- ID:
- ivo://CDS.VizieR/J/ApJ/676/1109
- Title:
- Velocities of stars in the Orion Nebula Cluster
- Short Name:
- J/ApJ/676/1109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from 1351 high-resolution spectra of 1215 stars in the Orion Nebula Cluster (ONC) and the surrounding Orion 1c association, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5m MMT. We confirmed 1111 stars as members, based on their radial velocity and/or H{alpha} emission. The radial velocity distribution of members shows a dispersion of {sigma}=3.1km/s. We found a substantial north-south velocity gradient and spatially coherent structure in the radial velocity distribution, similar to that seen in the molecular gas in the region. We also identified several binary and high velocity stars, a region exhibiting signs of triggered star formation, and a possible foreground population of stars somewhat older than the ONC.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A128
- Title:
- Velocity catalog of A545 galaxies
- Short Name:
- J/A+A/529/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mechanisms giving rise to diffuse radio emission in galaxy clusters, and in particular their connection with cluster mergers, are still debated. We seek to explore the internal dynamics of the cluster Abell 545, which has been shown to host a radio halo. Abell 545 is also peculiar for hosting in its center a very bright, red, diffuse intracluster light due to an old, presumably metal-rich stellar population, so bright to be named as "star pile". Our analysis is mainly based on redshift data for 110 galaxies acquired at the Telescopio Nazionale Galileo. We identify 95 cluster members and analyze the cluster internal dynamics by combining galaxy velocities and positions. We also use both multiband photometric data acquired at the Isaac Newton Telescope and X-ray data from the XMM-Newton Science Archive.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/714
- Title:
- Velocity dispersions of MS1054-03 & Coma galaxies
- Short Name:
- J/ApJ/724/714
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured velocity dispersions ({sigma}) for a sample of 36 galaxies with J<21.2 or M_r_<-20.6mag in MS 1054-03, a massive cluster of galaxies at z=0.83. Our data are of uniformly high quality down to our selection limit, our 16h exposures typically yielding errors of only {delta}({sigma})~10% for L* and fainter galaxies. By combining our measurements with data from the literature, we have 53 cluster galaxies with measured dispersions, and HST/ACS-derived sizes, colors and surface brightness. This sample is complete for the typical L^*^ galaxy at z~1, unlike most previous z~1 cluster samples which are complete only for the massive cluster members (>10^11^M_{sun}_). We find no evidence for a change in the tilt of the fundamental plane (FP).
- ID:
- ivo://CDS.VizieR/J/ApJ/733/46
- Title:
- Velocity measurements in Segue 1
- Short Name:
- J/ApJ/733/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a comprehensive Keck/DEIMOS spectroscopic survey of the ultra-faint Milky Way satellite galaxy Segue 1. We have obtained velocity measurements for 98.2% of the stars within 67pc (10', or 2.3 half-light radii) of the center of Segue 1 that have colors and magnitudes consistent with membership, down to a magnitude limit of r=21.7. Based on photometric, kinematic, and metallicity information, we identify 71 stars as probable Segue 1 members, including some as far out as 87pc. After correcting for the influence of binary stars using repeated velocity measurements, we determine a velocity dispersion of 3.7^+1.4^_-1.1_km/s. The mass within the half-light radius is 5.8^+8.2^_-3.1_x10^5^M_{sun}_. The stellar kinematics of Segue 1 require very high mass-to-light ratios unless the system is far from dynamical equilibrium, even if the period distribution of unresolved binary stars is skewed toward implausibly short periods. With a total luminosity less than that of a single bright red giant and a V-band mass-to-light ratio of 3400M_{sun}_/L_{sun}_, Segue 1 is the darkest galaxy currently known.
- ID:
- ivo://CDS.VizieR/J/A+A/389/795
- Title:
- Vertical structure of edge-on galaxies
- Short Name:
- J/A+A/389/795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To analyze the vertical structure of edge-on galaxies, we have used images of a large uniform sample of flat galaxies that have been taken during the 2MASS all-sky survey. The photometric parameters, such as the radial scale length, the vertical scale height, and the deprojected central surface brightness of galactic disks have been obtained. We find a strong correlation between the central surface brightness and the ratio of the vertical scale height to the vertical scale length: the thinner the galaxy, the lower the central surface brightness of its disk. The vertical scale height does not increase systematically with the distance from the galaxy center in the frames of this sample.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/26
- Title:
- Very Low-Luminosity Objects (VeLLOs) from 1.25-850um
- Short Name:
- J/ApJS/225/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for Very Low-Luminosity Objects (VeLLOs) in the Gould Belt (GB) clouds using infrared and sub-millimeter (sub-mm) data from 1.25 to 850{mu}m and our N_2_H^+^(J=1-0) observations. We modified the criteria by Dunham et al. (2008, J/ApJS/179/249) to select the VeLLOs in the GB clouds, finding 95 VeLLO candidates, 79 of which are newly identified in this study. Out of 95 sources, 44 were detected in both sub-mm continuum and N_2_H^+^ emission and were classified as Group A (the VeLLOs), and 51 sources detected in either sub-mm emission or N_2_H^+^ emission were classified with Group B as candidate VeLLOs. We find that these VeLLOs and the candidates are forming in environments different from those of the likely VeLLOs. Seventy-eight sources are embedded within their molecular clouds, and thus are likely VeLLOs forming in a dense environment. The remaining 17 sources are located in low-level extinction regions (A_V_<1) connected to the clouds, and can be either background sources or candidate substellar objects forming in an isolated mode. The VeLLOs and the candidates are likely more luminous and their envelopes tend to be more massive in denser environments. The VeLLOs and the candidates are more populous in the clouds where more YSOs form, indicating that they form in a manner similar to that of normal YSOs. The bolometric luminosities and temperatures of the VeLLOs are compared to predictions of episodic accretion models, showing that the low luminosities for most VeLLOs can be well explained by their status in the quiescent phases of a cycle of episodic mass accretion.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A13
- Title:
- Very low mass objects in ONC
- Short Name:
- J/A+A/515/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Angular momentum (J) loss requires magnetic interaction between the forming star and both the circumstellar disk and the magnetically driven outflows. In order to test these predictions many authors have investigated a rotation-disk connection in pre-main sequence objects with masses larger than about 0.4M_{sun}_. For brown dwarfs (BDs) this connection was not investigated as yet because there are very few samples available. We aim to extend this investigation well down into the substellar regime for our large sample of ~~80 BDs in the Orion Nebula Cluster, for which we have recently measured rotational periods.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A27
- Title:
- Very low mass stars in Praesepe
- Short Name:
- J/A+A/510/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Determination of the mass functions of open clusters of different ages allows us to infer the efficiency with which brown dwarfs are evaporated from clusters to populate the field. In this paper we present the results of a photometric survey to identify low mass and brown dwarf members of the old open cluster Praesepe (age 590^+150^_-120_Myr, distance 190^+6.0^_-5.8_pc) from which we estimate its mass function and compare this with that of other clusters. We performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric survey of Praesepe covering 3.1{deg}^2^. With 5sigma detection limits of Ic=23.4 and J=20.0, our survey is predicted to be sensitive to objects with masses from 0.6 to 0.05M_{sun}.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A150
- Title:
- 10 very-low-mass stars photometry
- Short Name:
- J/A+A/625/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Measurements of the physical properties of stars at the lower end of the main sequence are scarce. In this context we report masses, radii and surface gravities of ten very-low-mass stars in eclipsing binary systems, with orbital periods of the order of several days. The objects probe the stellar mass-radius relation in the fully convective regime, M*<0.35M_{sun}_, down to the hydrogen burning mass-limit, M_HB_~0.07M_{sun}_. The stars were detected by the WASP survey for transiting extra-solar planets, as low-mass, eclipsing companions orbiting more massive, F- and G-type host stars. We use eclipse observations of the host stars, performed with the TRAPPIST, Leonhard Euler and SPECULOOS telescopes, and radial velocities of the host stars obtained with the CORALIE spectrograph, to determine the physical properties of the low-mass companions. Surface gravities of the low-mass companions are derived from the eclipse and orbital parameters of each system. Spectroscopic measurements of the host star effective temperature and metallicity are used to infer the host star mass and age from stellar evolution models for solar-type stars. Masses and radii of the low-mass companions are then derived from the eclipse and orbital parameters of the binary systems. The objects are compared to stellar evolution models for low-mass stars, to test for an effect of the stellar metallicity and orbital period on the radius of low-mass stars in close binary systems. Measurements are found to be in good agreement with stellar evolution models; a systematic inflation of the radius of low-mass stars with respect to model predictions is limited to 1.6+/-1.2%, in the fully convective low-mass regime. The sample of ten objects indicates a scaling of the radius of low-mass stars with the host star metallicity. No correlation between stellar radii and the orbital periods of the binary systems is determined. A combined analysis with thirteen comparable objects from the literature is consistent with this result.
