- ID:
- ivo://CDS.VizieR/J/MNRAS/458/L59
- Title:
- Draco II stars gi magnitude & radial velocities
- Short Name:
- J/MNRAS/458/L59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first spectroscopic analysis of the faint and compact stellar system Draco II (Dra II, M_V_=-2.9+/-0.8,r_h_=19^+8^_-6_pc), recently discovered in the Panoramic Survey Telescope and Rapid Response System 1 3{PI} survey. The observations, conducted with DEIMOS on the Keck II telescope, establish some of its basic characteristics: the velocity data reveal a narrow peak with nine member stars at a systemic heliocentric velocity <v_r_>=-347.6^+1.7^_-1.8_km/s, thereby confirming Dra II is a satellite of the Milky Way; we infer a velocity dispersion with {sigma}_vr_=2.9+/-2.1km/s (<8.4km/s at the 95 per cent confidence level), which implie log_10_(M_1/2_)-5.5^+0.4^_-0.6_ and log_10_((M/L_)1/2_)=2.7^+0.5^_-0.8_, in Solar units; furthermore, very weak calcium triplet lines in the spectra of the high signal-to-noise member stars imply [Fe/H]<-2.1, whilst variations in the line strengths of two stars with similar colours and magnitudes suggest a metallicity spread in Dra II. These new data cannot clearly discriminate whether Draco II is a star cluster or amongst the faintest, most compact, and closest dwarf galaxies. However, the sum of the three - individually inconclusive - pieces of evidence presented here seems to favour the dwarf galaxy interpretation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/375/831
- Title:
- Draco MegaCam, INT and HST photometry
- Short Name:
- J/MNRAS/375/831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Draco dwarf spheroidal galaxy (dSph), with its apparent immense mass-to-light ratio and compact size, holds many clues to the nature of the enigmatic dark matter. Here we present deep photometric studies of this dwarf galaxy, undertaken with the MegaCam Camera at the Canada-France-Hawaii Telescope, the Wide Field Camera at the Isaac Newton Telescope and the Wide Field and Planetary Camera onboard the Hubble Space Telescope (HST). The new photometric data cover the entirety of the galaxy, and reach i'=24.5 at 50 per cent completeness, significantly deeper than previous panoramic studies, allowing searches for tidal disturbances of much lower surface brightness than has been possible before. With these improved statistics, we find no evidence for asymmetric disturbances or tidal tails that possess more than 3 per cent of the stars found within the centre of the galaxy. We find that the central stellar density, as probed by the HST data, rises into the central 0.5arcmin. Uncertainties in the position of the centroid of the galaxy do not allow us to determine whether the apparent flattening of the profile interior to 0.5arcmin is reliable or not. Draco is therefore a flawless dwarf galaxy, featureless and apparently unaffected by Galactic tides.
853. DRaGONS survey
- ID:
- ivo://CDS.VizieR/J/ApJ/649/63
- Title:
- DRaGONS survey
- Short Name:
- J/ApJ/649/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from the Distant Radio Galaxies Optically Non-detected in the SDSS (DRaGONS) survey. Using a novel selection technique for identifying high-redshift radio galaxy (HzRG) candidates, a large sample is compiled using bright (S_1.4GHz_>100mJy) radio sources from the FIRST survey having no optical counterpart in the SDSS. Near-IR K-band imaging for 96 targets allows preliminary identification of HzRG candidates through the well-known K-z relation, for subsequent spectroscopic observation. We measure magnitudes brighter than K~19.5 for 70 of the 96, and limiting magnitudes for the remainder. Redshifts based on a linear fit to the K-z diagram give a mean <z>=2.5 and median z=2.0, showing that this method should be efficient at identifying a large number of HzRGs.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1689
- Title:
- DRAO ELAIS N1 catalog
- Short Name:
- J/ApJ/714/1689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of deep polarization imaging at 1.4GHz with the Dominion Radio Astrophysical Observatory as part of the DRAO Planck Deep Fields project. This deep extragalactic field covers 15.16deg^2^ centered at RA(J2000)=16:14 and DE(J2000)=54:56, has an angular resolution of 42"x62" at the field center, and reaches a sensitivity of 55uJy/beam in Stokes I and 45uJy/beam in Stokes Q and U. We detect 958 radio sources in Stokes I of which 136 are detected in polarization. We present the Euclidean-normalized polarized differential source counts down to 400uJy. These counts indicate that sources have a higher degree of fractional polarization at fainter Stokes I flux density levels than for brighter sources, confirming an earlier result. We find that the majority of our polarized sources are steep-spectrum objects with a mean spectral index of -0.77, and there is no correlation between fractional polarization and spectral index. We also matched deep field sources to counterparts in the Faint Images of the Radio Sky at Twenty Centimeters catalog. Of the polarized sources, 77% show structure at the arcsecond scale whereas only 38% of the sources with no detectable polarization show such structure. The median fractional polarization for resolved sources is 6.8%, while it is 4.4% for compact objects. The polarized radio sources in our deep field are predominantly those sources which are resolved and show the highest degrees of fractional polarization, indicating that the lobe dominated structure may be the source of the highly polarized sources. These resolved radio galaxies dominate the polarized source counts at P_0_=(Q^2^+U^2^)^0.5^<3mJy.
- ID:
- ivo://CDS.VizieR/VIII/55
- Title:
- DRAO Penticton P-survey Database
- Short Name:
- VIII/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains 1692 radio sources observed with the Penticton synthesis telescope at 408 MHz and at 1420 MHz. The catalog is comprised of sources detected in the P-surveys 1P through 9P, 12P through 15P, and 20P through 27P (see the "References" section below). The database was provided by R.Roger & C.R.Purton in May 1990 and an update of the data with further P-surveys is currently in progress.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/10
- Title:
- 3D shapes of extremely metal-poor galaxies
- Short Name:
- J/ApJ/883/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The three-dimensional (3D) shape of a galaxy inevitably is tied to how it has formed and evolved and to its dark matter halo. Local extremely metal-poor galaxies (XMPs; defined as having an average gas-phase metallicity <0.1 solar) are important objects for understanding galaxy evolution largely because they appear to be caught in the act of accreting gas from the cosmic web, and their 3D shape may reflect this. Here, we report on the 3D shape of XMPs as inferred from their observed projected minor-to-major axial ratios using a hierarchical Bayesian inference model, which determines the likely shape and orientation of each galaxy, while simultaneously inferring the average shape and dispersion. We selected a sample of 149 XMPs and divided it into three subsamples according to physical size and found that (1) the stellar component of XMPs of all sizes tends to be triaxial, with an intermediate axis ~0.7 times the longest axis and that (2) smaller XMPs tend to be relatively thicker, with the shortest axis going from ~0.15 times the longest axis for the large galaxies to ~0.4 for the small galaxies. We provide the inferred 3D shape and inclination of the individual XMPs in electronic format. We show that our results for the intermediate axis are not clouded by a selection effect against face-on XMPs. We discuss how an intermediate axis significantly smaller than the longest axis may be produced by several mechanisms, including lopsided gas accretion, non-axisymmetric star formation, or coupling with an elongated dark matter halo. Large relative thickness may reflect slow rotation, stellar feedback, or recent gas accretion.
- ID:
- ivo://CDS.VizieR/J/A+A/455/107
- Title:
- 3D spectroscopy with VLT/GIRAFFE
- Short Name:
- J/A+A/455/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A precise derivation of the evolution of the Tully-Fisher is crucial to understand the interplay between dark matter and baryonic matter in cosmological models, using 15 deployable integral field units of FLAMES/GIRAFFE at VLT, we have recovered the velocity fields of 35 galaxies at intermediate redshift (0.4<z<0.75). This facility is able to recover the velocity fields of almost all the emission line galaxies with I_AB_<=22.5 and W_0_(OII)>=15{AA}. In our sample, we find only 35% rotating disks. These rotating disks produce a Tully-Fisher relationship (stellar mass or MK versus Vmax which has apparently not evolved in slope, zero point and scatter since z=0.6). The only evolution found is a brightening of the B band luminosity of a third of the disks, possibly due to an enhancement of the star formation. The very large scatters found in previously reported Tully-Fisher relationships at moderate redshifts are caused by the numerous (65%) galaxies with perturbed or complex kinematics. Those galaxies include minor or major mergers, merger remnants and/or inflow/outflows and their kinematics can be easily misidentified by slit spectroscopy. Their presence suggests a strong evolution in the dynamical properties of galaxies during the last 7Gyr.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A127
- Title:
- 13 dsph and ultra-faint galaxies analysis
- Short Name:
- J/A+A/641/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large homogeneous set of stellar parameters and abundances across a broad range of metallicities, involving 13 classical dwarf spheroidal (dSph) and ultra-faint dSph (UFD) galaxies. In total, this study includes 380 stars in Fornax, Sagittarius, Sculptor, Sextans, Carina, Ursa Minor, Draco, Reticulum II, Bootes I, Ursa Major II, Leo I, Segue I, and Triangulum II. This sample represents the largest, homogeneous, high-resolution study of dSph galaxies to date. With our homogeneously derived catalog, we are able to search for similar and deviating trends across different galaxies. We investigate the mass dependence of the individual systems on the production of alpha-elements, but also try to shed light on the long-standing puzzle of the dominant production site of r-process elements. We used data from the Keck observatory archive and the ESO reduced archive to reanalyze stars from these 13 classical dSph and UFD galaxies. We automatized the step of obtaining stellar parameters, but ran a full spectrum synthesis (1D, local thermal equilibrium) to derive all abundances except for iron to which we applied nonlocal thermodynamic equilibrium corrections where possible. The homogenized set of abundances yielded the unique possibility of deriving a relation between the onset of type Ia supernovae and the stellar mass of the galaxy. Furthermore, we derived a formula to estimate the evolution of alpha-elements. This reveals a universal relation of these systems across a large range in mass. Finally, we show that between stellar masses of 2.1x10^7^M_{sun}_ and 2.9x10^5^M_{sun}_ , there is no dependence of the production of heavy r-process elements on the stellar mass of the galaxy. Placing all abundances consistently on the same scale is crucial to answering questions about the chemical history of galaxies. By homogeneously analyzing Ba and Eu in the 13 systems, we have traced the onset of the s-process and found it to increase with metallicity as a function of the galaxy's stellar mass. Moreover, the r-process material correlates with the alpha-elements indicating some coproduction of these, which in turn would point toward rare core-collapse supernovae rather than binary neutron star mergers as a host for the r-process at low [Fe/H] in the investigated dSph systems.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A71
- Title:
- dSph RGB abundance and velocities
- Short Name:
- J/A+A/606/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From ESO VLT/FLAMES/GIRAFFE spectra, abundance measurements of Zn have been made in ~100 individual red giant branch (RGB) stars in the Sculptor dwarf spheroidal galaxy. This is the largest sample of individual Zn abundance measurements within a stellar system beyond the Milky Way. In the observed metallicity range, -2.7<=[Fe/H]<=-0.9, the general trend of Zn abundances in Sculptor is similar to that of {alpha}-elements. That is, super-solar abundance ratios of [Zn/Fe] at low metallicities, which decrease with increasing [Fe/H], eventually reaching subsolar values. However, at the higher metallicities in Sculptor, [Fe/H]>~-1.8, we find a significant scatter, -0.8<~[Zn/Fe]<~+0.4, which is not seen in any {alpha}-element. Our results are consistent with previous observations of a limited number of stars in Sculptor and in other dwarf galaxies. These results suggest that zinc has a complex nucleosynthetic origin, behaving neither completely like an {alpha}- nor an iron-peak element.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/7
- Title:
- dSph satellites of M31. I. Variables in And XIX
- Short Name:
- J/ApJ/779/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present B, V time-series photometry of Andromeda XIX (And XIX), the most extended (half-light radius of 6.2') of Andromeda's dwarf spheroidal companions, which we observed with the Large Binocular Cameras at the Large Binocular Telescope. We surveyed a 23'x23' area centered on And XIX and present the deepest color-magnitude diagram (CMD) ever obtained for this galaxy, reaching, at V~26.3mag, about one magnitude below the horizontal branch (HB). The CMD shows a prominent and slightly widened red giant branch, along with a predominantly red HB, which extends to the blue to significantly populate the classical instability strip. We have identified 39 pulsating variable stars, of which 31 are of RR Lyrae type and 8 are Anomalous Cepheids (ACs). Twelve of the RR Lyrae variables and three of the ACs are located within And XIX's half light radius. The average period of the fundamental mode RR Lyrae stars (<P_ab_>{=}0.62days, {sigma}=0.03days) and the period-amplitude diagram qualify And XIX as an Oosterhoff-Intermediate system. From the average luminosity of the RR Lyrae stars (<V(RR)>=25.34mag, {sigma}=0.10mag), we determine a distance modulus of (m-M)_0_=24.52+/-0.23mag in a scale where the distance to the Large Magellanic Cloud (LMC) is 18.5+/-0.1mag. The ACs follow a well-defined Period-Wesenheit (PW) relation that appears to be in very good agreement with the PW relationship defined by the ACs in the LMC.
