We have extended and refined the existing young stellar object (YSO) catalogs for the Orion A molecular cloud, the closest massive star-forming region to Earth. This updated catalog is driven by the large spatial coverage (18.3deg^2^, ~950pc^2^), seeing limited resolution (~0.7''), and sensitivity (K_s_<19mag) of the ESO-VISTA near-infrared survey of the Orion A cloud (VISION). Combined with archival mid- to far-infrared data, the VISTA data allow for a refined and more robust source selection. We estimate that among previously known protostars and pre-main-sequence stars with disks, source contamination levels (false positives) are at least ~6.4% and ~2.3%, respectively, mostly due to background galaxies and nebulosities. We identify 274 new YSO candidates using VISTA/Spitzer based selections within previously analyzed regions, and VISTA/WISE based selections to add sources in the surroundings, beyond previously analyzed regions. The WISE selection method recovers about 59% of the known YSOs in Orion A's low-mass star-forming part L1641, which shows what can be achieved by the all-sky WISE survey in combination with deep near-infrared data in regions without the influence of massive stars. The new catalog contains 2980 YSOs, which were classified based on the de-reddened mid-infrared spectral index into 188 protostars, 185 flat-spectrum sources, and 2607 pre-main-sequence stars with circumstellar disks. We find a statistically significant difference in the spatial distribution of the three evolutionary classes with respect to regions of high dust column-density, confirming that flat-spectrum sources are at a younger evolutionary phase compared to Class IIs, and are not a sub-sample seen at particular viewing angles.
The validity of the unified active galactic nuclei (AGN) model has been challenged in the last decade, especially when different types of AGNs are considered to only differ in the viewing angle to the torus. We aim to assess the importance of the viewing angle in classifying different types of Seyfert galaxies in spectral energy distribution (SED) modelling. We retrieve photometric data from publicly available astronomical databases: CDS and NED, to model SEDs with X-CIGALE in a sample of 13173 Seyfert galaxies located at redshift range from z=0 to z=3.5, with a median redshift of z=~0.2. We assess whether the estimated viewing angle from the SED models reflects different Seyfert classifications. Two AGN models with either a smooth or clumpy torus structure are adopted in this paper. We find that the viewing angle in Type-1 AGNs is better constrained than in Type-2 AGNs. Limiting the viewing angles representing these two types of AGNs do not affect the physical parameter estimates such as star-formation rate (SFR) or AGN fractional contribution (fAGN). In addition, the viewing angle is not the most discriminating physical parameter to differentiate Seyfert types. We suggest that the observed and intrinsic AGN disc luminosity can: i) be used in z<0.5 studies to distinguish between Type-1 and Type-2 AGNs, and ii) explain the probable evolutionary path between these AGN types. Finally, we propose the use of X-CIGALE for AGN galaxy classification tasks. All data from the 13173 SED fits are available at Zenodo.
We present deep V and I photometry of the isolated dwarf galaxy VV124=UGC4879, obtained from archival images taken with the Hubble Space Telescope - Advanced Camera for Surveys. In the color-magnitude diagrams of stars at distances larger than 40" from the center of the galaxy, we clearly identify for the first time a well-populated old Horizontal Branch (HB). We show that the distribution of these stars is more extended than that of Red Clump stars. This implies that very old and metal poor populations becomes more and more dominant in the outskirts of VV124. We also identify a massive (M=1.2+/-0.2x10^4^M_{sun}_) young (age=250+/-50Myr) star cluster (C1), as well as another of younger age (C2<~30+/-10Myr) with a mass similar to classical open clusters (M<=3.3+/-0.5x10^3^M_{sun}_). Both clusters lie at projected distances smaller than 100pc from the center of the galaxy.
New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized with radiative lifetime measurements to determine the new transition probabilities. Generally good agreement is found between this work and previously reported V II transition probabilities. Two spectrometers, independent radiometric calibration methods, and independent data analysis routines enable a reduction in systematic uncertainties, in particular those due to optical depth errors. In addition, new hyperfine structure constants are measured for selected levels by least squares fitting line profiles in the FTS spectra. The new V II data are applied to high resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to determine new, more accurate V abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. Very good agreement is found between our new solar photospheric V abundance, log{epsilon}(V)=3.95 from 15 V II lines, and the solar-system meteoritic value. In HD 84937, we derive [V/H]=-2.08 from 68 lines, leading to a value of [V/Fe]=0.24.
We present the optical/infrared (O/IR) light curve of the black hole X-ray binary GX 339-4 collected at the SMARTS 1.3m telescope from 2002 to 2010. During this time the source has undergone numerous state transitions including hard-to-soft state transitions when we see large changes in the near-IR flux accompanied by modest changes in optical flux, and three rebrightening events in 2003, 2005, and 2007 after GX 339-4 transitioned from the soft state to the hard. All but one outburst show similar behavior in the X-ray hardness-intensity diagram. We show that the O/IR colors follow two distinct tracks that reflect either the hard or soft X-ray state of the source. Thus, either of these two X-ray states can be inferred from O/IR observations alone. From these correlations we have constructed spectral energy distributions of the soft and hard states. During the hard state, the near-IR data have the same spectral slope as simultaneous radio data when GX 339-4 was in a bright optical state, implying that the near-IR is dominated by a non-thermal source, most likely originating from jets. Non-thermal emission dominates the near-IR bands during the hard state at all but the faintest optical states, and the fraction of non-thermal emission increases with increasing optical brightness. The spectral slope of the optical bands indicate that a heated thermal source is present during both the soft and hard X-ray states, even when GX 339-4 is at its faintest optical state. We have conducted a timing analysis of the light curve for the hard and soft states and find no evidence of a characteristic timescale within the range of 4-230days.
Whiting 1 is a member of the fast-growing group of young globular clusters in the Milky Way halo. Preliminary estimates of its fundamental parameters have been provided using optical photometry and low-resolution spectroscopy. In an attempt to strengthen our knowledge of Whiting 1, in this study we employ a complementary approach. Isochrone fitting method was applied on the near-infrared colour-magnitude diagram and yields an age t=5.7+/-0.3Gyr, metallicity z=0.006+/-0.001 ([Fe/H]=-0.5+/-0.1) and distance modulus (m-M)0=17.48+/-0.10. Our results confirm that Whiting 1 is a young and moderately metal-rich globular cluster. It is one of the youngest from the Sgr dSph. We fitted an Elson, Fall and Freeman (EFF) profile to the near-infrared number counts, and measured cluster core radius r_c_=9.1+/-3.9". Two probable eclipsing variables in the cluster were found from multi-epoch V-band photometry. Finally, an unknown galaxy cluster was identified on our K versus (J-K) colour-magnitude diagram. It has a redshift z~1, and it is located at about 1arcmin from the centre of Whiting 1 at {alpha}_J2000_= 02:02:56.6, {delta}_J2000_=-03:16:09, contaminating the cluster photometry.
We study the red giant populations of two dwarf elliptical (dE) galaxies, AM 1339-445 and AM 1343-452. The galaxies are members of the Centaurus A group (D~3.8Mpc), and are classified as outlying (R~350kpc) satellites of Cen A. The analysis is based on near-IR photometry for individual red giant stars, derived from images obtained with ISAAC on the VLT, and on optical V and I photometry, derived from WFPC2 images retrieved from the HST science archive. The data enable us to investigate the stellar populations of these galaxies in the vicinity of the red giant branch (RGB) tip. In both systems we find stars above the RGB tip, which we interpret as intermediate-age upper-AGB stars. Their luminosities suggest ages of approximately 6.5+/-1 and 4+/-1Gyr as estimates for the epoch of the last episode of significant star formation in these systems. In both cases the number of upper-AGB stars suggests that ~15% of the total stellar population is in the form of intermediate-age stars.
The VIKING survey with VISTA (ESO programme ID 179.A-2004) is a wide area (eventually 1500 sq.degrees), intermediate-depth (5-sigma detection limit J=21 on Vega system) near-infrared imaging survey, in the five broadband filters Z, Y, J, H, Ks. The planned sky coverage is at high galactic latitudes, and includes two main stripes 70x10{deg}^2^ each: one in the South Galactic cap near Dec~-30{deg}, and one near Dec~0{deg} in the North galactic cap; in addition, there are two smaller outrigger patches called GAMA09 and CFHLS-W1. Science goals include z>6.5 quasars, extreme brown dwarfs, and multiwavelength coverage and identifications for a range of other imaging surveys, notably VST-KIDS and Herschel-ATLAS. This first public data release of data taken between the 12th of November 2009 and the 13th of February 2011 includes 151 tiles with complete coverage in all five VIKING filters (55 in GAMA09/12/14, 91 in SGP and 5 in CFHLS-W1) i.e. 226 square degrees, and includes approximately 14,773,385 total sources (including low-reliability single-band detections) and the imaging and source lists total 314.4GB. The coverage in each of the five sub-areas is not completely contiguous but any inter-tile gaps are relatively small. More details can be found in the accompanying documentation: viking_cat_dr1.pdf
The VIKING survey with VISTA (ESO programme ID 179.A-2004) is a wide area (eventually 1500 sq.degrees), intermediate-depth (5-sigma detection limit J=21 on Vega system) near-infrared imaging survey, in the five broadband filters Z, Y, J, H, Ks. The planned sky coverage is at high galactic latitudes, and includes two main stripes 70x10{deg}^2^ each: one in the South Galactic cap near Dec~-30{deg}, and one near Dec~0{deg} in the North galactic cap; in addition, there are two smaller outrigger patches called GAMA09 and CFHLS-W1. Science goals include z>6.5 quasars, extreme brown dwarfs, and multiwavelength coverage and identifications for a range of other imaging surveys, notably VST-KIDS and Herschel-ATLAS. This second public data release of VIKING data covers all of the highest quality data taken between the start of the survey (12th of November 2009) and the end of Period 92 (30th September 2013). This release supersedes the first release (VIKING and VIKING CAT published 28.06.2013 and 16.12.2013 respectively) as it includes improved CASU processing (V1.3) that gives better tile grouting and zero point corrections This release contains 396 tiles with coverage in all five VIKING filters, 379 of which have a deep co-add in J, and an additional 81 with at least two filters where the second OB has not been executed yet or one filter in an OB was poor quality. These 477 fields cover a total of ~690 square degrees and the resulting catalogues include a total of 46,270,162 sources (including low-reliability single-band detections). The imaging and catalogues (both single-band and band-merged) total 839.3GB. The coverage in each of the five sub-areas is not completely contiguous but any inter-tile gaps are relatively small. More details can be found in the accompanying documentation: viking_cat_dr2.pdf
We analyze photometry and spectroscopy of a sample of 63 clusters at 0.3<=z<=0.9 drawn from the Las Campanas Distant Cluster Survey to empirically constrain models of cluster galaxy evolution. Our data originate from a variety of telescopes and instruments. The candidate galaxy clusters are identified using drift-scan images and techniques described briefly below for context but in full detail by Gonzalez et al. (2001, Cat. <J/ApJS/137/117>).
