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541. Velocities of individual stars in NGC 205
ID:
ivo://CDS.VizieR/J/AJ/131/332
Title:
Velocities of individual stars in NGC 205
Short Name:
J/AJ/131/332
Date:
21 Oct 2021
Publisher:
CDS
Description:
NGC 205 is the nearest example of a dwarf elliptical galaxy and the prototype of this enigmatic galaxy class. Photometric evidence suggests that NGC 205, a close satellite of the M31 galaxy, is tidally interacting with its parent galaxy. We present stellar radial velocity measurements out to a projected radius of 20' (5kpc) in NGC 205 based on Keck DEIMOS multislit spectroscopic observations of 725 individual red giant branch stars. Our kinematic measurements extend from the center out to 6 times the effective radius of NGC 205, well past the expected tidal radius. The contamination in our kinematic sample from M31 field stars is estimated to be a few percent based on maximum likelihood fits to the distribution of stars in position-velocity space.
542. Velocities of M67 main-sequence and giant stars
ID:
ivo://CDS.VizieR/J/A+A/526/A127
Title:
Velocities of M67 main-sequence and giant stars
Short Name:
J/A+A/526/A127
Date:
21 Oct 2021
Publisher:
CDS
Description:
Precise analyses of stellar radial velocities is able to reveal intrinsic causes of the wavelength shifts of spectral lines (other than Doppler shifts due to radial motion), such as gravitational redshifts and convective blueshifts. Aims. Gravitational redshifts in solar-type main-sequence stars are expected to be some 500m/s greater than those in giants. We search for this difference in redshifts among groups of open-cluster stars that share the same average space motion and thus have the same average Doppler shift.
543. Velocities of red giants in NGC 752
ID:
ivo://CDS.VizieR/J/A+A/339/423
Title:
Velocities of red giants in NGC 752
Short Name:
J/A+A/339/423
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of an 18-year radial-velocity survey of 30 red giants in the field of the open cluster NGC 752 are presented. The membership of 15 stars is confirmed. Four spectroscopic binaries have been discovered among the members and three orbits have been determined for H75, 110 and 208, with periods of 3321, 127 and 5276 days respectively. The binary frequency (27%) is normal. A search for additional members in a wide surrounding area (2{deg}) yielded two possible new members: both are clump red giant candidates. The red giant distribution in the colour-magnitude diagram is somewhat unusual, with a clump containing 8 stars and a second, fainter feature extending to the blue, defined by 3 or 4 stars, which is not accounted for by theoretical isochrones.
544. Velocities of red giants in the SMC
ID:
ivo://CDS.VizieR/J/MNRAS/442/1663
Title:
Velocities of red giants in the SMC
Short Name:
J/MNRAS/442/1663
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from an extensive spectroscopic survey of field stars in the Small Magellanic Cloud (SMC). 3037 sources, predominantly first-ascent red giants, spread across roughly 37.5deg^2^, are analysed. The line-of-sight velocity field is dominated by the projection of the orbital motion of the SMC around the Large Magellanic Cloud/Milky Way. The residuals are inconsistent with both a non-rotating spheroid and a nearly face on disc system. The current sample and previous stellar and Hi kinematics can be reconciled by rotating disc models with line-of-nodes position angle {Theta} ~120{deg}-130{deg}, moderate inclination (25{deg}-70{deg}), and rotation curves rising at 20-40km/s/kpc. The metal-poor stars exhibit a lower velocity gradient and higher velocity dispersion than the metal-rich stars. If our interpretation of the velocity patterns as bulk rotation is appropriate, then some revision to simulations of the SMC orbit is required since these are generally tuned to the SMC disc line of nodes lying in a north-east-south-west (SW) direction. Residuals show strong spatial structure indicative of non-circular motions that increase in importance with increasing distance from the SMC centre. Kinematic substructure in the north-west part of our survey area is associated with the tidal tail or Counter-Bridge predicted by simulations. Lower line-of-sight velocities towards the Wing and the larger velocities just beyond the SW end of the SMC Bar are probably associated with stellar components of the Magellanic-Bridge and Counter-Bridge, respectively. Our results reinforce the notion that the intermediate-age stellar population of the SMC is subject to substantial stripping by external forces.
545. Velocities of RGB stars in the Leo II dwarf galaxy
ID:
ivo://CDS.VizieR/J/AJ/153/254
Title:
Velocities of RGB stars in the Leo II dwarf galaxy
Short Name:
J/AJ/153/254
Date:
21 Oct 2021
Publisher:
CDS
Description:
We combine precision radial velocity data from four different published works of the stars in the Leo II dwarf spheroidal galaxy. This yields a data set that spans 19 years, has 14 different epochs of observation, and contains 372 unique red giant branch stars, 196 of which have repeat observations. Using this multi-epoch data set, we constrain the binary fraction for Leo II. We generate a suite of Monte Carlo simulations that test different binary fractions using Bayesian analysis and determine that the binary fraction for Leo II ranges from 0.30_-0.10_^+0.09^ to 0.34_-0.11_^+0.11^, depending on the distributions of binary orbital parameters assumed. This value is smaller than what has been found for the solar neighborhood (~0.4-0.6) but falls within the wide range of values that have been inferred for other dwarf spheroidals (0.14-0.69). The distribution of orbital periods has the greatest impact on the binary fraction results. If the fraction we find in Leo II is present in low-mass ultra-faints, it can artificially inflate the velocity dispersion of those systems and cause them to appear more dark matter rich than in actuality. For a galaxy with an intrinsic dispersion of 1 km/s and an observational sample of 100 stars, the dispersion can be increased by a factor of 1.5-2 for Leo II-like binary fractions or by a factor of three for binary fractions on the higher end of what has been seen in other dwarf spheroidals.
546. Velocity and light curve analysis of three PPNe
ID:
ivo://CDS.VizieR/J/AJ/156/300
Title:
Velocity and light curve analysis of three PPNe
Short Name:
J/AJ/156/300
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained contemporaneous light, color, and radial velocity data for three proto-planetary nebulae (PPNe) over the years 2007 to 2015. The light and velocity curves of each show similar periods of pulsation, with photometric periods of 42 and 50 days for IRAS 17436+5003, 102 days for IRAS 18095+2704, and 35 days for IRAS 19475+3119. The light and velocity curves are complex with multiple periods and small, variable amplitudes. Nevertheless, at least over limited time intervals, we were able to identify dominant periods in the light, color, and velocity curves and compare the phasing of each. The color curves appear to peak with or slightly after the light curves while the radial velocity curves peak about a quarter of a cycle before the light curves. Similar results were found previously for two other PPNe, although for them the light and color appeared to be in phase. Thus, it appears that PPNe are brightest when smallest and hottest. These phase results differ from those found for classical Cepheid variables, where the light and velocity differ by half a cycle, and are hottest at about average size and expanding. However, they do appear to have similar phasing to the larger-amplitude pulsations seen in RV Tauri variables. Presently, few pulsation models exist for PPNe, and these do not fit the observations well, especially the longer periods observed. Model fits to these new light and velocity curves would allow masses to be determined for these post-AGB objects, and thereby provide important constraints to post-AGB stellar evolution models of low- and intermediate-mass stars.
547. Very metal poor stars in MW halo
ID:
ivo://CDS.VizieR/J/A+A/608/A89
Title:
Very metal poor stars in MW halo
Short Name:
J/A+A/608/A89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of 59 very metal-poor (VMP, -4<=[Fe/H]<~-2) stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo. Our results are based on high-resolution spectroscopic datasets and homogeneous and accurate atmospheric parameters determined in Paper I. We show that once the NLTE effects are properly taken into account, all massive galaxies in our sample, that is, the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax, reveal a similar plateau at [alpha/Fe]=0.3 for each of the alpha-process elements: Mg, Ca, and Ti. We put on a firm ground the evidence for a decline in alpha/Fe with increasing metallicity in the Bootes I ultra-faint dwarf galaxy (UFD), that is most probably due to the ejecta of type Ia supernovae. For Na/Fe, Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable trends with metallicity, suggesting that the processes of Na and Al synthesis are identical in all systems, independent of their mass. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. We show that Sr in the massive galaxies is better correlated with Mg than Fe and that its origin is essentially independent of Ba, for most of the [Ba/H] range. Our three UFDs, that is Bootes I, UMa II, and Leo IV, are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg]=-1.3 and [Ba/Mg]=-1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Bootes I and UMa II indicate a common r-process origin of their neutron-capture elements. Sculptor remains the classical dSph, in which the evidence for inhomogeneous mixing in the early evolution stage, at [Fe/H]<-2, is the strongest.
548. VI and [Fe/H] of Fornax dSph RGB stars
ID:
ivo://CDS.VizieR/J/A+A/459/423
Title:
VI and [Fe/H] of Fornax dSph RGB stars
Short Name:
J/A+A/459/423
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the DART imaging and CaII triplet (CaT) survey of the Fornax dwarf spheroidal galaxy (dSph) at ESO. We collected hundreds of low resolution spectra of Red Giant Branch (RGB) stars in the CaT region, using VLT/FLAMES in Medusa mode, with the GIRAFFE spectrograph (grating LR8, resolving power R~6500). We list the results for the targets with a S/N per Angstrom >10 and an error in velocity <5km/s, because we found this to be the minimum for an accurate determination of velocity and equivalent width. We checked the sample to weed out any spurious object (e.g., broken fibres, background galaxies, foreground stars, spectra not consistent with RGBs). We use a 2.5sigma cut from the system velocity to derive which stars are probable velocity members of the Fornax dSph. We transform the equivalent width of the CaT lines of probable velocity members into metallicity ([Fe/H]) using the relation derived by Rutledge et al. (1997PASP..109..907R) and combining the CaT lines as in Tolstoy et al. (2001MNRAS.327..918T). The errors in [Fe/H] are based on S/N computations and adjusted to agree with repeated measurements.
549. VI photometry of sources in the halo of NGC253
ID:
ivo://CDS.VizieR/J/ApJ/736/24
Title:
VI photometry of sources in the halo of NGC253
Short Name:
J/ApJ/736/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained Magellan/IMACS and HST/ACS imaging data that resolve red giant branch stars in the stellar halo of the starburst galaxy NGC 253. The HST data cover a small area, and allow us to accurately interpret the ground-based data, which cover 30% of the halo to a distance of 30kpc, allowing us to make detailed quantitative measurements of the global properties and structure of a stellar halo outside of the Local Group. The geometry of the halo is significantly flattened in the same sense as the disk, with a projected axis ratio of b/a~0.35+/-0.1. The total stellar mass of the halo is estimated to be M_halo ~2.5+/-1.5x10^9^M_{sun}_, or 6% of the total stellar mass of the galaxy, and has a projected radial dependence that follows a power law of index -2.8+/-0.6, corresponding to a three-dimensional power law index of ~-4. The total luminosity and profile shape that we measure for NGC 253 are somewhat larger and steeper than the equivalent values for the Milky Way and M31, but are well within the scatter of model predictions for the properties of stellar halos built up in a cosmological context. Structure within the halo is seen at a variety of scales: there is small kpc-scale density variation and a large shelf-like feature near the middle of the field. The techniques that have been developed will be essential for quantitatively comparing our upcoming larger sample of observed stellar halos to models of halo formation.
550. V,i,TiOr,CN photometry of And-II AGB stars
ID:
ivo://CDS.VizieR/J/A+A/427/613
Title:
V,i,TiOr,CN photometry of And-II AGB stars
Short Name:
J/A+A/427/613
Date:
21 Oct 2021
Publisher:
CDS
Description:
Our photometric survey of Local Group galaxies, using a four filter technique based on the method of Wing (1971, Proc. Conf. Late-Type Stars, ed. G.W. Lockwood and H.M. Dyck, KPNO Contribution 554, 145) allows the identification and subsequent characterization of their late-type stellar content. Two narrow band filters centred on molecular bands of TiO and CN allow us to distinguish between AGB stars of different chemistries [M-type (O-rich) and C-type (C-rich)]. The faint dwarf spheroidal galaxy And II, a member of the M 31 subgroup, was surveyed. From photometry in V and i as well as in the narrow band filters TiO and CN we were able to identify 7 new AGB carbon stars, to derive their mean absolute <Mi> and bolometric magnitude Mbol, their luminosity function, and their spatial distribution. We are unable to establish the true C/M ratio because the few M stars of And II are overwhelmed by foreground Galactic M st

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