- ID:
- ivo://CDS.VizieR/J/ApJ/821/L25
- Title:
- Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR)
- Short Name:
- J/ApJ/821/L25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 947 radial velocities of RR Lyrae variable stars in four fields located toward the Galactic bulge, observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR). We show that these RR Lyrae stars (RRLs) exhibit hot kinematics and null or negligible rotation and are therefore members of a separate population from the bar/pseudobulge that currently dominates the mass and luminosity of the inner Galaxy. Our RRLs predate these structures and have metallicities, kinematics, and spatial distribution that are consistent with a "classical" bulge, although we cannot yet completely rule out the possibility that they are the metal-poor tail of a more metal-rich ([Fe/H]~-1dex) halo-bulge population.
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- ID:
- ivo://CDS.VizieR/J/A+A/458/113
- Title:
- BVRIc photometry towards inner Galactic Bulge
- Short Name:
- J/A+A/458/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained BVRI photometry for 21 stellar fields located in directions towards the central 3.5{deg} of the Galaxy. Each field is 10x10 arcmin in size, and a total of ~2x10^5^ stars were measured.
- ID:
- ivo://CDS.VizieR/J/A+A/582/A59
- Title:
- CaIIK spectra of 7 Galactic and MC open clusters
- Short Name:
- J/A+A/582/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The large and small-scale (pc) structure of the Galactic interstellar medium can be investigated by utilising spectra of early- type stellar probes of known distances in the same region of the sky. This paper determines the variation in line strength of CaII at 3933.661{AA} as a function of probe separation for a large sample of stars, including a number of sightlines in the Magellanic Clouds. FLAMES-GIRAFFE data taken with the Very Large Telescope towards early-type stars in 3 Galactic and 4 Magellanic open clusters in CaII are used to obtain the velocity, equivalent width, column density, and line width of interstellar Galactic calcium for a total of 657 stars, of which 443 are Magellanic Cloud sightlines. In each cluster there are between 43 and 111 stars observed. Additionally, FEROS and UVES CaII K and NaI D spectra of 21 Galactic and 154 Magellanic early-type stars are presented and combined with data from the literature to study the calcium column density - parallax relationship.
- ID:
- ivo://CDS.VizieR/J/ApJ/790/164
- Title:
- Candidate bulge WDs in the SWEEPS field
- Short Name:
- J/ApJ/790/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Hubble Space Telescope data of the low-reddening Sagittarius window in the Galactic bulge. The Sagittarius Window Eclipsing Extrasolar Planet Search field (~3'x3'), together with three more Advanced Camera for Surveys and eight Wide-Field Camera 3 fields, were observed in the F606W and F814W filters, approximately every two weeks for 2 yr, with the principal aim of detecting a hidden population of isolated black holes and neutron stars through astrometric microlensing. Proper motions were measured with an accuracy of ~0.1 mas/yr (~4 km/s) at F606W ~25.5 mag, and better than ~0.5 mas/yr (~20 km/s) at F606W ~28 mag, in both axes. Proper-motion measurements allowed us to separate disk and bulge stars and obtain a clean bulge color-magnitude diagram. We then identified for the first time a white dwarf (WD) cooling sequence in the Galactic bulge, together with a dozen candidate extreme horizontal branch stars. The comparison between theory and observations shows that a substantial fraction of the WDs (~30%) are systematically redder than the cooling tracks for CO-core H-rich and He-rich envelope WDs. This evidence would suggest the presence of a significant number of low-mass WDs and WD-main-sequence binaries in the bulge. This hypothesis is further supported by the finding of two dwarf novae in outburst, two short-period (P <~ 1 day) ellipsoidal variables, and a few candidate cataclysmic variables in the same field.
- ID:
- ivo://CDS.VizieR/J/other/RAA/17.62
- Title:
- Candidate members of 4 stellar streams
- Short Name:
- J/other/RAA/17.6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present candidate members of the Pal 5, GD-1, Cetus Polar and Orphan tidal stellar streams found in LAMOST DR3, SDSS DR9 and APOGEE catalogs. In LAMOST DR3, we find 20, 4 and 24 high confidence candidates of tidal streams GD-1, Cetus Polar and Orphan respectively. We also list 59, 118 and 10 high confidence candidates of tidal streams Cetus Polar, Orphan and Pal 5, respectively from the SDSS DR9 spectroscopic catalog. Furthermore, we find seven high confidence candidates of the Pal 5 tidal stream in the APOGEE data. Compared with SDSS, the new candidates from LAMOST DR3 are brighter, so that together, more of the color-magnitude diagram, including the giant branch, can be explored. Analysis of the SDSS data shows that there are three metallicity peaks associated with the Orphan stream which also exhibit some spatial separation. The LAMOST data confirm multiple metallicities in this stream. The metallicity, given by the higher resolution APOGEE instrument, of the Pal 5 tidal stream is [Fe/H]~-1.2, higher than that given earlier by SDSS spectra. Many previously unidentified stream members are tabulated here for the first time, along with existing members, allowing future researchers to further constrain the orbits of these objects as they move within the Galaxy's dark matter potential.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/4112
- Title:
- Candidate RR Lyr star streams in inner Galaxy
- Short Name:
- J/MNRAS/474/4112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the GC3 stream-finding method to RR Lyrae stars (RRLSs) in the Catalina survey. We find 2 RRLS stream candidates at >4{sigma} confidence and another 12 at >3.5{sigma} confidence over the Galactocentric distance range 4<D/kpc<26. Of these, only two are associated with known globular clusters (NGC 1261 and Arp2). The remainder are candidate 'orphan' streams, consistent with the idea that globular cluster streams are most visible close to dissolution. Our detections are likely a lower bound on the total number of dissolving globulars in the inner galaxy, since many globulars have few RRLSs, while only the brightest streams are visible over the Galactic RRLS background, particularly given the current lack of kinematical information. We make all of our candidate streams publicly available and provide a new galstreamspython library for the footprints of all known streams and overdensities in the Milky Way.
- ID:
- ivo://CDS.VizieR/J/ApJS/227/18
- Title:
- Candidate stellar bowshock nebulae from MIR
- Short Name:
- J/ApJS/227/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 709 arc-shaped mid-infrared nebula in 24um Spitzer Space Telescope or 22um Wide Field Infrared Explorer surveys of the Galactic Plane as probable dusty interstellar bowshocks powered by early-type stars. About 20% are visible at 8um or at shorter mid-infrared wavelengths. The vast majority (660) have no previous identification in the literature. These extended infrared sources are strongly concentrated near the Galactic mid-plane, with an angular scale height of ~0.6{deg}. All host a symmetrically placed star implicated as the source of a stellar wind sweeping up interstellar material. These are candidate "runaway" stars potentially having high velocities in the reference frame of the local medium. Among the 286 objects with measured proper motions, we find an unambiguous excess with velocity vectors aligned with the infrared morphology-kinematic evidence that many of these are "runaway" stars with large peculiar motions responsible for the bowshock signature. We discuss a population of "in situ" bowshocks (~103 objects) that face giant HII regions where the relative motions between the star and ISM may be caused by bulk outflows from an overpressured bubble. We also identify ~58 objects that face 8um bright-rimmed clouds and apparently constitute a sub-class of in situ bowshocks where the stellar wind interacts with a photoevaporative flow (PEF) from an eroding molecular cloud interface (i.e., "PEF bowshocks"). Orientations of the acurate nebulae exhibit a correlation over small angular scales, indicating that external influences such as HII regions are responsible for producing some bowshock nebulae. However, the vast majority of the nebulae in this sample appear to be isolated (499 objects) from obvious external influence
- ID:
- ivo://CDS.VizieR/J/A+A/655/A117
- Title:
- Carbon and oxygen in microlensed bulge dwarfs
- Short Name:
- J/A+A/655/A117
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Next to H and He, carbon is, together with oxygen, the most abundant element in the Universe and widely used when modelling the formation and evolution of galaxies and their stellar populations. For the Milky Way bulge, there are currently essentially no measurements of carbon in un-evolved stars, hampering our abilities to properly compare Galactic chemical evolution models to observational data for this still enigmatic stellar population. We aim to determine carbon abundances for our sample of 91 microlensed dwarf and subgiant stars in the Galactic bulge. Together with new determinations for oxygen this forms the first statistically significant sample of bulge stars that have C and O abundances measured, and for which the C abundances have not been altered by the nuclear burning processes internal to the stars. Our analysis is based on high-resolution spectra for a sample of 91 dwarf and subgiant stars that were obtained during microlensing events when the brightnesses of the stars were highly magnified. Carbon abundances were determined through spectral line synthesis of six CI lines around 9100{AA}, and oxygen abundances using the three OI lines at about 7770{AA}. One-dimensional (1D) MARCS model stellar atmospheres calculated under the assumption of local thermodynamic equilibrium (LTE) were used, and non-LTE corrections were applied when calculating the synthetic spectra for both C and O. Carbon abundances was possible to determine for 70 of the 91 stars in the sample and oxygen abundances for 88 of the 91 stars in the sample. The [C/Fe] ratio evolves essentially in lockstep with [Fe/H], centred around solar values at all [Fe/H]. The [O/Fe]-[Fe/H] trend has an appearance very similar to that observed for other alpha-elements in the bulge, with the exception of a continued decrease in [O/Fe] at super-solar [Fe/H], where other alpha-elements tend to level out. When dividing the bulge sample into two sub-groups, one younger than 8Gyr and one older than 8Gyr, the stars in the two groups follow exactly the elemental abundance trends defined by the solar neighbourhood thin and thick disks, respectively. Comparisons with recent models of Galactic chemical evolution in the [C/O]-[O/H] plane show that the models that best match the data are the ones that have been calculated with the Galactic thin and thick disks in mind. We conclude that carbon, oxygen, and the combination of the two support the idea that the majority of the stars in the Galactic bulge have a secular origin; that is, they are formed from disk material. We cannot exclude that a fraction of stars in the bulge could be classified as a classical bulge population, but it would have to be small. More dedicated and advanced models of the inner region of the Milky Way are needed to make more detailed comparisons to the observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/797/21
- Title:
- Carbon-enhanced metal-poor stars
- Short Name:
- J/ApJ/797/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We revisit the observed frequencies of carbon-enhanced metal-poor (CEMP) stars as a function of the metallicity in the Galaxy, using data from the literature with available high-resolution spectroscopy. Our analysis excludes stars exhibiting clear overabundances of neutron-capture elements and takes into account the expected depletion of surface carbon abundance that occurs due to CN processing on the upper red giant branch. This allows for the recovery of the initial carbon abundance of these stars, and thus for an accurate assessment of the frequencies of carbon-enhanced stars. The correction procedure we develop is based on stellar-evolution models and depends on the surface gravity, log g, of a given star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/2653
- Title:
- Carbon stars in the Galaxy and its satellites
- Short Name:
- J/MNRAS/453/2653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We assemble 121 spectroscopically confirmed halo carbon stars, drawn from the literature, exhibiting measurable variability in the Catalina Surveys. We present their periods and amplitudes, which are used to estimate distances from period-luminosity relationships. The location of the carbon stars - and their velocities when available - allow us to trace the streams of the Sagittarius (Sgr) dwarf spheroidal galaxy. These are compared to a canonical numerical simulation of the accretion of Sgr. We find that the data match this model well for heliocentric distances of 15-50kpc, except for a virtual lack of carbon stars in the trailing arm just north of the Galactic plane, and there is only tentative evidence of the leading arm south of the plane. The majority of the sample can be attributed to the Sgr accretion. We also find groups of carbon stars which are not part of Sgr; most of which are associated with known halo substructures. A few have no obvious attribution and may indicate new substructure. We find evidence that there may be a structure behind the Sgr leading stream apocentre, at ~100kpc, and a more distant extension to the Pisces Overdensity also at ~100kpc. We study a further 75 carbon stars for which no good period data could be obtained, and for which NIR magnitudes and colours are used to estimate distances. These data add support for the features found at distances beyond 100kpc.
