- ID:
- ivo://CDS.VizieR/J/A+A/524/A6
- Title:
- Evolution of spectral early-type galaxies
- Short Name:
- J/A+A/524/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the evolution of spectral early-type galaxies in clusters, groups, and the field up to redshift 0.9 using the ESO Distant Cluster Survey (EDisCS) dataset. We measure structural parameters (circularized half-luminosity radii Re, surface brightness Ie, and velocity dispersions sigma) for 154 cluster and 68 field galaxies. On average, we achieve precisions of 10% in Re, 0.1dex in logIe, and 10% in sigma. We sample ~20% of cluster and ~10% of field spectral early-type galaxies to an I band magnitude in a 1arcsec radius aperture as faint as I1=22. We study the evolution of the zero point of the fundamental plane (FP) and confirm results in the literature, but now also for the low cluster velocity dispersion regime.
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- ID:
- ivo://CDS.VizieR/J/A+A/659/A40
- Title:
- Evolving dark matter profiles since z<=1
- Short Name:
- J/A+A/659/A40
- Date:
- 02 Mar 2022 08:01:11
- Publisher:
- CDS
- Description:
- In the concordance cosmological scenario, the cold collisionless dark matter component dominates the mass budget of galaxies and interacts with baryons only via gravity. However, there is growing evidence that the former, instead, responds to the baryonic (feedback) processes by modifying its density distribution. These processes can be captured by comparing the inner dynamics of galaxies across cosmic time. We present a pilot study of dynamical mass modeling of high redshift galaxy rotation curves, which is capable of constraining the structure of dark matter halos across cosmic time. We investigate the dark matter halos of 256 star-forming disk-like galaxies at z~1 using the KMOS Redshift One Spectroscopic Survey (KROSS). This sample covers the redshifts 0.6<=z<=1.04, effective radii 0.69<=Re[kpc]<=7.76, and total stellar masses 8.7<=log(Mstar [M])<=11.32. We present a mass modeling approach to study the rotation curves of these galaxies, which allow us to dynamically calculate the physical properties associated with the baryons and the dark matter halo. For the former we assume a Freeman disk, while for the latter we employ the NFW (cusp) and the Burkert (cored) halo profiles, separately. At the end, we compare the results of both cases with state-of-the-art galaxy simulations (EAGLE, TNG100, and TNG50). We find that the "cored" dark matter halo emerged as the dominant quantity from a radius 1-3 times the effective radius. Its fraction to the total mass is in good agreement with the outcome of hydrodynamical galaxy simulations. Remarkably, we found that the dark matter core of z~1 star-forming galaxies are smaller and denser than their local counterparts. Dark matter halos have gradually expanded over the past 6.5Gyrs. That is, observations are capable of capturing the dark matter response to the baryonic processes, thus giving us the first piece of empirical evidence of "gravitational potential fluctuations" in the inner region of galaxies that can be verified with deep surveys and future missions.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/74
- Title:
- EW measurements of 6 Segue 1 red giants
- Short Name:
- J/ApJ/786/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Magellan/MIKE and Keck/HIRES high-resolution spectra of six red giant stars in the dwarf galaxy Segue 1. Including one additional Segue 1 star observed by Norris et al. (2010ApJ...722L.104N), high-resolution spectra have now been obtained for every red giant in Segue 1. Remarkably, three of these seven stars have metallicities below [Fe/H]=-3.5, suggesting that Segue 1 is the least chemically evolved galaxy known. We confirm previous medium-resolution analyses demonstrating that Segue 1 stars span a metallicity range of more than 2 dex, from [Fe/H]=-1.4 to [Fe/H]=-3.8. All of the Segue 1 stars are {alpha}-enhanced, with [{alpha}/Fe]~0.5. High {alpha}-element abundances are typical for metal-poor stars, but in every previously studied galaxy [{alpha}/Fe] declines for more metal-rich stars, which is typically interpreted as iron enrichment from supernova Ia. The absence of this signature in Segue 1 indicates that it was enriched exclusively by massive stars. Other light element abundance ratios in Segue 1, including carbon enhancement in the three most metal-poor stars, closely resemble those of metal-poor halo stars. Finally, we classify the most metal-rich star as a CH star given its large overabundances of carbon and s-process elements. The other six stars show remarkably low neutron-capture element abundances of [Sr/H]<-4.9 and [Ba/H]<-4.2, which are comparable to the lowest levels ever detected in halo stars. This suggests minimal neutron-capture enrichment, perhaps limited to a single r-process or weak s-process synthesizing event. Altogether, the chemical abundances of Segue 1 indicate no substantial chemical evolution, supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/761
- Title:
- EWs of metal-poor stars in the UMi I dSph galaxy
- Short Name:
- J/MNRAS/449/761
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed chemical element abundance ratios of 17 elements with eight<=Z<=60 in three metal-poor stars in the Ursa Minor dwarf spheroidal galaxy, which we combine with extant data from the literature to assess the predictions of a novel suite of galaxy chemical evolution models. The spectroscopic data were obtained with the Keck/High-Resolution Echelle Spectrograph instrument and revealed low metallicities of [Fe/H]=-2.12, -2.13 and -2.67 dex. While the most metal-poor star in our sample shows an overabundance of [Mn/Fe] and other Fe-peak elements, our overall findings are in agreement with previous studies of this galaxy: elevated values of the [{alpha}/Fe] ratios that are similar to, or only slightly lower than, the halo values but with SN Ia enrichment at very low metallicity, as well as an enhancement of the ratio of first to second peak neutron capture elements [Y/Ba] with decreasing metallicity. The chemical evolution models which were tailored to reproduce the metallicity distribution function of the dwarf spheroidal, indicate that Ursa Minor had an extended star formation which lasted nearly 5 Gyr with low efficiency and are able to explain the [Y/Ba] enhancement at low metallicity for the first time. In particular, we show that the present-day lack of gas is probably due to continuous loss of gas from the system, which we model as winds.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/11
- Title:
- Exploring 6 AGN dusty torus models. II.
- Short Name:
- J/ApJ/884/11
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers devoted to exploring a set of six dusty models of active galactic nuclei (AGN) with available spectral energy distributions. These models are the smooth torus by Fritz+ (2006MNRAS.366..767F), the clumpy torus by Nenkova+ (2008ApJ...685..147N and 2008ApJ...685..160N), the clumpy torus by Honig & Kishimoto (2010A&A...523A..27H), the two-phase torus by Siebenmorgen+ (2015A&A...583A.120S), the two-phase torus by Stalevski+ (2012MNRAS.420.2756S and 2016MNRAS.458.2288S), and the wind model by Honig & Kishimoto (2017ApJ...838L..20H). The first paper explores discrimination among models and the parameter restriction using synthetic spectra. Here we perform spectral fitting of a sample of 110 AGN drawn from the Swift/BAT survey with Spitzer/IRS spectroscopic data. The aim is to explore which is the model that describes better the data and the resulting parameters. The clumpy wind-disk model by Honig & Kishimoto provides good fits for ~50% of the sample, and the clumpy torus model by Nenkova+ is good at describing ~30% of the objects. The wind-disk model by Honig & Kishimoto is better for reproducing the mid-infrared spectra of type 1 Seyferts (with 60% of the type 1 Seyferts well reproduced by this model compared to the 10% well represented by the clumpy torus model by Nenkova+), while type 2 Seyferts are equally fitted by both models (roughly 40% of the type 2 Seyferts). Large residuals are found irrespective of the model used, indicating that the AGN dust continuum emission is more complex than predicted by the models or that the parameter space is not well sampled. We found that all the resulting parameters for our AGN sample are roughly constrained to 10%-20% of the parameter space. Contrary to what is generally assumed, the derived outer radius of the torus is smaller (reaching up to a factor of ~5 smaller for 10pc tori) for the smooth torus by Fritz+ and the two-phase torus by Stalevski+ than the one derived from the clumpy torus by Nenkova+ Covering factors and line-of-sight viewing angles strongly depend on the model used. The total dust mass is the most robust derived quantity, giving equivalent results for four of these models.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A51
- Title:
- Extended CO structures in NGC6240
- Short Name:
- J/A+A/549/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep CO(1-0) observations of NGC6240 performed with the IRAM Plateau de Bure Interferometer (PdBI). NGC6240 is the prototypical example of a major galaxy merger in progress, caught at an early stage, with an extended, strongly-disturbed butterfly- like morphology and a heavily obscured active nucleus in the core of each progenitor galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/3263
- Title:
- Extended galaxy halo gas through HI and OVI
- Short Name:
- J/MNRAS/449/3263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of extended galaxy halo gas through HI and OVI absorption over two decades in projected distance at z~0.2. The study is based on a sample of 95 galaxies from a highly complete (>80 percent) survey of faint galaxies (L>0.1L*) with archival quasar absorption spectra and 53 galaxies from the literature. A clear anticorrelation is found between HI (OVI) column density and virial radius normalized projected distance, d/Rh. Strong HI (OVI) absorption systems with column densities greater than 10^14.0^ (10^13.5^)cm^-2^ are found for 48 of 54 (36 of 42) galaxies at d<Rh indicating a mean covering fraction of <{kappa}_HI_>=0.89 (<{kappa}_OVI_>=0.86). OVI absorbers are found at d~Rh, beyond the extent observed for lower ionization species. At d/Rh=1-3 strong HI (OVI) absorption systems are found for only 7 of 43 (5 of 34) galaxies (<{kappa}_HI_>=0.16 and <{kappa}_OVI_>=0.15). Beyond d=3Rh, the HI and OVI covering fractions decrease to levels consistent with coincidental systems. The high completeness of the galaxy survey enables an investigation of environmental dependence of extended gas properties. Galaxies with nearby neighbours exhibit a modest increase in Ovi covering fraction at d>Rh compared to isolated galaxies (<{kappa}_OVI_~0.13 versus 0.04) but no excess HI absorption. These findings suggest that environmental effects play a role in distributing heavy elements beyond the enriched gaseous haloes of individual galaxies. Finally, we find that differential HI and OVI absorption between early- and late-type galaxies continues from d<Rh to d~3Rh.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A74
- Title:
- Extended main-sequence turn-offs isochrones
- Short Name:
- J/A+A/632/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extended main-sequence turn-offs (eMSTO) are a commonly observed property of young clusters. A global theoretical interpretation for the eMSTOs is still lacking, but stellar rotation is considered a necessary ingredient to explain the eMSTO. We aim to assess the importance of core-boundary and envelope mixing in stellar interiors for the interpretation of eMSTOs in terms of one coeval population. We construct isochrone-clouds based on interior mixing profiles of stars with a convective core calibrated from asteroseismology of isolated galactic field stars. We fit these isochrone-clouds to the measured eMSTO to estimate the age and core mass of the stars in the two young clusters NGC 1850 and NGC 884, assuming one coeval population and fixing the metallicity to the one measured from spectroscopy. We assess the correlations between the interior mixing properties of the cluster members and their rotational and pulsational properties. We find that stellar models based on asteroseismically-calibrated interior mixing profiles lead to enhanced core masses of eMSTO stars and can explain a good fraction of the observed eMSTOs of the two considered clusters in terms of one coeval population of stars, with similar ages to those in the literature, given the large uncertainties. The rotational and pulsational properties of the stars in NGC 884 are not sufficiently well known to perform asteroseismic modelling, as it is achieved for field stars from space photometry. The stars in NGC 884 for which we have vsini and a few pulsation frequencies show no correlation between these properties and the core masses of the stars that set the cluster age. Future cluster space asteroseismology may allow to interpret the values of the core masses in terms of the physical processes that cause them, based on the modelling of the interior mixing profiles for the individual member stars with suitable identified modes.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A65
- Title:
- Extended stellar objects in galaxies
- Short Name:
- J/A+A/547/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the last decade, very extended old stellar clusters with masses in the range from a few 10^4^ to 10^8^M_{sun}_ and effective radii larger than 10pc have been found in various types of galaxies in different environments. Objects with masses comparable to normal globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). The paper analyses the observational parameters total luminosity, M_V_, effective radius, r_eff_, and projected distance to the host galaxy, R_proj_, of all known ECs and UCDs and the dependence of these parameters on the type and the total luminosity of their host galaxy. We searched the available literature to compile a catalog of star clusters with effective radii larger than 10pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects - abbreviated "EOs" - in this paper. In total, we found 813 EOs of which 171 are associated with late-type galaxies and 642 EOs associated with early-type galaxies. EOs cover a luminosity range from about M_V_=-4 to -14mag. However, the vast majority of EOs brighter than M_V_=-10mag are associated with giant elliptical galaxies. At each magnitude extended objects are found with effective radii between 10pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the EO luminosity functions peak at -6.40mag and -6.47mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r_eff_ vs. M_V_ parameter space, while there is a clear gap between EOs and early type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of some compact elliptical galaxies. We compare the EO sample with the numerical models of a previous paper and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged star clusters of cluster complexes (CCs).
- ID:
- ivo://CDS.VizieR/J/AJ/155/46
- Title:
- Extragalactic candidates in the VVV survey
- Short Name:
- J/AJ/155/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for extragalactic sources in the VISTA Variables in the Via Lactea survey that are hidden by the Galaxy. Herein, we describe our photometric procedure to find and characterize extragalactic objects using a combination of SExtractor and PSFEx. It was applied in two tiles of the survey: d010 and d115, without previous extragalactic IR detections, in order to obtain photometric parameters of the detected sources. The adopted criteria to define extragalactic candidates include CLASS_STAR<0.3; 1.0<R_1/2_<5.0 arcsec; 2.1<C<5; and {Phi}>0.002 and the colors: 0.5<(J-K_s_)<2.0 mag; 0.0<(J-H)<1.0 mag; 0.0<(H-K_s_)<2.0 mag and (J-H)+0.9(H-K_s_)>0.44 mag. We detected 345 and 185 extragalactic candidates in the d010 and d115 tiles, respectively. All of them were visually inspected and confirmed to be galaxies. In general, they are small and more circular objects, due to the near-IR sensitivity to select more compact objects with higher surface brightness. The procedure will be used to identify extragalactic objects in other tiles of the VVV disk, which will allow us to study the distribution of galaxies and filaments hidden by the Milky Way.