Extremely compact massive galaxies at z ∼ 1.4 Trujillo, I.; Feulner, G.; Goranova, Y. ...
Monthly notices of the Royal Astronomical Society,
November 2006, Letnik:
373, Številka:
1
Journal Article
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The optical rest-frame sizes of 10 of the most massive (∼5 × 1011 h−270 M⊙) galaxies found in the near-infrared MUNICS survey at 1.2 < z < 1.7 are analysed. Sizes are estimated in both the J and K′ ...filters. These massive galaxies are at least a factor of 4+1.9−1.0 (±1σ) smaller in the rest-frame V-band than local counterparts of the same stellar mass. Consequently, the stellar mass density of these objects is (at least) 60 times larger than that of massive ellipticals today. Although the stellar populations of these objects are passively fading, their structural properties are rapidly changing since that redshift. This observational fact disagrees with a scenario where the more massive and passive galaxies are fully assembled at z∼ 1.4 (i.e. a monolithic scenario) and points towards a dry merger scenario as the responsible mechanism for the subsequent evolution of these galaxies.
SUPER Vietri, G.; Mainieri, V.; Kakkad, D. ...
Astronomy and astrophysics (Berlin),
12/2020, Letnik:
644
Journal Article
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Aims.
The SINFONI survey for Unveiling the Physics and Effect of Radiative feedback (SUPER) was designed to conduct a blind search for AGN-driven outflows on X-ray-selected AGNs at redshift
z
∼ 2 ...with high (∼2 kpc) spatial resolution, and to correlate them with the properties of their host galaxy and central black hole. The main aims of this paper are: (a) to derive reliable estimates for the masses of the black holes and accretion rates for the Type-1 AGNs in this survey; and (b) to characterise the properties of the AGN-driven winds in the broad line region (BLR).
Methods.
We analysed rest-frame optical and UV spectra of 21 Type-1 AGNs. We used H
α
, H
β
, and MgII line profiles to estimate the masses of the black holes. We used the blueshift of the CIV line profile to trace the presence of winds in the BLR.
Results.
We find that the H
α
and H
β
line widths are strongly correlated, as is the line continuum luminosity at 5100 Å with H
α
line luminosity, resulting in a well-defined correlation between black hole masses estimated from H
α
and H
β
. Using these lines, we estimate that the black hole masses for our objects are in the range Log (
M
BH
/
M
⊙
) = 8.4–10.8 and are accreting at
λ
Edd
= 0.04–1.3. Furthermore, we confirm the well-known finding that the CIV line width does not correlate with the Balmer lines and the peak of the line profile is blueshifted with respect to the OIII-based systemic redshift. These findings support the idea that the CIV line is tracing outflowing gas in the BLR for which we estimated velocities up to ∼4700 km s
−1
. We confirm the strong dependence of the BLR wind velocity on the UV-to-X-ray continuum slope, the bolometric luminosity, and Eddington ratio. We infer BLR mass outflow rates in the range 0.005–3
M
⊙
yr
−1
, revealing a correlation with the bolometric luminosity consistent with that observed for ionised winds in the narrow line region (NLR), and X-ray winds detected in local AGNs, and kinetic power ∼10
−7
− 10
−4
×
L
Bol
. The coupling efficiencies predicted by AGN-feedback models are much higher than the values reported for the BLR winds in the SUPER sample; although it should be noted that only a fraction of the energy injected by the AGN into the surrounding medium is expected to become kinetic power in the outflow. Finally, we find an anti-correlation between the equivalent width of the OIII line and the CIV velocity shift, and a positive correlation between this latter parameter and OIII outflow velocity. These findings, for the first time in an unbiased sample of AGNs at
z
∼ 2, support a scenario where BLR winds are connected to galaxy-scale detected outflows, and are therefore capable of affecting the gas in the NLR located at kiloparsec scale distances.
ABSTRACT
We present the results of a new study investigating the relationship between observed Ly α equivalent width (Wλ(Ly α)) and the metallicity of the ionizing stellar population ( Z⋆) for a ...sample of 768 star-forming galaxies at 3 ≤ z ≤ 5 drawn from the VANDELS survey. Dividing our sample into quartiles of rest-frame Wλ(Ly α) across the range $-58 \,\rm {\mathring{\rm A}} \lesssim$Wλ(Ly α) $\lesssim 110 \,\rm {\mathring{\rm A}}$, we determine Z⋆ from full spectral fitting of composite far-ultraviolet spectra and find a clear anticorrelation between Wλ(Ly α) and Z⋆. Our results indicate that Z⋆ decreases by a factor ≳ 3 between the lowest Wλ(Ly α) quartile (〈Wλ(Ly α)$\rangle =-18\,\rm {\mathring{\rm A}}$) and the highest Wλ(Ly α) quartile (〈Wλ(Ly α)$\rangle =24\,\rm {\mathring{\rm A}}$). Similarly, galaxies typically defined as Lyman alpha emitters (LAEs; Wλ(Ly α) $\gt 20\,\rm {\mathring{\rm A}}$) are, on average, metal poor with respect to the non-LAE galaxy population (Wλ(Ly α) $\le 20\,\rm {\mathring{\rm A}}$) with Z⋆non-LAE ≳ 2 × Z⋆LAE. Finally, based on the best-fitting stellar models, we estimate that the increasing strength of the stellar ionizing spectrum towards lower Z⋆ is responsible for ${\simeq}15{-}25{{\ \rm per\ cent}}$ of the observed variation in Wλ(Ly α) across our sample, with the remaining contribution (${\simeq}75{-}85{{\ \rm per\ cent}}$) being due to a decrease in the H i/dust covering fractions in low- Z⋆ galaxies.
We present new ALMA observations aimed at mapping molecular gas reservoirs through the CO(3−2) transition in three quasars at z ≃ 2.4, LBQS 0109+0213, 2QZ J002830.4-281706, and HB89 0329-385. ...Previous Oiiiλ5007 observations of these quasars showed evidence for ionised outflows quenching star formation in their host galaxies. Systemic CO(3−2) emission has been detected only in one quasar, LBQS 0109+0213, where the CO(3−2) emission is spatially anti-correlated with the ionised outflow, suggesting that most of the molecular gas may have been dispersed or heated in the region swept by the outflow. In all three sources, including the one detected in CO, our constraints on the molecular gas mass indicate a significantly reduced reservoir compared to main-sequence galaxies at the same redshift, supporting a negative feedback scenario. In the quasar 2QZ J002830.4-281706, we tentatively detect an emission line blob blue-shifted by v ~ − 2000 km s-1 with respect to the galaxy systemic velocity and spatially offset by 0.2′′ (1.7 kpc) with respect to the ALMA continuum peak. Interestingly, such emission feature is coincident in both velocity and space with the ionised outflow as seen in Oiiiλ5007. This tentative detection must be confirmed with deeper observations but, if real, it could represent the molecular counterpart of the ionised gas outflow driven by the Active Galactic Nucleus (AGN). Finally, in all ALMA maps we detect the presence of serendipitous line emitters within a projected distance ~160 kpc from the quasars. By identifying these features with the CO(3−2) transition, we find that the serendipitous line emitters would be located within | Δv | < 500 km s-1 from the quasars, hence suggesting an overdensity of galaxies in two out of three quasars.
The stellar metallicity is a direct measure of the amount of metals present in a galaxy, since a large part of the metals lie in its stars. In this paper, we investigate new stellar metallicity ...indicators suitable for high-z galaxies by studying the stellar photospheric absorption lines in the rest-frame ultraviolet, hence sampling predominantly young hot stars. We defined these new indicators based on the equivalent widths (EW) of selected features using theoretical spectra created with the evolutionary population synthesis code Starburst99. We used them to compute the stellar metallicity for a sample of ultraviolet-selected galaxies at z > 3 from the AMAZE (Assessing the Mass-Abundance redshift Evolution) survey using very deep (37 h per object) VLT/FORS spectra. Moreover, we applied these new metallicity indicators to eight additional high redshift galaxies studied in literature. We then compared stellar and gas-phase metallicities measured from the emission lines for all these galaxies, finding that within the errors the two estimates are in good agreement, with possible tendency for stellar metallicities to be lower than the gas phase ones. For the first time, we study the stellar mass-stellar metallicity relation at z > 3. We find that the metallicity of young, hot stars in galaxies at z ~ 3 have similar values of the aged stars in local SDSS galaxies, in contrast to findings for the gas phase metallicity.
Abstract
We present adaptive optics assisted near-IR integral field spectroscopic observations of a luminous quasar at z = 2.4, previously observed as the first known example at high redshift of ...large-scale quasar-driven outflow quenching star formation in its host galaxy. The nuclear spectrum shows broad and blueshifted Hβ in absorption, which is tracing outflowing gas with high densities (>108–109 cm−3) and velocities in excess of 10 000 km s−1. The properties of the outflowing clouds (covering factor, density, column density and inferred location) indicate that they likely originate from the broad line region. The energetics of such nuclear regions is consistent with that observed in the large-scale outflow, supporting models in which quasar-driven outflows originate from the nuclear region and are energy conserving. We note that the asymmetric profile of both the Hβ and Hα emission lines is likely due to absorption by the dense outflowing gas along the line of sight. This outflow-induced asymmetry has implications on the estimation of the black hole mass using virial estimators, and warns about such effects for several other quasars characterized by similar line asymmetries. More generally, our findings may suggest a broader revision of the decomposition and interpretation of quasar spectral features, in order to take into account the presence of potential broad blueshifted Balmer absorption lines. Our high spatial resolution data also reveal redshifted nebular emission lines, which could be potentially tracing an inflowing stream.
Gamma-ray bursts (GRBs) have been separated into two classes, originally along the lines of duration and spectral properties, called 'short/hard' and 'long/soft.' The latter have been conclusively ...linked to the explosive deaths of massive stars, while the former are thought to result from the merger or collapse of compact objects. In recent years, indications have been accumulating that the short/hard versus long/soft division does not map directly onto what would be expected from the two classes of progenitors, leading to a new classification scheme called Type I and Type II which is based on multiple observational criteria. We use a large sample of GRB afterglow and prompt-emission data (adding further GRB afterglow observations in this work) to compare the optical afterglows (or the lack thereof) of Type I GRBs with those of Type II GRBs. In comparison to the afterglows of Type II GRBs, we find that those of Type I GRBs have a lower average luminosity and show an intrinsic spread of luminosities at least as wide. From late and deep upper limits on the optical transients, we establish limits on the maximum optical luminosity of any associated supernova (SN), confirming older works and adding new results. We use deep upper limits on Type I GRB optical afterglows to constrain the parameter space of possible mini-SN emission associated with a compact-object merger. Using the prompt-emission data, we search for correlations between the parameters of the prompt emission and the late optical afterglow luminosities. We find tentative correlations between the bolometric isotropic energy release and the optical afterglow luminosity at a fixed time after the trigger (positive), and between the host offset and the luminosity (negative), but no significant correlation between the isotropic energy release and the duration of the GRBs. We also discuss three anomalous GRBs, GRB 060505, GRB 060614, and GRB 060121, in light of their optical afterglow luminosities.
Aims. The aim of this paper is to test the basic model of negative active galactic nuclei (AGN) feedback. According to this model, once the central black hole accretes at the Eddington limit and ...reaches a certain critical mass, AGN driven outflows blow out gas, suppressing star formation in the host galaxy and self-regulating black hole growth. Methods. We consider a sample of 224 quasars selected from the Sloan Digital Sky Survey (SDSS) at z< 1 observed in the infrared band by the Herschel Space Observatory in point source photometry mode. We evaluate the star formation rate in relation to several outflow signatures traced by the O III λ4959, 5007 and O II λ3726, 3729 emission lines in about half of the sample with high quality spectra. Results. Most of the quasars show asymmetric and broad wings in O III, which we interpret as outflow signatures. We separate the quasars in two groups, “weakly” and “strongly” outflowing, using three different criteria. When we compare the mean star formation rate in five redshift bins in the two groups, we find that the star formation rate (SFR) are comparable or slightly larger in the strongly outflowing quasars. We estimate the stellar mass from spectral energy distribution (SED) fitting and the quasars are distributed along the star formation main sequence, although with a large scatter. The scatter from this relation is uncorrelated with respect to the kinematic properties of the outflow. Moreover, for quasars dominated in the infrared by starburst or by AGN emission, we do not find any correlation between the star formation rate and the velocity of the outflow, a trend previously reported in the literature for pure starburst galaxies. Conclusions. We conclude that the basic AGN negative feedback scenario seems not to agree with our results. Although we use a large sample of quasars, we did not find any evidence that the star formation rate is suppressed in the presence of AGN driven outflows on large scale. A possibility is that feedback is effective over much longer timescales than those of single episodes of quasar activity.
The supernova rate per unit mass Mannucci, F.; Della Valle, M.; Panagia, N. ...
Astronomy and astrophysics (Berlin),
04/2005, Letnik:
433, Številka:
3
Journal Article
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We compute the rate of supernovae (SNe) of different types along the Hubble sequence normalized to the near-infrared luminosity and to the stellar mass of the parent galaxies. This is made possible ...by the new complete catalog of near-infrared galaxy magnitudes obtained by 2MASS. We find that the rates of all SN types, including Ia, Ib/c and II, show a sharp dependence on both the morphology and the ($B-K$) colors of the parent galaxies and, therefore, on the star formation activity. In particular we find, with a high statistical significance, that the type Ia rate in late type galaxies is a factor ~20 higher than in E/S0. Similarly, the type Ia rate in the galaxies bluer than $B-K=2.6$ is about a factor of 30 larger than in galaxies with $B-K>4.1$. These findings can be explained by assuming that a significant fraction of Ia events in late spirals/irregulars originates in a relatively young stellar component.
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