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We investigated the stellar population properties of a sample of 1858 massive compact galaxies (MCGs) extracted from the Sloan Digital Sky Survey (SDSS). Motivated by previous results showing that older compact galaxies tend to have larger velocity dispersion at fixed stellar mass, we used the distance to the σe versus R e and M ⋆ versus σe relations as selection criteria. We found that MCGs are old (≳10 Gyr), α-enhanced ([α/Fe] ∼ 0.2), and have solar to supersolar stellar metallicities. Metallicity increases with σe, while age and [α/Fe] do not vary significantly. Moreover, at fixed σe, metallicity and stellar mass are correlated. Compared with a control sample of typical quiescent galaxies, MCGs have, on average, lower metallicities than control sample galaxies (CSGs) of similar σe. For σe ≲ 225 km s−1, MCGs are older and more α-enhanced than CSGs, while for higher σe ages and α-enhancement are similar. The differences in age and α-enhancement can be explained by lower σe CSGs being an amalgam of quiescent galaxies with a variety of ages. The origin of the differences in metallicity, however, is not clear. Lastly, we compared the stellar mass within the region probed by the SDSS fibre finding that, at fixed fibre velocity dispersion, MCGs have lower stellar masses on average. Since the velocity dispersion is a tracer of the dynamical mass, this raises the possibility that MCGs have, on average, a bottom-heavier initial mass function or a larger dark matter fraction within the inner ∼1−2 kpc. [ABSTRACT FROM AUTHOR]

Compact groups of dwarf galaxies (CGDs) have been observed at low redshifts (z < 0.1) and are direct evidence of hierarchical assembly at low masses. To understand the formation of CGDs and the galaxy assembly in the low-mass regime, we search for analogues of compact (radius ≤100 kpc) groups of dwarfs (7 ≤ log [ M */M⊙] ≤ 9.5) in the IllustrisTNG highest resolution simulation. Our analysis shows that TNG50-1 can successfully produce CGDs at z  = 0 with realistic total and stellar masses. We also find that the CGD number density decreases towards the present, especially at z ≲ 0.26, reaching |$n \approx 10^{-3.5} \ \rm cMpc^{-3}$| at z  = 0. This prediction can be tested observationally with upcoming surveys targeting the faint end of the galaxy population and is essential to constrain galaxy evolution models in the dwarf regime. The majority of simulated groups at z ∼ 0 formed recently (⁠|$\lesssim 1.5 \ \rm Gyr$|⁠), and CGDs identified at z ≤ 0.5 commonly take more than 1 Gyr to merge completely, giving origin to low- to intermediate-mass (8 ≤ log [ M */M⊙] ≤ 10) normally star-forming galaxies at z  = 0. We find that haloes hosting CGDs at z  = 0 formed later when compared to haloes of similar mass, having lower stellar masses and higher total gas fractions. The simulations suggest that CGDs observed at z ∼ 0 arise from a late hierarchical assembly in the last ∼3 Gyr, producing rapid growth in total mass relative to stellar mass and creating dwarf groups with median halo masses of |$\sim 10^{11.3} \ \rm M_\odot$| and B -band mass-to-light ratios mostly in the range 10 ≲ M / L ≲ 100, in agreement with previous theoretical and observational studies. [ABSTRACT FROM AUTHOR]

We investigate the formation and evolution of z = 0 massive compact galaxies (MCGs) in the IllustrisTNG cosmological simulation. We found that, as in observations, MCGs are mainly old (median age ∼10.8 Gyr), have supersolar metallicities (median log  Z /Z⊙ ∼ 0.35), and are α-enhanced (median [α/Fe] ∼ 0.25). The age distribution extends to younger ages, however, and a few MCGs are as young as ∼7 Gyr. In general, MCGs assemble their mass early and accrete low angular momentum gas, significantly increasing their mass while growing their size much slower. A small fraction of MCGs follow another evolutionary path, going through a compaction event, with their sizes shrinking by 40 per cent or more. The accretion of low angular momentum gas leads to enhanced supermassive black hole (SMBH) growth, and MCGs reach the threshold SMBH mass of |$\log M_\mathrm{BH}\sim 10^{8.5}\ \mathrm{ M}_\odot$| – when kinetic active galactic nucleus feedback kicks in and quenches the galaxy – earlier than non-compact galaxies. Comparing MCGs to a sample of median-sized quiescent galaxies matched in effective velocity dispersion, we find that their accretion histories are very different. 71 per cent of MCGs do not merge after quenching compared to 37 per cent of median-sized quiescent galaxies. Moreover, tracing these populations back in time, we find that at least a third of median-sized quiescent galaxies do not have a compact progenitor, underscoring that both dry mergers and progenitor bias effects are responsible for the differences in the kinematics and stellar population properties of MCGs and median-sized quiescent galaxies. [ABSTRACT FROM AUTHOR]

We characterized the kinematics, morphology, and stellar population (SP) properties of a sample of massive compact quiescent galaxies (MCGs, |$10\, \lesssim \, \log M_\star$| /M |$_\odot \, \lesssim \, 11$| and r e ∼ 1–3 kpc) in the MaNGA Survey, with the goal of constraining their formation, assembly history, and assessing their relation with non-compact quiescent galaxies. We compared their properties with those of a control sample of median-sized quiescent galaxies (r e ∼ 4–8 kpc) with similar effective velocity dispersions. MCGs have elevated rotational support, as evidenced by a strong anticorrelation between the Gauss–Hermite moment h 3 and V / σ. In contrast, 30 |${{\ \rm per\ cent}}$| of control sample galaxies (CSGs) are slow rotators, and fast-rotating CSGs generally show a weak h 3– V / σ anticorrelation. MCGs and CSGs have similar ages, but MCGs are more metal-rich and α -enhanced. Both MCGs and CSGs have shallow negative metallicity gradients and flat [ α /Fe] gradients. On average, MCGs and CSGs have flat age gradients, but CSGs have a significantly larger dispersion of gradient values. The kinematics and SP properties of MCGs suggest that they experienced highly dissipative gas-rich events, such as mergers, followed by an intense, short, and centrally concentrated burst of star formation, between 4 and 10 Gyr ago (z ∼ 0.4–2), and had a quiet accretion history since then. This sequence of events might be analogous to, although less extreme than, the compaction events that formed compact quiescent galaxies at z  ∼ 2. The small sizes of MCGs, and the high efficiency and short duration of their last star formation episode suggest that they are descendants of compact post-starburst galaxies. [ABSTRACT FROM AUTHOR]

In order to gauge the role that active galactic nuclei play in the evolution of galaxies via the effect of kinetic feedback in nearby QSO 2's (z ∼ 0.3), we observed eight such objects with bolometric luminosities |$L_{bol} \sim 10^{46}\rm {erg\, s^{-1}}$| using Gemini Multi-Object Spectrograph-integral field units. The emission lines were fitted with at least two Gaussian curves, the broadest of which we attributed to gas kinetically disturbed by an outflow. We found that the maximum extent of the outflow ranges from ∼1 to 8 kpc, being |${\sim }\, 0.5\, {\pm }\, 0.3$| times the extent of the [ |$\mathrm{O\,{\small III}}$| ] ionized gas region. Our ' default ' assumptions for the gas density (obtained from the [ |$\mathrm{S\,{\small II}}$| ] doublet) and outflow velocities resulted in peak mass outflow rates of |$\dot{M}_{\mathrm{ out}}^{{\tt def}}\sim$|  3–30  |$\rm {M_{\odot }}\, yr^{-1}$| and outflow power of |$\dot{E}_{\mathrm{ out}}^{{\tt \mathrm{ def}}}\sim \, 10^{41}$| – |$10^{43}\, \mathrm{erg\, s^{-1}}$|⁠. The corresponding kinetic coupling efficiencies are |$\varepsilon _f^{{\tt def}}=\dot{E}_{\mathrm{ out}}^{{\tt def}}/L_{\mathrm{ bol}}\, \sim 7\times 10^{-4}$| –0.5 per cent, with the average efficiency being only 0.06 per cent (0.01 per cent median), implying little feedback powers from ionized gas outflows in the host galaxies. We investigated the effects of varying assumptions and calculations on |$\dot{M}_{\mathrm{ out}}$| and |$\dot{E}_{\mathrm{ out}}$| regarding the ionized gas densities, velocities, masses, and inclinations of the outflow relative to the plane of the sky, resulting in average uncertainties of 1 dex. In particular, we found that better indicators of the [ |$\mathrm{O\,{\small III}}$| ] emitting gas density than the default [ |$\mathrm{S\,{\small II}}$| ] line ratio, such as the [ |$\mathrm{Ar\,{\small IV}}$| ] λλ4711,40 line ratio, result in almost an order of magnitude decrease in the ε f . [ABSTRACT FROM AUTHOR]

We analyse the globular cluster (GC) systems of a sample of 15 massive, compact early-type galaxies (ETGs), 13 of which have already been identified as good relic galaxy candidates on the basis of their compact morphologies, old stellar populations and stellar kinematics. These relic galaxy candidates are likely the nearby counterparts of high-redshift red nugget galaxies. Using F814W (≈ I) and F160W (≈ H) data from the WFC3 camara onboard the Hubble Space Telescope , we determine the total number, luminosity function, specific frequency, colour, and spatial distribution of the GC systems (GCSs). We find lower specific frequencies (SN < 2.5 with a median of SN = 1) than ETGs of comparable mass. This is consistent with a scenario of rapid, early dissipative formation, with relatively low levels of accretion of low-mass, high- SN satellites. The GC half-number radii are compact, but follow the relations found in normal ETGs. We identify an anticorrelation between the specific angular momentum (λ R) of the host galaxy and the (I − H) colour distribution width of their GCSs. Assuming that λ R provides a measure of the degree of dissipation in massive ETGs, we suggest that the (I − H) colour distribution width can be used as a proxy for the degree of complexity of the accretion histories in these systems. [ABSTRACT FROM AUTHOR]

NGC 3393, a nearby Seyfert 2 galaxy with nuclear radio jets, large-scale and nuclear bars, and a posited secondary supermassive black hole, provides an interesting laboratory to test the physics of inflows and outflows. Here we present and analyse the molecular gas [ALMA observations of CO J:2-1 emission over a field of view (FOV) of 45 arcsec × 45 arcsec, at 0 $${^{\prime\prime}_{.}}$$ 56 (143 pc) spatial and 5 km s−1 spectral resolution), ionized gas and stars (GEMINI–GMOS/IFU; over an FOV of 4 arcsec × 5 arcsec, at 0 $${^{\prime\prime}_{.}}$$ 62 (159 pc) spatial and 23 km s−1 spectral resolution) in NGC 3393. The ionized gas emission, detected over the complete GEMINI–GMOS FOV, has three identifiable kinematic components. A narrow (σ < 115 km s−1) component present in the complete FOV, which is consistent with rotation in the galaxy disc. A broad (σ > 115 km s−1) redshifted component, detected near the NE and SW radio lobes; which we interpret as a radio jet-driven outflow. And a broad (σ > 115 km s−1) blueshifted component that shows high velocities in a region perpendicular to the radio jet axis; we interpret this as an equatorial outflow. The CO J:2-1 emission is detected in spiral arms on 5–20 arcsec scales, and in two disturbed circumnuclear regions. The molecular kinematics in the spiral arms can be explained by rotation. The highly disturbed kinematics of the inner region can be explained by perturbations induced by the nuclear bar and interactions with the large scale bar. We find no evidence for, but cannot strongly rule out, the presence of the posited secondary black hole. [ABSTRACT FROM AUTHOR]

We use optical spectra from the inner 1.8×2.5 kpc² of the Seyfert 2 galaxy NGC1358, obtained with the GMOS integral field spectrograph on the Gemini South telescope at a spatial resolution of ≈165 pc, to assess the feeding and feedback processes in this nearby active galaxy. Five gaseous kinematical components are observed in the emission line profiles. One of the components is present in the entire field-of-view and we interpret it as due to gas rotating in the disc of the galaxy. Three of the remaining components we interpret as associated with active galactic nucleus (AGN) feedback: a compact unresolved outflow in the inner 1 arcsec and two gas clouds observed at opposite sides of the nucleus, which we propose have been ejected in a previous AGN burst. The disc component velocity field is strongly disturbed by a large-scale bar. The subtraction of a velocity model combining both rotation and bar flows reveals three kinematic nuclear spiral arms: two in inflow and one in outflow. We estimate the mass inflow rate in the inner 180 pc obtaining Min ≈1.5×10-2⊙ yr-1, about 160 times larger than the accretion rate necessary to power this AGN. [ABSTRACT FROM AUTHOR]

We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report new arcsec resolution observations of HCN (1-0) and HCO+ (1-0) for three objects. In NGC 3079, the lines show complex profiles as a result of self-absorption and saturated continuum absorption. H13CN reveals the continuum absorption profile, with a peak close to the galaxy's systemic velocity that traces disc rotation, and a second feature with a blue wing extending to -350 km s-1 that most likely traces a nuclear outflow. The morphological and spectral properties of the emission lines allow us to constrain the dense gas dynamics. We combine our kinematic analysis for these three objects, as well as another with archival data, with a previous comparable analysis of four other objects, to create a sample of eight Seyferts. In seven of these, the emission line kinematics imply thick disc structures on radial scales of ~100 pc, suggesting such structures are a common occurrence. We find a relation between the circum-nuclear LHCN and Mdyn that can be explained by a gas fraction of 10 per cent and a conversion factor αHCN ~ 10 between gas mass and HCN luminosity. Finally, adopting a different perspective to probe the physical properties of the gas around active galactic nuclei, we report on an analysis of molecular line ratios which indicates that the clouds in this region are not self-gravitating. [ABSTRACT FROM AUTHOR]

We present two-dimensional gaseous kinematics of the inner 1.2 × 1.8 kpc2 of the Seyfert 2 galaxy NGC 3081, from optical spectra (5600-7000 Å) obtained with the Gemini Multi Object Spectrograph integral field spectrograph on the Gemini North telescope at a spatial resolution of ≈100 pc.We have identified two components in the line emitting gas. A narrower component (full width at half-maximum, FWHM ≈ 60-100 km s-1), which appears to be gas in the galaxy disc, and which shows a distorted rotation pattern, is observed over the whole field of view. A broader component (FWHM ≈ 150-250 km s-1) is present in the inner ≈2 arcsec (200 pc) and shows blueshifts and redshifts in the near and far sides of the galaxy, respectively, consistent with a bipolar outflow. Assuming this to be the case, we estimate that the mass outflow rate in ionized gas(Mout) is between 1.9 ×10-3 and 6.9 ×10-3 M☉ yr-1. The subtraction of a rotation model from the narrower component velocity field reveals a pattern of excess blueshifts of ≈50 km s-1 in the far side of the galaxy and similar excess redshifts in the near side, which are cospatial with a previously known nuclear bar.We interpret these residuals as due to gas following non-circular orbits in the barred potential. Under the assumption that these motions may lead to gas inflows, we estimate an upper limit for the mass inflow rate in ionized gas of ϕ ≈ 1.3 ×10-2 M☉ yr-1. [ABSTRACT FROM AUTHOR]

We describe a complete volume limited sample of nearby active galaxies selected by their 14–195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We also describe a complementary sample of inactive galaxies, selected to match the host galaxy properties. The active sample appears to have no bias in terms of active galactic nucleus (AGN) type, the only difference being the neutral absorbing column, which is two orders of magnitude greater for the Seyfert 2s. In the luminosity range spanned by the sample, –43.7, the optically obscured and X-ray absorbed fractions are 50%–65%. The similarity of these fractions to more distant spectroscopic AGN samples, although over a limited luminosity range, suggests that the torus does not strongly evolve with redshift. Our sample confirms that X-ray unabsorbed Seyfert 2s are rare, comprising not more than a few percent of the Seyfert 2 population. At higher luminosities, the optically obscured fraction decreases (as expected for the increasing dust sublimation radius), but the X-ray absorbed fraction changes little. We argue that the cold X-ray absorption in these Seyfert 1s can be accounted for by neutral gas in clouds that also contribute to the broad-line region (BLR) emission, and suggest that a geometrically thick neutral gas torus co-exists with the BLR and bridges the gap to the dusty torus. [ABSTRACT FROM AUTHOR]