We present spectroscopic observations of 466 galaxies in and around a superstructure at z~0.84 targeted by the VIMOS Spectroscopic Survey of a Supercluster in the COSMOS eld (VIS3COS). We use [OII]3727, H{delta}, and Dn4000 to trace recent, medium-, and long-term star formation histories and investigate the eect of stellar mass and local environment on them. By studying trends in individual and composite galaxy spectra, we find that stellar mass and environment play a role in the observed galactic properties. Galaxies with low stellar mass (10<log10(M*/M_{sun}_)<10.5) in the eld show the strongest H{delta} absorption. Similarly, the massive population (log10(M*/M_{sun}_) > 11) shows an increase in H absorption strengths in intermediate-density environments (e.g. filaments). Galaxies with intermediate stellar mass (10.5<log10(M*/M_{sun}_)<11) have similar H{delta} absorption proles in all environments, but show an indication of enhanced [OII] emission in intermediate-density environments. This indicates that field galaxies with low stellar mass and lament galaxies with high stellar mass are more likely to have experienced a recent burst of star formation, while galaxies of the intermediate stellar-mass show an increase of star formation at lament-like densities. We also find that the median [OII] equivalent width (|EW[OII]|) decreases from 27+/-2{AA} to 2.0^+0,5^_-0.4_{AA} and Dn4000 increases from 1.09+/-0.01 to 1.56+/-0.03 with increasing stellar mass (from ~10^9.25^ to ~10^11.35^M_{sun}_). For the dependence on the environment, we find that at fixed stellar mass, |EW[OII]| is tentatively lower in environments with higher density. We find for Dn4000 that the increase with stellar mass is sharper in denser environments, which indicates that these environments may accelerate galaxy evolution. Moreover, we find higher Dn4000 values in denser environments at fixed stellar mass, suggesting that galaxies are on average older and/or more metal rich in these dense environments. This set of tracers depicts a scenario where the most massive galaxies have, on average, the lowest specic star formation rates and the oldest stellar populations (age>~1Gyr, showing a mass-downsizing eect). We also hypothesize that the observed increase in star formation (higher EW[OII], higher specic star formation rate) at intermediate densities may lead to quenching because we find that the quenched fraction increases sharply from the lament to cluster-like regions at similar stellar masses.
Using visible, radio, microwave, and submillimeter data, we study several lines of sight toward stars generally closer than 1kpc on a component-by-component basis. We derive the component structure seen in absorption at visible wavelengths from CaII, CaI, KI, CH, CH+, and CN and compare it to emission from HI, CO and its isotopologues, and C+ from the GOT C+ (Galactic Observations of Terahertz C+) survey (Langer+ 2010A&A...521L..17L). The correspondence between components in emission and absorption helps create a more unified picture of diffuse atomic and molecular gas in the interstellar medium. We also discuss how these tracers are related to the CO-dark H2 gas probed by C+ emission and discuss the kinematic connections among the species observed.
We have investigated the shape of the extinction curve in the infrared up to ~25{mu}m for the Orion A star-forming complex. The basis of this work is near-infrared data acquired with the Visual and Infrared Survey Telescope for Astronomy, in combination with Pan-STARRS and mid-infrared Spitzer photometry. We obtain colour excess ratios for eight passbands by fitting a series of colour-colour diagrams. The fits are performed using Markov chain Monte Carlo methods, together with a linear model under a Bayesian formalism. The resulting colour excess ratios are directly interpreted as a measure of the extinction law. We show that the Orion A molecular cloud is characterized by flat mid-infrared extinction, similar to many other recently studied sightlines. Moreover, we find statistically significant evidence that the extinction law from ~1{mu}m to at least ~6{mu}m varies across the cloud. In particular, we find a gradient along galactic longitude, where regions near the Orion Nebula Cluster show a different extinction law compared to L1641 and L1647, the low-mass star-forming sites in the cloud complex. These variations are of the order of only 3% and are most likely caused by the influence of the massive stars on their surrounding medium. While the observed general trends in our measurements are in agreement with model predictions, both well-established and new dust grain models are not able to fully reproduce our infrared extinction curve. We also present a new extinction map featuring a resolution of 1' and revisit the correlation between extinction and dust optical depth. This analysis shows that cloud substructure, which is not sampled by background sources, affects the conversion factor between these two measures. In conclusion, we argue that specific characteristics of the infrared extinction law are still not well understood, but Orion A can serve as an unbiased template for future studies.
Orion A hosts the nearest massive star factory, thus offering a unique opportunity to resolve the processes connected with the formation of both low- and high-mass stars. Here we present the most detailed and sensitive near-infrared (NIR) observations of the entire molecular cloud to date. With the unique combination of high image quality, survey coverage, and sensitivity, our NIR survey of Orion A aims at establishing a solid empirical foundation for further studies of this important cloud. In this first paper we present the observations, data reduction, and source catalog generation. To demonstrate the data quality, we present a first application of our catalog to estimate the number of stars currently forming inside Orion A and to verify the existence of a more evolved young foreground population. We used the European Southern Observatory's (ESO) Visible and Infrared Survey Telescope for Astronomy (VISTA) to survey the entire Orion A molecular cloud in the NIR J, H, and K_S_ bands, covering a total of ~18.3deg^2^. We implemented all data reduction recipes independently of the ESO pipeline. Estimates of the young populations toward Orion A are derived via the K_S_-band luminosity function. Our catalog (799995 sources) increases the source counts compared to the Two Micron All Sky Survey by about an order of magnitude. The 90% completeness limits are 20.4, 19.9, and 19.0mag in J, H, and K_S_, respectively. The reduced images have 20% better resolution on average compared to pipeline products. We find between 2300 and 3000 embedded objects in Orion A and confirm that there is an extended foreground population above the Galactic field, in agreement with previous work. The Orion A VISTA catalog represents the most detailed NIR view of the nearest massive star-forming region and provides a fundamental basis for future studies of star formation processes toward Orion.
Half of the Seyfert-2 galaxies escaped detection of broad lines in their polarised spectra observed so far. Some authors have suspected that these non-HBLRs contain real Sy2 nuclei without intrinsic broad line region hidden behind a dust torus. If this were true, then their nuclear structure would fundamentally differ from that of Sy2s with polarised broad lines: in particular, they would not be explained by orientation-based AGN unification. Further arguments for two physically different Sy2 populations have been derived from the warm and cool IRAS F25/F60 ratios. These ratios, however, refer to the entire host galaxies and are unsuitable to conclusively establish the absence of a nuclear dust torus. Instead, a study of the Seyfert-2 dichotomy should be performed on the basis of nuclear properties only. Here we present the first comparison between [OIII] {lambda} 5007{AA} and mid-infrared imaging at matching spatial resolution. The aim is to check whether the nuclear dust emission scales with AGN luminosity as traced by [OIII].
We aim at identifying very low-mass isolated planetary-mass member candidates in the nearest OB association to the Sun, Upper Scorpius (145pc; 5-10Myr), to constrain the form and shape of the luminosity function and mass spectrum in this regime. We conducted a deep multi-band (Y=21.2, J=20.5, Z=22.0mag) photometric survey of six square degrees in the central region of Upper Scorpius. We extend the current sequence of astrometric and spectroscopic members by about two magnitudes in Y and one magnitude in J, reaching potentially T-type free-floating members in the association with predicted masses below 5 Jupiter masses, well into the planetary-mass regime. We extracted a sample of 57 candidates in this area and present infrared spectroscopy confirming two of them as young L-type members with characteristic spectral features of 10Myr-old brown dwarfs. Among the 57 candidates, we highlight 10 new candidates fainter than the coolest members previously confirmed spectroscopically. We do not see any obvious sign of decrease in the mass spectrum of the association, suggesting that star processes can form substellar objects with masses down to 4-5 Jupiter masses.
VIDEO is a ~12 square degrees survey in the near-infrared Z, Y, J, H and Ks bands,over the ELAIS-S1, XMMLS, and ECDFS extragalactic fields. This document describes the catalog released for the deep stracked data in the VIDEO-XMM3 field, which also covers the Canada-France-Hawaii Telescope Legacy Survey Deep-1 field (CFHTLS-D1).
All MAST catalog holdings are available via Cone Search endpoints.
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We report on our analysis of the VISTA Orion ZY JHK_s_ photometric data (completeness magnitudes of Z=22.6 and J=21.0 mag) focusing on a circular area of 2798.4arcmin^2^ around the young {sigma} Orionis star cluster (~3Myr, ~352pc, and solar metallicity). The combination of the VISTA photometry with optical, WISE and Spitzer data allows us to identify a total of 210 {sigma} Orionis member candidates with masses in the interval 0.25-0.004M_{sun}_, 23 of which are new planetary-mass object findings. These discoveries double the number of cluster planetary-mass candidates known so far. One object has colors compatible with a T spectral type. The {sigma} Orionis cluster harbors about as many brown dwarfs (69, 0.072-0.012M_{sun}_) and planetary-mass objects (37, 0.012-0.004M_{sun}_) as very low mass stars (104, 0.25-0.072M_{sun}_). Based on Spitzer data, we derive a disk frequency of ~40% for very low mass stars, brown dwarfs, and planetary-mass objects in {sigma} Orionis. The radial density distributions of these three mass intervals are alike: all are spatially concentrated within an effective radius of 12' (1.2pc) around the multiple star {sigma} Ori, and no obvious segregation between disk-bearing and diskless objects is observed.
The VISTA Magellanic Cloud (VMC; PI: M.-R. L. Cioni) survey is collecting deep K_s_-band time series photometry of the pulsating variable stars hosted by the system formed by the two Magellanic Clouds (MCs) and the bridge connecting them. In this paper, we present the first results for classical Cepheids, from the VMC observations of two fields in the Large Magellanic Cloud (LMC), centred on the South Ecliptic Pole and the 30 Doradus star-forming regions, respectively. The VMC K_s_-band light curves of the Cepheids are well sampled (12 epochs) and of excellent precision (typical errors of ~0.01mag). We were able to measure for the first time the K_s_magnitude of the faintest classical Cepheids in the LMC (K_s_~17.5mag), which are mostly pulsating in the first overtone (FO) mode, and to obtain FO period--luminosity (PL), period-Wesenheit (PW) and period-luminosity-colour (PLC) relations, spanning the full period range from 0.25 to 6d. Since the longest period Cepheid in our data set has a variability period of 23d, we have complemented our sample with literature data for brighter F Cepheids. On this basis, we have built a PL relation in the K_s_ band that, for the first time, includes short-period - hence low-luminosity - pulsators, and spans the full range from 1.6 to 100 d in period.We also provide the first ever empirical PW and PLC relations using the (V-K_s_) colour and time series K_s_photometry. The very small dispersion (~0.07mag) of these relations makes them very well suited to study the three-dimensional geometry of the Magellanic system. The use of 'direct' (parallax- and Baade--Wesselink-based) distance measurements to both Galactic and LMC Cepheids allowed us to calibrate the zero-points of the PL, PW and PLC relations obtained in this paper, and in turn to estimate an absolute distance modulus of (m-M)_0_=18.46+/-0.03mag for the LMC. This result is in agreement with most of the latest literature determinations based on classical Cepheids.
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