 <
z
< 7 quasars by constraining their galaxy masses through a full kinematical modelling of the cold gas kinematics, thus avoiding all possible biases and effects introduced by the rough estimates usually adopted so far.
Methods.
For this purpose, we retrieved public observations of 72 quasar host galaxies observed in CII
158 μm
or CO transitions with the Atacama Large Millimeter Array (ALMA). We then selected those quasars whose line emission is spatially resolved, and performed a kinematic analysis on ALMA observations. We estimated the dynamical mass of the systems by modelling the gas kinematics with a rotating disc, taking into account geometrical and instrumental effects. Our dynamical mass estimates, combined with
M
BH
obtained from literature and our own new CIV
λ
1550 observations allowed us to investigate the
M
BH
/
M
dyn
in the early Universe.
Results.
Overall, we obtained a sample of ten quasars at
z
∼ 2−7, in which line emission is detected with high S/N (≳5−10) and the gas kinematics are spatially resolved and dominated by ordered rotation. The estimated dynamical masses place six out of ten quasars above the local relation yielding to
M
BH
/
M
dyn
ratios ∼10× higher than those estimated in low-
z
galaxies. On the other hand, we found that four quasars at
z
∼ 4−6 have dynamical-to-BH-mass ratios consistent with what is observed in early-type galaxies in the local Universe.
Negative feedback from active galactic nuclei (AGN) is considered a key mechanism in shaping galaxy evolution. Fast, extended outflows are frequently detected in the AGN host galaxies at all ...redshifts and luminosities, both in ionised and molecular gas. However, these outflows are only potentially able to quench star formation, and we are still lacking decisive evidence of negative feedback in action. Here we present observations obtained with the Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) H- and K-band integral-field of two quasars at z ~ 2.4 that are characterised by fast, extended outflows detected through the Oiiiλ5007 line. The high signal-to-noise ratio of our observations allows us to identify faint narrow (FWHM< 500 km s-1) and spatially extended components in Oiiiλ5007 and Hα emission associated with star formation in the host galaxy. This star formation powered emission is spatially anti-correlated with the fast outflows. The ionised outflows therefore appear to be able to suppress star formation in the region where the outflow is expanding. However, the detection of narrow spatially extended Hα emission indicates star formation rates of at least ~50–90 M⊙ yr-1, suggesting either that AGN feedback does not affect the whole galaxy or that many feedback episodes are required before star formation is completely quenched. On the other hand, the narrow Hα emission extending along the edges of the outflow cone may also lead also to a positive feedback interpretation. Our results highlight the possible double role of galaxy-wide outflows in host galaxy evolution.
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