- ID:
- ivo://CDS.VizieR/J/ApJS/211/22
- Title:
- Updated photometry for star clusters in M33
- Short Name:
- J/ApJS/211/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The photometric characterization of M33 star clusters is far from complete. In this paper, we present homogeneous UBVRI photometry of 708 star clusters and cluster candidates in M33 based on archival images from the Local Group Galaxies Survey, which covers 0.8deg^2^ along the galaxy's major axis. Our photometry includes 387, 563, 616, 580, and 478 objects in the UBVRI bands, respectively, of which 276, 405, 430, 457, and 363 do not have previously published UBVRI photometry. Our photometry is consistent with previous measurements (where available) in all filters. We adopted Sloan Digital Sky Survey ugriz photometry for complementary purposes, as well as Two Micron All Sky Survey near-infrared JHK photometry where available. We fitted the spectral-energy distributions of 671 star clusters and candidates to derive their ages, metallicities, and masses based on the updated PARSEC simple stellar populations synthesis models. The results of our {chi}^2^ minimization routines show that only 205 of the 671 clusters (31%) are older than 2Gyr, which represents a much smaller fraction of the cluster population than that in M31 (56%), suggesting that M33 is dominated by young star clusters (<1Gyr).
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/745/56
- Title:
- Upper Sco members rotational velocities
- Short Name:
- J/ApJ/745/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present projected rotational velocities for 20 early-type (B8-A9) and 74 late-type (F2-M8) members of the ~5 Myr old Upper Scorpius OB Association derived from high-dispersion optical spectra obtained with the High Resolution Echelle Spectrometer on Keck I and the Magellan Inamori Kyocera Echelle on the Magellan Clay telescope. The spectroscopic sample is composed of stars and brown dwarfs with infrared signatures of circumstellar disks, both primordial and debris, and non-excess sources of comparable spectral type. We merge projected rotational velocities, accretion diagnostics, and Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer 24 {mu}m photometry to examine the relationship between rotation and circumstellar disks. The rotational velocities are strongly correlated with spectral type, a proxy for mass, such that the median vsin i for B8-A9-type stars is: 195+/-70km/s, F2-K4: 37.8+/-7.4km/s, K5-K9: 13.8^+21.3^_-8.2_km/s, M0-M5: 16.52+/-5.3km/s, and M5.5-M8: 17.72+/-8.1km/s. We find with a probability of >=0.99 that M-type stars and brown dwarfs having infrared excess suggestive of circumstellar disks rotate more slowly than their non-excess counterparts. A similar correlation is present among F2-K9-type stars, but only at the ~97% confidence level. Among the early-type (B8-A9) members, rotational velocities of the debris-disk and non-disk populations are indistinguishable. Considering the late-type (F2-M8) stars and brown dwarfs, we find a low fraction of slowly rotating, non-excess sources relative to younger star-forming regions, suggesting that most have spun up following disk dissipation. The few late-type (F2-M5) debris disk sources, which may be representative of stars that have recently dispersed their inner disks, are evenly divided between slow and moderate rotators.
- ID:
- ivo://CDS.VizieR/J/ApJ/651/L49
- Title:
- Upper Sco OB association IRAC observations
- Short Name:
- J/ApJ/651/L49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 4.5, 8 and 16um photometry from the Spitzer Space Telescope for 204 stars in the Upper Scorpius OB association. The data are used to investigate the frequency and properties of circumstellar disks around stars with masses between 0.1 and 20 at an age of 5Myr. We identify 35 stars that have emission at 8 or 16um in excess of the stellar photosphere.
2594. Upper Scorpius members
- ID:
- ivo://CDS.VizieR/J/other/NatAs/6.89
- Title:
- Upper Scorpius members
- Short Name:
- J/other/NatAs/6.
- Date:
- 03 Mar 2022 16:55:14
- Publisher:
- CDS
- Description:
- The nature and origin of free-floating planets (FFPs) are still largely unconstrained because of a lack of large homogeneous samples to enable a statistical analysis of their properties. So far, most FFPs have been discovered using indirect methods; microlensing surveys have proved particularly successful to detect these objects down to a few Earth masses. However, the ephemeral nature of microlensing events prevents any follow-up observations and individual characterization. Several studies have identified FFPs in young stellar clusters and the Galactic field but their samples are small or heterogeneous in age and origin. Here we report the discovery of between 70 and 170 FFPs (depending on the assumed age) in the region encompassing Upper Scorpius and Ophiuchus, the closest young OB association to the Sun. We found an excess of FFPs by a factor of up to seven compared with core-collapse model predictions, demonstrating that other formation mechanisms may be at work. We estimate that ejection from planetary systems might have a contribution comparable to that of core collapse in the formation of FFPs. Therefore, ejections due to dynamical instabilities in giant exoplanet systems must be frequent within the first 10Myr of a system's life.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/2474
- Title:
- USco ZYJHK1K2 photometry and proper motions
- Short Name:
- J/MNRAS/435/2474
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep ZYJ near-infrared survey of 13.5deg^2^ in the Upper Scorpius (USco) OB association. We photometrically selected ~100 cluster member candidates with masses in the range of 30-5 Jupiters, according to state-of-the-art evolutionary models. We identified 67 ZYJ candidates as bona fide members, based on complementary photometry and astrometry. We also extracted five candidates detected with Visible and Infrared Survey Telescope for Astronomy at YJ only. One is excluded using deep optical z-band imaging, while two are likely non-members, and three remain as potential members. We conclude that the USco mass function is more likely decreasing in the planetary-mass regime (although a flat mass function cannot yet be discarded), consistent with surveys in other regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/52
- Title:
- UV and IR observations for SINGS galaxies. I.
- Short Name:
- J/ApJ/757/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color (or ultraviolet spectral slope), i.e., the IRX-UV (or IRX-{beta}) relation, found in studies of starburst galaxies is a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation discovered for normal galaxies, however, complicates its usability. In order to investigate the cause of the dispersion and to have a better understanding of the nature of the IRX-UV relation, in this paper, we select five nearby spiral galaxies, and perform spatially resolved studies on each of the galaxies, with a combination of ultraviolet and infrared imaging data. We measure all positions within each galaxy and divide the extracted regions into young and evolved stellar populations. By means of this approach, we attempt to discover separate effects of dust attenuation and stellar population age on the IRX-UV relation for individual galaxies. In this work, in addition to dust attenuation, stellar population age is interpreted to be another parameter in the IRX-UV function, and the diversity of star formation histories is suggested to disperse the age effects. At the same time, strong evidence shows the need for more parameters in the interpretation of observational data, such as variations in attenuation/extinction law. Fractional contributions of different components to the integrated luminosities of the galaxies suggest that the integrated measurements of these galaxies, which comprise different populations, would weaken the effect of the age parameter on IRX-UV diagrams. The dependence of the IRX-UV relation on luminosity and radial distance in galaxies presents weak trends, which offers an implication of selective effects. The two-dimensional maps of the UV color and the infrared-to-ultraviolet ratio are displayed and show a disparity in the spatial distributions between the two galaxy parameters, which offers a spatial interpretation of the scatter in the IRX-UV relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/76
- Title:
- UV and IR properties for galaxies
- Short Name:
- J/ApJ/789/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-{beta} relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 {AA} bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 {AA} bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.
- ID:
- ivo://CDS.VizieR/J/AJ/126/1208
- Title:
- UVBI magnitudes and redshifts in HDF-South
- Short Name:
- J/AJ/126/1208
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 97 (*) spectroscopic redshifts of z<1 galaxies in the Hubble Deep Field South (HDF-S) and its flanking fields (FFs). In the HDF-S proper we observed approximately half the galaxies brighter than I_814_(AB)=24 and obtained redshifts for 76% of them. Targets in our HDF-S sample were preselected to be at z<1 based on photometric redshifts, while in the FFs a simple magnitude cut was used. The photometric redshift preselection in the HDF-S resulted in a spectroscopic success rate that is significantly higher than in the FFs, where no preselection was applied. The rms precision of our redshift measurements, determined from repeat observations, is {delta}z=0.0003. We present the photometry and redshifts for the 97 objects for which we secured spectroscopic redshifts and describe the basic properties of this sample. The photometry was derived from the HST observations; the spectroscopy was obtained at the VLT using the FORS2 spectrograph on the Kueyen (UT2) and Yepun (UT4) 8.2m telescopes. (*) Actually, 103 redshifts in table1.
- ID:
- ivo://CDS.VizieR/J/ApJS/235/16
- Title:
- UV emission of stars in LAMOST. I. Catalogs
- Short Name:
- J/ApJS/235/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the ultraviolet magnitudes for over three million stars in the LAMOST survey, in which 2,202,116 stars are detected by GALEX. For 889,235 undetected stars, we develop a method to estimate their upper limit magnitudes. The distribution of (FUV-NUV) shows that the color declines with increasing effective temperature for stars hotter than 7000K in our sample, while the trend disappears for the cooler stars due to upper atmosphere emission from the regions higher than their photospheres. For stars with valid stellar parameters, we calculate the UV excesses with synthetic model spectra, and find that the (FUV - NUV) versus R'_FUV_ can be fitted with a linear relation and late-type dwarfs tend to have high UV excesses. There are 87,178 and 1,498,103 stars detected more than once in the visit exposures of GALEX in the FUV and NUV, respectively. We make use of the quantified photometric errors to determine statistical properties of the UV variation, including intrinsic variability and the structure function on the timescale of days. The overall occurrence of possible false positives is below 1.3% in our sample. UV absolute magnitudes are calculated for stars with valid parallaxes, which could serve as a possible reference frame in the NUV. We conclude that the colors related to UV provide good criteria to distinguish between M giants and M dwarfs, and the variability of RR Lyrae stars in our sample is stronger than that of other A and F stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/406/420
- Title:
- UV/far-IR data of infrared excess sources
- Short Name:
- J/MNRAS/406/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the nature of Infrared Excess sources (IRX), which are proposed as candidates for luminous [LX(2-10keV)>10^43^erg/s] Compton thick (NH>2x10^24^cm^-2^) QSOs at z~~2. Lower redshift, z~~1, analogues of the distant IRX population are identified by first redshifting to z=2 the spectral energy distributions (SEDs) of all sources with secure spectroscopic redshifts in the AEGIS (6488) and the GOODS-North (1784) surveys and then selecting those that qualify as IRX sources at that redshift. A total of 19 galaxies are selected. The mean redshift of the sample is z~~1. We do not find strong evidence for Compton thick QSOs in the sample. For nine sources with X-ray counterparts, the X-ray spectra are consistent with Compton thin active galactic nucleus (AGN). Only three of them show tentative evidence for Compton thick obscuration. The SEDs of the X-ray undetected population are consistent with starburst activity.
