- ID:
- ivo://CDS.VizieR/J/A+A/556/A26
- Title:
- Arches cluster: IR phot., extinction and masses
- Short Name:
- J/A+A/556/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Center is the most active site of star formation in the Milky Way Galaxy, where particularly high-mass stars have formed very recently and are still forming today. However, since we are looking at the Galactic Center through the Galactic disk, knowledge of extinction is crucial to study this region. The Arches cluster is a young, massive starburst cluster near the Galactic Center. We observed the Arches cluster out to its tidal radius using Ks-band imaging obtained with NAOS/CONICA at the VLT combined with Subaro/Cisco J-band data to gain a full understanding of the cluster mass distribution. We show that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper-mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, we show that the difference can reach up to 30% for individually derived stellar masses and {Delta}AKs~1 magnitude in acquired Ks-band extinction, while the present mass function slope changes by ~0.17dex. The present-day mass function slope derived assuming the Nishiyama et al. (2009) extinction law increases from a flat slope of {alpha}-Nishi=-1.50+/-0.35 in the core (r<0.2pc) to {alpha}-Nishi=-2.21+/-0.27 in the intermediate annulus (0.2<r<0.4pc), where the Salpeter slope is -2.3. The present-day mass function steepens to {alpha}-Nishi=-3.21+/-0.30 in the outer annulus (0.4<r<1.5pc), indicating that the outer cluster region is depleted of high mass stars. This picture is consistent with mass segregation due to the dynamical evolution of the cluster.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/647/A110
- Title:
- Arches cluster JVLA 6 and 10GHz images
- Short Name:
- J/A+A/647/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high angular resolution radio observations of the Arches cluster in the Galactic centre, one of the most massive young clusters in the Milky Way. The data were acquired in two epochs and at 6 and 10 GHz with the Karl G. Jansky Very Large Array (JVLA). The rms noise reached is 3-4 times better than previous observations and we have almost doubled the number of known radio stars in the cluster. Nine of them have spectral indices consistent with thermal emission from ionised stellar winds. One is a confirmed wind colliding binary and two sources are ambiguous cases. Regarding variability, the radio emission appears to be stable on time scales of a few to ten years. Finally, we have showed that the number of radio stars can be used as a tool for constraining the age or mass of a cluster and also its mass function.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1116
- Title:
- A Spitzer view of NGC 2264
- Short Name:
- J/AJ/138/1116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed mid-IR photometry of the young open cluster NGC 2264 using the images obtained with the Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer instruments and presented a normalized classification scheme of young stellar objects in various color-color diagrams to make full use of the information from multicolor photometry. These results are compared with the classification scheme based on the slope of the spectral energy distribution (SED). From the spatial distributions of Class I and II stars, we have identified two subclusterings of Class I objects in the CONE region of Sung et al. (Cat. J/AJ/135/441). The disked stars in the other star-forming region S Mon are mostly Class II objects. In addition, we have derived a somewhat higher value of the primordial disk fraction for NGC 2264 members located below the main pre-main-sequence locus (so-called BMS stars). This result supports the idea that BMS stars are young stars with nearly edge-on disks.
- ID:
- ivo://CDS.VizieR/J/PASP/116/1012
- Title:
- A star catalog for the open cluster NGC 188
- Short Name:
- J/PASP/116/1012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BVRI broadband photometry for the old open cluster NGC 188, based on an analysis of 299 CCD images either obtained by us, donated by colleagues, or retrieved from public archives.
- ID:
- ivo://CDS.VizieR/J/ApJ/722/605
- Title:
- A stellar rotation census of B stars
- Short Name:
- J/ApJ/722/605
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two recent observing campaigns provide us with moderate dispersion spectra of more than 230 cluster and 370 field B stars. Combining them and the spectra of the B stars from our previous investigations (~430 cluster and ~100 field B stars) yields a large, homogeneous sample for studying the rotational properties of B stars. We derive the projected rotational velocity vsini, effective temperature, gravity, mass, and critical rotation speed V_crit_ for each star. We compare the evolutionary trends of rotation (measured according to the polar gravity of the star) with recent models that treat internal mixing.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/115
- Title:
- Asteroseismic analysis of 8 Kepler red giants
- Short Name:
- J/ApJ/838/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using data from the NASA spacecraft Kepler, we study solar-like oscillations in red giant stars in the open cluster NGC 6811. We determine oscillation frequencies, frequency separations, period spacings of mixed modes, and mode visibilities for eight cluster giants. The oscillation parameters show that these stars are helium-core-burning red giants. The eight stars form two groups with very different oscillation power spectra; the four stars with the lowest {Delta}{nu} values display rich sets of mixed l=1 modes, while this is not the case for the four stars with higher {Delta}{nu}. For the four stars with lowest {Delta}{nu}, we determine the asymptotic period spacing of the mixed modes, {Delta}P, which together with the masses we derive for all eight stars suggest that they belong to the so-called secondary clump. Based on the global oscillation parameters, we present initial theoretical stellar modeling that indicates that we can constrain convective-core overshoot on the main sequence and in the helium-burning phase for these ~2M_{sun}_ stars. Finally, our results indicate less mode suppression than predicted by recent theories for magnetic suppression of certain oscillation modes in red giants.
- ID:
- ivo://CDS.VizieR/J/A+A/381/446
- Title:
- Astrometric Radial Velocities. III.
- Short Name:
- J/A+A/381/446
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Astrometrically determined kinematic data are given for nearby clusters and associations, including astrometric radial velocities and kinematically improved parallaxes for individual stars. The astrometric radial velocities are determined independent of spectroscopy. Table 1 gives the space velocities and internal velocity dispersions of the clusters and associations. The electronic Table1 (Table1.dat) is an extended version of Table 1 in the journal paper, now including the full covariances of the space velocity components as well as the space motion in spherical coordinates. Table 2 gives the astrometric radial velocities and kinematically improved parallaxes for the individual stars. The electronic Table 2 is an extended version of Table 2 in the journal paper, now including all clusters and associations studied; results using data from both the Hipparcos and Tycho-2catalogues, as well as the standard errors for all deduced quantities. The electronic Table 2 is divided into 10 sub-tables (table1a.dat through table2j.dat), one for each cluster or association.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2922
- Title:
- Astrometry and membership in NGC 188
- Short Name:
- J/AJ/126/2922
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present techniques for obtaining precision astrometry using old photographic plates from assorted large-aperture reflectors in combination with recent CCD Mosaic Imager frames. At the core of this approach is a transformation of plate/CCD coordinates into a previously constructed astrometric reference frame around the open cluster NGC 188.
- ID:
- ivo://CDS.VizieR/J/ApJ/718/810
- Title:
- Astrometry and Photometry in the Arches cluster
- Short Name:
- J/ApJ/718/810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep Keck/NIRC2 HK'L' observations of the Arches cluster near the Galactic center reveal a significant population of near-infrared excess sources. We combine the L'-band excess observations with K'-band proper motions, which allow us to confirm cluster membership of excess sources in a starburst cluster for the first time. The robust removal of field contamination provides a reliable disk fraction down to our completeness limit of H=19mag, or ~5M_{sun}_ at the distance of the Arches. Of the 24 identified sources with K'-L'>2.0mag, 21 have reliable proper motion measurements, all of which are proper motion members of the Arches cluster. VLT/SINFONI K'-band spectroscopy of 3 excess sources reveals strong CO bandhead emission, which we interpret as the signature of dense circumstellar disks. The detection of strong disk emission from the Arches stars is surprising in view of the high mass of the B-type main sequence host stars of the disks and the intense starburst environment. We find a disk fraction of 6%+/-2% among B-type stars in the Arches cluster. A radial increase in the disk fraction from 3% to 10% suggests rapid disk destruction in the immediate vicinity of numerous O-type stars in the cluster core. A comparison between the Arches and other high- and low-mass star-forming regions provides strong indication that disk depletion is significantly more rapid in compact starburst clusters than in moderate star-forming environments.
- ID:
- ivo://CDS.VizieR/J/other/NewA/36.70
- Title:
- Astrometry of 3 vdBH open clusters
- Short Name:
- J/other/NewA/36.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a study that combines photometry and astrometry for the open clusters vdB80, vdB85 and vdB130. We apply a model which analyses the proper motion distribution and the stellar density to find the kinematic parameters and stellar membership in the region of the mentioned open clusters. The astrometric data are obtained from UCAC4 catalogue.
