- ID:
- ivo://CDS.VizieR/J/MNRAS/441/203
- Title:
- Massive quiescent ETG in clusters
- Short Name:
- J/MNRAS/441/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the mass-size relation of ~400 quiescent massive ETGs (M*/M_{sun}_>3x10^10^) hosted by massive clusters (M200~2-7x10^14^M_{sun}_) at 0.8<z<1.5, compared to those found in the field at the same epoch. Size is parametrized using the mass-normalized B-band rest-frame size, {gamma}=R_e_/M_11_^0.57^. We find that the {gamma} distributions in both environments peak at the same position, but the distributions in clusters are more skewed towards larger sizes. This tail induces average sizes ~ 30-40 percent larger for cluster galaxies than for field galaxies of similar stellar mass, while the median sizes are statistically the same with a difference of ~10+/-10%. Since this size difference is not observed in the local Universe, the evolution of average galaxy size at fixed stellar mass from z~1.5 for cluster galaxies is less steep at more than 3{sigma}({prop.to}(1+z)-0.53+/-0.04) than the evolution of field galaxies ({prop.to}(1+z)-0.92+/-0.04). The difference in evolution is not measured when the median values of {gamma} are considered: {prop.to}(1+z)-0.84+/-0.04 in the field versus {prop.to}(1+z)-0.71+/-0.05 in clusters. In our sample, the tail of large galaxies is dominated by galaxies with 3x10^10^<M*/M_{sun}_<10^11^. At this low-mass end, the difference in the average size is better explained by the accretion of new galaxies that are quenched more efficiently in clusters and/or by different morphological mixing in the cluster and field environments. If part of the size evolution would be due to mergers, the difference that we see between cluster and field galaxies could be caused by higher merger rates in clusters at higher redshift, when galaxy velocities are lower.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/3743
- Title:
- 104 massive quiescent galaxies SFHs
- Short Name:
- J/MNRAS/457/3743
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present star formation histories (SFHs) for a sample of 104 massive (stellar mass M>10^10^M_{sun}_) quiescent galaxies (MQGs) at z=1.0-1.5 from the analysis of spectrophotometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) and HST/WFC3 G102 and G141 surveys of the GOODS-North field, jointly with broad-band observations from ultraviolet (UV) to far-infrared (far-IR). The sample is constructed on the basis of rest-frame UVJ colours and specific star formation rates (sSFRs=SFR/Mass). The spectral energy distributions (SEDs) of each galaxy are compared to models assuming a delayed exponentially declining SFH. A Monte Carlo algorithm characterizes the degeneracies, which we are able to break taking advantage of the SHARDS data resolution, by measuring indices such as MgUV and D4000. The population of MQGs shows a duality in their properties. The sample is dominated (85 per cent) by galaxies with young mass-weighted ages, <t_M_><2Gyr, short star formation time-scales, <{tau}>~60-200MYr, and masses log(M/M_{sun}_)~10.5. There is an older population (15 per cent) with <t_M_>=2-4Gyr, longer star formation time-scales, <{tau}>~400Myr, and larger masses, log(M/M_{sun}_)~10.7. The SFHs of our MQGs are consistent with the slope and the location of the main sequence of star-forming galaxies at z>1.0, when our galaxies were 0.5-1.0Gyr old. According to these SFHs, all the MQGs experienced a luminous infrared galaxy phase that lasts for ~500Myr, and half of them an ultraluminous infrared galaxy phase for ~100Myr. We find that the MQG population is almost assembled at z~1, and continues evolving passively with few additions to the population.
- ID:
- ivo://CDS.VizieR/J/AJ/101/1408
- Title:
- Massive stars in Cyg OB2.
- Short Name:
- J/AJ/101/1408
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The galactic association Cygnus OB2, which contains heavily reddened O and B stars, has been studied using CCD UBV photometry and spectroscopy. The file "mt91.dat" contains precise coordinates, UBV photometry, and spectral types from the study of Cygnus OB2, and merges the tables 2, 5 and 6 from the paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/855/68
- Title:
- Massive stars in the SDSS-IV/APOGEE SURVEY. I.
- Short Name:
- J/ApJ/855/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we make use of DR14 APOGEE spectroscopic data to study a sample of 92 known OB stars. We developed a near-infrared semi-empirical spectral classification method that was successfully used in case of four new exemplars, previously classified as later B-type stars. Our results agree well with those determined independently from ECHELLE optical spectra, being in line with the spectral types derived from the "canonical" MK blue optical system. This confirms that the APOGEE spectrograph can also be used as a powerful tool in surveys aiming to unveil and study a large number of moderately and highly obscured OB stars still hidden in the Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/11
- Title:
- Massive star variability in M31 from iPTF
- Short Name:
- J/ApJ/893/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using data from the (intermediate) Palomar Transient Factory (iPTF), we characterize the time variability of ~500 massive stars in M31. Our sample is those stars that are spectrally typed by Massey and collaborators, including Luminous Blue Variables, Wolf-Rayets, and warm and cool supergiants. We use the high-cadence, long-baseline (~5yr) data from the iPTF survey, coupled with data-processing tools that model complex features in the light curves. We find widespread photometric (R-band) variability in the upper Hertzsprung Russell diagram (or CMD) with an increasing prevalence of variability with later spectral types. Red stars (V-I>1.5) exhibit larger amplitude fluctuations than their bluer counterparts. We extract a characteristic variability timescale, t_ch_, via wavelet transformations that are sensitive to both continuous and localized fluctuations. Cool supergiants are characterized by longer timescales (>100 days) than the hotter stars. The latter have typical timescales of tens of days but cover a wider range, from our resolution limit of a few days to longer than 100 days. Using a 60 night block of data straddling two nights with a cadence of around 2 minutes, we extracted t_ch_ in the range 0.1-10 days with amplitudes of a few percent for 13 stars. Though there is broad agreement between the observed variability characteristics in the different parts of the upper CMD with theoretical predictions, detailed comparison requires models with a more comprehensive treatment of the various physical processes operating in these stars, such as pulsation, subsurface convection, and the effect of binary companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/874/66
- Title:
- MASSIVE survey. XII. Early-type galaxy gradients
- Short Name:
- J/ApJ/874/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the stellar populations as a function of the radius for 90 early-type galaxies (ETGs) in the MASSIVE survey, a volume-limited integral-field spectroscopic (IFS) galaxy survey targeting all northern-sky ETGs with an absolute K-band magnitude of M_K_{<}-25.3mag or a stellar mass of M_*_>~4x10^11^M_{sun}_, within 108Mpc. We are able to measure reliable stellar population parameters for individual galaxies out to 10-20kpc (1-3R_e_) depending on the galaxy. Focusing on ~R_e_ (~10kpc), we find significant correlations between the abundance ratios, {sigma}, and M^*^ at a large radius, but we also find that the abundance ratios saturate in the highest-mass bin. We see a strong correlation between the kurtosis of the line-of-sight velocity distribution (h4) and the stellar population parameters beyond R_e_. Galaxies with higher radial anisotropy appear to be older, with metal-poorer stars and enhanced [{alpha}/Fe]. We suggest that the higher radial anisotropy may derive from more accretion of small satellites. Finally, we see some evidence for correlations between environmental metrics (measured locally and on >5Mpc scales) and the stellar populations, as expected if satellites are quenched earlier in denser environments.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/357
- Title:
- 2MASS J18212815+1414010 field stars
- Short Name:
- J/MNRAS/455/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the OSIRIS camera at the 10.4m Gran Telescopio Canarias (GTC) to monitor the astrometric motion of the L4.5 dwarf 2M1821+14 over 17 months. The astrometric residuals of 11 epochs have an rms dispersion of 0.4mas, which is larger than the average precision of 0.23mas per epoch and hints towards an additional signal or excess noise. Comparison of the point-spread functions in OSIRIS and FORS2/VLT images reveals no differences critical for high-precision astrometry, despite the GTC's segmented primary mirror. We attribute the excess noise to an unknown effect that may be uncovered with additional data. For 2M1821+14, we measured a relative parallax of 10^6.15^+/-0.18mas and determined a correction of 0.50+/-0.05mas to absolute parallax, leading to a distance of 9.38+/-0.03pc. We excluded at 3{sigma} confidence the presence of a companion to 2M1821+14 down to a mass ratio of 0.1 (~5M_Jupiter_) with a period of 50-1000d and a separation of 0.1-0.7au. The accurate parallax allowed us to estimate the age and mass of 2M1821+14 of 120-700Myr and 0.049^+0.014^_-0.024_M_{sun}_, thus confirming its intermediate age and substellar mass. We complement our study with a parallax and proper motion catalogue of 587 stars (i'=~15.5-22) close to 2M1821+14, used as astrometric references. This study demonstrates submas astrometry with the GTC, a capability applicable for a variety of science cases including the search for extrasolar planets and relevant for future astrometric observations with E-ELT and TMT.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/179
- Title:
- 2MASS J15111324-2130030 metal-poor star abundances
- Short Name:
- J/ApJ/850/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapid neutron-capture or r-process is thought to produce the majority of the heavy elements (Z>30) in extremely metal-poor stars. The same process is also responsible for a significant fraction of the heavy elements in the Sun. This universality of the r-process is one of its characteristic features, as well as one of the most important clues to its astrophysical origin. We report the discovery of an extremely metal-poor field giant with [Sr,Ba/H]~-6.0 and [Sr,Ba/Fe]~-3.0, the lowest abundances of strontium and barium relative to iron ever observed. Despite its low abundances, the star 2MASS J151113.24-213003.0 has [Sr/Ba]=-0.11+/-0.14, therefore its neutron-capture abundances are consistent with the main solar r-process pattern that has [Sr/Ba]=-0.25. It has been suggested that extremely low neutron-capture abundances are a characteristic of dwarf galaxies, and we find that this star is on a highly eccentric orbit with an apocenter >~100kpc that lies in the disk of satellites in the halo of the Milky Way. We show that other extremely metal-poor stars with low [Sr,Ba/H] and [Sr,Ba/Fe] plus solar [Sr/Ba] tend to have orbits with large apocenters, consistent with a dwarf galaxy origin for this class of object. The nucleosynthesis event that produced the neutron-capture elements in 2MASS J151113.24-213003.0 must produce both strontium and barium together in the solar ratio. We exclude contributions from the s-process in intermediate-mass asymptotic giant branch or fast-rotating massive metal-poor stars, pair-instability supernovae, the weak r-process, and neutron-star mergers. We argue that the event was a Pop III or extreme Pop II core-collapse supernova explosion.
- ID:
- ivo://CDS.VizieR/J/A+A/584/A40
- Title:
- 2MASS J22560844+5954299 spectra
- Short Name:
- J/A+A/584/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SW Sex stars are assumed to represent a distinguished stage in CV evolution, making it especially important to study them. We discovered a new cataclysmic star and carried out prolonged and precise photometric observations, as well as medium- resolution spectral observations. Modelling these data allowed us to determine the physical parameters and to establish its peculiarities. To obtain a light curve solution we used model whose emission sources are a white dwarf surrounded by an accretion disk with a hot spot, a gaseous stream near the disk's lateral side, and a secondary star filling its Roche lobe. The obtained physical parameters are compared with those of other SW Sex-subtype stars.
- ID:
- ivo://CDS.VizieR/J/A+A/615/L12
- Title:
- 2MASS J04183483+2131275 spectrum
- Short Name:
- J/A+A/615/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the 10.4-m Gran Telescopio Canarias (GTC) with its low-dispersion optical spectrograph to obtain 10 spectra of 2277s each covering the range 6300-10300 Angstroms with a resolving power of R~500 for the Hyades brown dwarf 2MASSJ04183483+2131275. We detect lithium in absorption and Halpha in emission in this combined spectrum.
