We present a comprehensive analysis, including B and V light curves and 11 high-resolution spectra, to verify the orbital period and determine parameters. The spectroscopic and photometric analyses agree on a period of 0.896640+/-0.000007d. We determine a mass of 9.0+/-0.6M_{sun}_ for each component and temperatures of 28000+/-2000K. Both values are consistent with the spectral type B1V. The two stars are overfilling their respective Roche lobes, sharing a common envelope, and therefore the orbit is synchronised and circularised. Thetwo stars are in a very advanced stage of interaction, with their extreme physical similarity likely due to the common envelope. The expected evolution of such a system will very probably lead to a merger while still on the main sequence.
We are presenting here a study of the cold dust in the close environs of the ring nebula Gum 31. We aim at deriving the physical properties of the molecular gas and dust associated with the nebula, and investigating its correlation with the star formation in the region, that was probably triggered by the expansion of the ionization front against its environment. We make use of 870um emission data obtained with the Large APEX Bolometer Camera (LABOCA) to map the dust emission. The 870um emission provides an excellent probe of mass and density of dense molecular clouds. The obtained LABOCA image was compared to archival infrared, radio continuum, and optical images.
Gunn g, r, i photometry for the 7 clusters MRC0254-274, Cl0317+15, MS0418.3-3 844, Cl1141-283, A1689, A3594, S0781B is presented. For each cluster we derived the spatial distribution properties obtaining the core radius and the concentration parameters. Color properties of the cluster galaxy population are also briefly discussed.
We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2Gyr. We derive a radius (0.89+/-0.02R_Jup_) for the companion that is consistent with that predicted (0.914R_Jup_) by a model of a 1Gyr old, non-irradiated BD with a dusty atmosphere. The location of WASP-30b in the minimum of the mass-radius relation is consistent with the quantitative prediction of Chabrier & Baraffe, thus confirming the theory.
In this paper we introduce the deepest and most extensive ultraviolet extragalactic source catalogs of the Virgo Cluster area to date. Archival and targeted GALEX imaging is compiled and combined to provide the deepest possible coverage over ~120deg^2^ in the NUV (lambda_eff_=2316{AA}) and ~40deg^2^ in the FUV (lambda_eff_=1539{AA}) between 180{deg}<=RA<=195{deg} and 0{deg}<=DE<=20{deg}. We measure the integrated photometry of 1770 extended UV sources of all galaxy types and use GALEX pipeline photometry for 1,230,855 point-like sources in the foreground, within, and behind the cluster. Extended source magnitudes are reliable to m_UV_~22, showing a ~0.01{sigma} difference from their asymptotic magnitudes. Point-like source magnitudes have a 1{sigma} standard deviation within ~0.2mag down to m_uv_~23. The point-like source catalog is cross-matched with large optical databases and surveys including the SDSS DR9 (>1 million Virgo Cluster sources), the Next Generation Virgo Cluster Survey (NGVS; >13 million Virgo Cluster sources), and the NED (~30,000 sources in the Virgo Cluster). We find that 69% of the entire UV point-like source catalog has a unique optical counterpart, 11% of which are stars and 0.01% (129) are Virgo cluster members that are neither in the VCC nor part of the bright CGCG galaxy catalog (i.e., m_pg_<14.5). These data are collected in three catalogs containing the UV extended sources, the UV point-like sources, and the most relevant optical parameters of UV-optically matched point-like sources for further studies from SDSS. The GUViCS catalogs provide a unique set of data for future work on UV and multiwavelength studies in the cluster and background environments.
In this Letter, we analyze the radial ultraviolet-optical color distributions in a sample of low redshift green valley galaxies, with the Galaxy Evolution Explorer (GALEX)+Sloan Digital Sky Survey (SDSS) images, to investigate how the residual recent star formation is distributed in these galaxies. We find that the dust-corrected u-r colors of early-type galaxies (ETGs) are flat out to R_90_, while the colors monotonously turn blue when r>0.5 R_50_ for late-type galaxies (LTGs). More than half of the ETGs are blue-cored and have remarkable positive NUV-r color gradients, suggesting that their star formations are centrally concentrated. The rest have flat color distributions out to R_90_. The centrally concentrated star formation activity in a large portion of ETGs is confirmed by the SDSS spectroscopy, showing that ~50% of the ETGs have EW(H{alpha})>6.0 {AA}. Of the LTGs, 95% show uniform radial color profiles, which can be interpreted as a red bulge plus an extended blue disk. The links between the two kinds of ETGs, e.g., those objects having remarkable "blue-cores" and those having flat color gradients, are less known and require future investigations. It is suggested that the LTGs follow a general model by which quenching first occurs in the core regions, and then finally extend to the rest of the galaxy. Our results can be re-examined and have important implications for the IFU surveys, such as MaNGA and SAMI.
The Advanced LIGO and Virgo gravitational wave observatories detected a signal on 2019 August 14 during their third observing run, named GW190814. A large number of electromagnetic facilities conducted follow-up campaigns in the search for a possible counterpart to the gravitational wave event, which was made especially promising given the early source classification of a neutron star-black hole merger. We present the results of the GW follow-up campaign taken with the wide-field optical telescope MeerLICHT, located at the South African Astronomical Observatory Sutherland site. We use our results to constrain possible kilonova models. MeerLICHT observed more than 95% of the probability localisation each night for over a week in three optical bands (u,q,i) with our initial observations beginning almost 2 hours after the GW detection. We describe the search for new transients in MeerLICHT data and investigate how our limiting magnitudes can be used to constrain an AT2017gfo-like kilonova. A single new transient was found in our analysis of MeerLICHT data, which we exclude from being the electromagnetic counterpart to GW190814 owing to the existence of a spatially unresolved source at the coordinates of the transient in archival data. Using our limiting magnitudes, the confidence with which we can exclude the presence of an AT2017gfo-like kilonova at the distance of GW190814 was low (<10^-4^).
We present 12,155 new differential photometric observations in the V filter made with the Undergraduate Research Studies in Astronomy and NF\Observatory WebScopes, as well as 33 radial velocities from spectroscopic observations of the detached, 4.04 day double-lined eclipsing binary star GX Gem. Absolute dimensions of the components are determined from these new, and also from previously published, data with high precision (less than 0.7% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 1.488+/-0.011 solar masses and 2.327+/-0.012 solar radii for the primary, and 1.467+/-0.010 solar masses and 2.238+/-0.012 solar radii for the secondary. The effective temperatures and interstellar reddening of the stars are accurately determined from the spectra, uvby{beta}, and UBV photometry: 6195+/-100K for the primary, 6165+/-100K for the secondary, corresponding to spectral types of F7 and F7 V, and 0.068mag for the color excess E(b-y). Spectral line widths give rotational velocities that are synchronous with the mean orbital motion in a circular orbit.
It is not yet known if the properties of molecular gas in distant protocluster galaxies are significantly acted by their environment as galaxies are in local clusters. Through a deep, 64 hours of effective on-source integration with the Australian Telescope Compact Array (ATCA), we discovered a massive, M_mol_=2.0+/-0.2x0^11^M_{sun}_, extended, ~40kpc, CO(1-0)-emitting disk in the protocluster surrounding the radio galaxy, MRC1138-262. The galaxy, at z_CO_=2.1478, is a clumpy, massive disk galaxy, M*~5x10^11^M_{sun}_, which lies 250kpc in projection from MRC1138-262 and is a known H{alpha} emitter, named HAE229. This source has a molecular gas fraction of ~30%. The CO emission has a kinematic gradient along its major axis, centered on the highest surface brightness rest-frame optical emission, consistent with HAE229 being a rotating disk. Surprisingly, a significant fraction of the CO emission lies outside of the UV/optical emission. In spite of this, HAE229 follows the same relation between star-formation rate and molecular gas mass as normal field galaxies. HAE229 is the first CO(1-0) detection of an ordinary, star-forming galaxy in a protocluster.We compare a sample of cluster members at z>0.4 that are detected in low-order CO transitions, with a similar sample of sources drawn from the field.We confirm findings that the CO-luminosity and full-width at half maximum (FWHM) are correlated in starbursts and show that this relation is valid for normal high-z galaxies as well as for those in overdensities. We do not find a clear dichotomy in the integrated Schmidt-Kennicutt relation for protocluster and field galaxies. Our results suggest that environment does not have an impact on the "star-formation electronic efficiency" or the molecular gas content of high-redshift galaxies. Not finding any environmental dependence in these characteristics, especially for such an extended CO disk, suggests that environmentally-specific processes such as ram pressure stripping do not operate electronic efficiently in (proto)clusters.
