A sample of G and K giants approximately 4kpc from the Sun, covering the abundance range from solar to extreme halo has been selected without kinematic bias in a field aligned to measure galactic rotation. Accurate abundances, distances, and radial velocities have been measured. This sample has been combined with nonkinematically selected solar neighborhood objects taken from the literature, in order to examine the kinematics of the transition from disk to "thick disk" to halo. The metal-rich objects in the sample, with 0>[Fe/H]>-0.8, rotate rapidly around the galactic center and have low azimuthal velocity dispersion, {sigma}_{phi}_=40+/-10km/s. For objects in the range -0.5>[Fe/H]>-0.8, we find a small value for the asymmetric drift of 35+/-10km/s. We associate these objects with the thick disk, confirming the kinematical results of Ratnatunga and Freeman (1989, Cat.<V/65>) and others. In the abundance range -1.0>[Fe/H]>=-1.6 we find, in addition to objects with normal halo kinematics, objects in a disk configuration, confirming the results of Norris, Bessell, and Pickles (1985ApJS...58..463N). This disk is rotating rapidly, V_rot_=170+/-15km/s, and has a scale height of 1.4+/-0.7kpc, these kinematical and spatial properties are similar to those of the thick disk. We show that these objects have different kinematics from that of the globular clusters and a sample of local RR Lyraes in the same abundance range. This suggests to us that these objects are better associated with the thick disk than the halo, and we refer to them as "metal-weak thick-disk stars". Hence we suggest that the conventional chemical description of the thick disk (Gilmore and Wyse, 1985AJ.....90.2015G) be widened to include stars with abundances as low as [Fe/H]=-1.6. At the galactic plane, the density of these metal-weak thick-disk stars is similar to that of halo stars, so they significantly affect the measurement, from samples selected on abundance, of the components of the velocity ellipsoid for the halo in the solar neighborhood. For the halo giants in our sample we measure {sigma}_{phi}_=102+/-24 and V_rot_=17+/-24km/s. The rotation velocity and velocity ellipsoid for the metal-weak halo in the solar neighborhood have been rederived for objects with [Fe/H]<=-1.6 from the large sample of Norris (1986ApJS...61..667N), thus removing the possibility of contamination by metal-weak thick-disk stars. We derive V_rot_=25+/-15km/s and ({sigma}_r_, {sigma}_{phi}_, {sigma}_{theta}_)=(133+/-8, 98+/-13, 94+/-6)km/s. These values are more consistent with other information about the shape of the halo. For a description of the DDO photometric system, see e.g. <GCPD/12>
As tracers of star formation, galaxy assembly and mass distribution, globular clusters have provided important clues to our understanding of early-type galaxies. But their study has been mostly constrained to galaxy groups and clusters where early-type galaxies dominate, leaving the properties of the globular cluster systems (GCSs) of isolated ellipticals as a mostly uncharted territory. We present Gemini-South/GMOS g'i' observations of five isolated elliptical galaxies: NGC 3962, NGC 2865, IC 4889, NGC 2271 and NGC 4240. Photometry of their GCSs reveals clear color bimodality in three of them, remaining inconclusive for the other two. All the studied GCSs are rather poor with a mean specific frequency S_N_~1.5, independently of the parent galaxy luminosity. Considering also previous work, it is clear that bimodality and especially the presence of a significant, even dominant, population of blue clusters occurs at even the most isolated systems, casting doubts on a possible accreted origin of metal-poor clusters as suggested by some models. Additionally, we discuss the possible existence of ultra-compact dwarfs around the isolated elliptical NGC 3962.
We present deep stellar photometry of the Bootes I dwarf spheroidal galaxy in g- and i-band filters, taken with the Dark Energy Camera at Cerro Tololo in Chile. Our analysis reveals a large, extended region of stellar substructure surrounding the dwarf, as well as a distinct overdensity encroaching on its tidal radius. A radial profile of the Bootes I stellar distribution shows a break radius indicating the presence of extra-tidal stars. These observations strongly suggest that Bootes I is experiencing tidal disruption, although not as extreme as that exhibited by the Hercules dwarf spheroidal. Combined with revised velocity dispersion measurements from the literature, we see evidence suggesting the need to review previous theoretical models of the Bootes I dwarf spheroidal galaxy.
We present Gemini South GMOS g, i photometry of 14 intermediate-age Large Magellanic Cloud (LMC) star clusters, namely: NGC 2155, 2161, 2162, 2173, 2203, 2209, 2213, 2231, 2249, Hodge 6, SL 244, 505, 674, and 769, as part of a continuing project to investigate the extended main-sequence turn-off (EMSTO) phenomenon. Extensive artificial star tests were made over the observed field of view. These tests reveal the observed behaviour of photometric errors with magnitude and crowding. The cluster stellar density radial profiles were traced from star counts over the extent of the observed field. We adopt cluster radii and build colour-magnitude diagrams (CMDs) with cluster features clearly identified. We used the cluster (g, g-i) CMDs to estimate ages from the matching of theoretical isochrones. The studied LMC clusters are confirmed to be intermediate-age clusters, which range in age 9.10<log(t)<9.60. NGC 2162 and NGC 2249 look like new EMSTO candidates, in addition to NGC 2209, on the basis of having dual red clumps.
We present wide-field g- and i-band stellar photometry of the Sextans dwarf spheroidal galaxy and its surrounding area out to four times its half-light radius (r_h_=695pc), based on images obtained with the Dark Energy Camera at the 4-m Blanco telescope at CTIO. We find clear evidence of stellar substructure associated with the galaxy, extending to a distance of 82-arcmin (2kpc) from its centre. We perform a statistical analysis of the overdensities and find three distinct features, as well as an extended halo-like structure, to be significant at the 99.7 per cent confidence level or higher. Unlike the extremely elongated and extended substructures surrounding the Hercules dwarf spheroidal galaxy, the overdensities seen around Sextans are distributed evenly about its centre, and do not appear to form noticeable tidal tails. Fitting a King model to the radial distribution of Sextans stars yields a tidal radius r_t_=83.2-arcmin+/-7.1 arcmin (2.08+/-0.18kpc), which implies the majority of detected substructure is gravitationally bound to the galaxy. This finding suggests that Sextans is not undergoing significant tidal disruption from the Milky Way, supporting the scenario in which the orbit of Sextans has a low eccentricity.
The benchmark exoplanet GJ 1214b is one of the best studied transiting planets in the transition zone between rocky Earth-sized planets and gas or ice giants. This class of super-Earth or mini-Neptune planets is unknown in our solar system, yet is one of the most frequently detected classes of exoplanets. Understanding the transition from rocky to gaseous planets is a crucial step in the exploration of extrasolar planetary systems, in particular with regard to the potential habitability of this class of planets. GJ 1214b has already been studied in detail from various platforms at many different wavelengths. Our airborne observations with the Stratospheric Observatory for Infrared Astronomy (SOFIA) add information in the Paschen-{alpha}cont. 1.9um infrared wavelength band, which is not accessible by any other current ground- or space-based instrument due to telluric absorption or limited spectral coverage. We used FLIPO, the combination of the High-speed Imaging Photometer for Occultations (HIPO) and the First Light Infrared TEst CAMera (FLITECAM) and the Focal Plane Imager (FPI+) on SOFIA to comprehensively analyse the transmission signal of the possible water-world GJ 1214b through photometric observations during transit in three optical and one infrared channels. We present four simultaneous light curves and corresponding transit depths in three optical and one infrared channel, which we compare to previous observations and current synthetic atmospheric models of GJ 1214b. The final precision in transit depth is between 1.5 and 2.5 times the theoretical photon noise limit, not sensitive enough to constrain the theoretical models any better than previous observations. This is the first exoplanet observation with SOFIA that uses its full set of instruments available to exoplanet spectrophotometry. Therefore we use these results to evaluate SOFIAs potential in this field and suggest future improvements.
We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-velocity (RV) time series from the HARPS-N spectrograph, consisting in 151 HARPS-N measurements taken over 3.5yr. GJ 625 b is a planet with a minimum mass Msini of 2.82+/-0.51 M_Earth_ with an orbital period of 14.628+/-0.013 days at a distance of 0.078AU of its parent star. The host star is the quiet M2 V star GJ 625, located at 6.5pc from the Sun. We find the presence of a second radial velocity signal in the range 74-85 days that we relate to stellar rotation after analysing the time series of CaII H&K and H{alpha} spectroscopic indicators, the variations of the FWHM of the CCF and and the APT2 photometric light curves. We find no evidence linking the short period radial velocity signal to any activity proxy.
We are introducing a value-added full-sky galaxy catalog with high completeness for identifying gravitational wave (GW) sources in order to support future electromagnetic (EM) follow-up projects of the LIGO/Virgo Collaboration. The catalog GLADE (Galaxy List for the Advanced Detector Era) has been constructed (combined and matched) from four existing galaxy catalogs: GWGC, 2MPZ, 2MASS XSC and HyperLEDA. It contains 1918147 galaxies, which is two orders of magnitude greater than the number of galaxies in the GWGC catalog alone (53312), which is currently in use by the collaboration. Furthermore we considered it as a crucial requirement towards the catalog to contain B-band magnitudes and distances for all entries. Therefore we have associated these properties for 548876 2MASS galaxies which lacked them with a regression algorithm teached on a subsample of the 2MPZ catalog. Our catalog is complete to 73Mpc and even at 300Mpc has a relatively high completeness (53%). Naturally, our catalog could be used in a broad range of various astrophysical projects besides EM follow-up efforts.We are introducing a value-added full-sky galaxy catalog with high completeness for identifying gravitational wave (GW) sources in order to support future electromagnetic (EM) follow-up projects of the LIGO/Virgo Collaboration. The catalog has been constructed (combined and matched) from four existing galaxy catalogs: GWGC, 2MPZ, 2MASS XSC and HyperLEDA. It contains 1918147 galaxies, which is two orders of magnitude greater than the number of galaxies in the GWGC catalog alone (53312), which is currently in use by the collaboration. Furthermore we considered it as a crucial requirement towards the catalog to contain B-band magnitudes and distances for all entries. Therefore we have associated these properties for 548,876 2MASS galaxies which lacked them with a regression algorithm teached on a subsample of the 2MPZ catalog. Our catalog is complete to 73 Mpc and even at 300 Mpc has a relatively high completeness (53%). Naturally, our catalog could be used in a broad range of various astrophysical projects besides EM follow-up efforts. For a brief overview of the GLADE project, check out the talk slides (http://aquarius.elte.hu/glade/GLADE_GDalya_LVC2015September.pdf) presented at the 2015 September LIGO-Virgo Collaboration Meeting in Budapest, Hungary. If you have any questions or suggestions about the catalog, please send us an email: dalyag@caesar.elte.hu
We introduce a value-added full-sky catalogue of galaxies, named as Galaxy List for the Advanced Detector Era, or GLADE. The purpose of this catalogue is to (i) help identifications of host candidates for gravitational-wave events, (ii) support target selections for electromagnetic follow-up observations of gravitational-wave candidates, (iii) provide input data on the matter distribution of the local Universe for astrophysical or cosmological simulations, and (iv) help identifications of host candidates for poorly localized electromagnetic transients, such as gamma-ray bursts observed with the InterPlanetary Network. Both being potential hosts of astrophysical sources of gravitational waves, GLADE includes inactive and active galaxies as well. GLADE was constructed by cross-matching and combining data from five separate (but not independent) astronomical catalogues: GWGC, 2MPZ, 2MASS XSC, HyperLEDA, and SDSS-DR12Q. GLADE is complete up to d_L_=37^+3^_-4_Mpc in terms of the cumulative B-band luminosity of galaxies within luminosity distance dL, and contains all of the brightest galaxies giving half of the total B-band luminosity up to d_L_=91Mpc. As B-band luminosity is expected to be a tracer of binary neutron star mergers (currently the prime targets of joint GW+EM detections), our completeness measures can be used as estimations of completeness for containing all binary neutron star merger hosts in the local Universe.
Exploiting the slitless spectroscopy taken as part of the Grism Lens-Amplified Survey from Space (GLASS), we present an extended analysis of the spatial distribution of star formation in 76 galaxies in 10 clusters at 0.3<z<0.7. We use 85 foreground and background galaxies in the same redshift range as a field sample. The samples are well matched in stellar mass (10^8^-10^11^M_{sun}_) and star formation rate (0.5-50M_{sun}_/yr). We visually classify galaxies in terms of broad band morphology, H{alpha} morphology, and likely physical process acting on the galaxy. Most H{alpha} emitters have a spiral morphology (41%+/-8% in clusters, 51%+/-8% in the field), followed by mergers/interactions (28%+/-8%, 31%+/-7%, respectively) and early-type galaxies (remarkably as high as 29%+/-8% in clusters and 15%+/-6% in the field). A diversity of H{alpha} morphologies is detected, suggesting a diversity of physical processes. In clusters, 30%+/-8% of the galaxies present a regular morphology, mostly consistent with star formation diffused uniformly across the stellar population (mostly in the disk component, when present). The second most common morphology (28%+/-8%) is asymmetric/jellyfish, consistent with ram-pressure stripping or other non-gravitational processes in 18%+/-8% of the cases. Ram-pressure stripping appears significantly less prominent in the field (2%+/-2%), where the most common morphology/mechanism appears to be consistent with minor gas-rich mergers or clump accretion. This work demonstrates that while environment-specific mechanisms affect galaxy evolution at this redshift, they are diverse and their effects are subtle. A full understanding of this complexity requires larger samples and detailed and spatially resolved physical models.
