- ID:
- ivo://CDS.VizieR/V/126
- Title:
- MEGA-H proper motion catalog
- Short Name:
- V/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue MEGA-H is a result of a merging of star lists from the catalogue of stellar proper motions with respect to galaxies in 47 selected areas near the Main Meridional Section of the Galaxy (MEGA-G) (Kharchenko 1987) and from All-sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5) (Cat. <I/280>). Proper motions from the catalogue MEGA-G were reduced to the Hipparcos system by means of common with the ASCC-2.5 stars. The compiled proper motions in the Hipparcos system and their standard errors were computed as the weighted means. Equatorial coordinates are reduced to the equinox J2000 and epoch 1991.25. The catalogue MEGA-H contains 18169 stars. Stars are sorted in right ascension J2000 order.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/853/87
- Title:
- MEGaSaURA. II. Stacked spectra
- Short Name:
- J/ApJ/853/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We stack the rest-frame ultraviolet spectra of N=14 highly magnified gravitationally lensed galaxies at redshifts 1.6<z<3.6. The resulting new composite spans 900<{lambda}_rest_<3000{AA}, with a peak signal-to-noise ratio (S/N) of 103 per spectral resolution element (~100km/s). It is the highest S/N, highest spectral resolution composite spectrum of z~2-3 galaxies yet published. The composite reveals numerous weak nebular emission lines and stellar photospheric absorption lines that can serve as new physical diagnostics, particularly at high redshift with the James Webb Space Telescope (JWST). We report equivalent widths to aid in proposing for and interpreting JWST spectra. We examine the velocity profiles of strong absorption features in the composite, and in a matched composite of z~0 COS/HST galaxy spectra. We find remarkable similarity in the velocity profiles at z~0 and z~2, suggesting that similar physical processes control the outflows across cosmic time. While the maximum outflow velocity depends strongly on ionization potential, the absorption-weighted mean velocity does not. As such, the bulk of the high- ionization absorption traces the low-ionization gas, with an additional blueshifted absorption tail extending to at least -2000km/s. We interpret this tail as arising from the stellar wind and photospheres of massive stars. Starburst99 models are able to replicate this high-velocity absorption tail. However, these theoretical models poorly reproduce several of the photospheric absorption features, indicating that improvements are needed to match observational constraints on the massive stellar content of star-forming galaxies at z~2.
- ID:
- ivo://CDS.VizieR/J/AJ/155/104
- Title:
- MEGaSaURA. I. The sample and the spectra
- Short Name:
- J/AJ/155/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce Project MEGaSaURA: the Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises medium-resolution, rest-frame ultraviolet spectroscopy of N=15 bright gravitationally lensed galaxies at redshifts of 1.68<z<3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range 3200<{lambda}_o_<8280{AA}; the average spectral resolving power is R=3300. The median spectrum has a signal-to- noise ratio (S/N)=21 per resolution element at 5000{AA}. As such, the MEGaSaURA spectra have superior S/N and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum.
2114. Melotte 66
- ID:
- ivo://CDS.VizieR/J/MNRAS/174/471
- Title:
- Melotte 66
- Short Name:
- J/MNRAS/174/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric and photographic photometry of the open cluster Melotte 66 is presented. The CM diagram shows most of the characteristics of an old cluster. The giant branch is broad with its blue edge populated preferentially by stars from the outer parts of the cluster. There is no detectable horizontal subgiant sequence. The main sequence turn-off colour, two-colour diagram and the colour difference between the turn-off and the subgiants are used to estimate the age and composition. Melotte 66 appears to have reddening E(B-V)=0.17mag and ultraviolet excess d(U-B)~0.1mag corresponding to [Fe/H]=-0.3. The cluster is probably between 6 and 7x10^9^yr old. A distance modulus (m-M)o=12.4mag is derived, which implies that the cluster lies about 750pc from the galactic plane.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A85
- Title:
- Membership and lithium of young clusters
- Short Name:
- J/A+A/659/A85
- Date:
- 10 Mar 2022 07:23:16
- Publisher:
- CDS
- Description:
- It is now well known that pre-main sequence models with inflated radii should be taken into account to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern observed in young open star clusters. We test a new set of pre-main sequence models including radius inflation due to the presence of starspots or to magnetic inhibition of convection, using five clusters observed by the Gaia-ESO Survey, spanning the age range ~10-100Myr where such effects could be important. The Gaia-ESO Survey radial velocities are combined with astrometry from Gaia EDR3 to obtain clean lists of high-probability members for the five clusters. A Bayesian maximum likelihood method is adopted to fit the observed cluster sequences to theoretical predictions to derive the best model parameters and the cluster reddening and age. Models are calculated with different values of the mixing length parameter ({alpha}_ML_=2.0, 1.5 and 1.0), for the cases with no spots or with effective spot coverage {beta}_spot_=0.2 and 0.4. The models are also compared with the observed lithium depletion patterns. To reproduce the colour-magnitude diagram and the observed lithium depletion pattern in Gamma Vel A and B and in 25 Ori one needs to assume both a reduced convection efficiency, with {alpha}_ML_=1.0, and an effective surface spot coverage of about 20%. We obtained ages of 18^+1.5^_-4.0_ Myr and 21^+3.5^_-3.0_ Myr for Gamma Vel A and B, respectively, and 19^+1.5^_-7.0_ Myr for 25 Ori. However, a single isochrone is not sufficient to account for the lithium dispersion, and an increasing level of spot coverage as mass decreases seems to be required. On the other hand, the older clusters (NGC 2451B at 30^+3.0^_-5.0_Myr, NGC 2547 at 35^+4.0^_-4.0_Myr, and NGC 2516 at 138^+48^_-42_Myr) are consistent with standard models, with {alpha}_ML_=2.0 and no spots, except at low masses: a 20% spot coverage appears to better reproduce the sequence of M-type stars and might explain the observed spread in lithium abundances. The quality of Gaia-ESO data combined with Gaia allows us to gain important insights on pre-main sequence evolution. Models including starspots can provide a consistent explanation of the cluster sequences and lithium abundances observed in young clusters, although a range of starspot coverage is required to fully reproduce the data.
- ID:
- ivo://CDS.VizieR/J/other/RAA/18.126
- Title:
- Membership catalog for M12 (NGC6218) stars
- Short Name:
- J/other/RAA/18.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using astrometric techniques developed by Anderson et al., we determine proper motions (PMs) in the ~14.60x16.53arcmin^2^ area of the kinematically "thick-disk" globular cluster M12. The cluster's proximity and sparse nature makes it a suitable target for ground-based telescopes. Archive images with time gap of ~11.1-years were observed with the wide-field imager (WFI) mosaic camera mounted on the ESO 2.2m telescope. The median value of PM error in both components is ~0.7mas/yr for the stars having V<=20mag. PMs are used to determine membership probabilities and to separate field stars from the cluster sample. In electronic form, a membership catalog of 3725 stars with precise coordinates, PMs and BV RI photometry is being provided. One of the possible applications of the catalog is demonstrated by gathering the membership information of the variable stars, blue stragglers and X-ray sources reported earlier in the cluster's region.
- ID:
- ivo://CDS.VizieR/J/AJ/159/282
- Title:
- Membership in Ophiuchus & Upper Scorpius complex
- Short Name:
- J/AJ/159/282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a survey for new members of the Ophiuchus cloud complex using high-precision astrometry from the second data release of Gaia, proper motions measured with multi-epoch images from the Spitzer Space Telescope, and color-magnitude diagrams constructed with photometry from various sources. Through spectroscopy of candidates selected with those data, we have identified 155 new young stars. Based on available measurements of kinematics, we classify 102, 47, and 6 of those stars as members of Ophiuchus, Upper Sco, and other populations in Sco-Cen, respectively. We have also assessed the membership of all other stars in the vicinity of Ophiuchus that have spectroscopic evidence of youth from previous studies, arriving at a catalog of 373 adopted members of the cloud complex. For those adopted members, we have compiled mid-infrared photometry from Spitzer and the Wide-field Infrared Survey Explorer and have used mid-infrared colors to identify and classify circumstellar disks. We find that 210 of the members show evidence of disks, including 48 disks that are in advanced stages of evolution. Finally, we have estimated the relative median ages of the populations near the Ophiuchus clouds and the surrounding Upper Sco association using absolute K-band magnitudes (MK) based on Gaia parallaxes. If we adopt an age 10Myr for Upper Sco, then the relative values of MK imply median ages of ~2Myr for L1689 and embedded stars in L1688, 3-4Myr for low-extinction stars near L1688, and ~6Myr for the group containing {rho}Oph.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/111
- Title:
- Members in Serpens Molecular Cloud with Gaia DR2
- Short Name:
- J/ApJ/878/111
- Date:
- 18 Jan 2022 15:09:42
- Publisher:
- CDS
- Description:
- The dense clusters within the Serpens Molecular Cloud are among the most active regions of nearby star formation. In this paper, we use Gaia DR2 parallaxes and proper motions to statistically measure ~1167 kinematic members of Serpens, few of which have been previously identified, to evaluate the star formation history of the complex. The optical members of Serpens are concentrated in three distinct groups located at 380-480pc; the densest clusters are still highly obscured by optically thick dust and have few optical members. The total population of young stars and protostars in Serpens is at least 2000 stars, including past surveys that were most sensitive to protostars and disks, and may be much higher. Distances to dark clouds measured from deficits in star counts are consistent with the distances to the optical star clusters. The Serpens Molecular Cloud is seen in the foreground of the Aquila Rift, dark clouds located at 600-700pc, and behind patchy extinction, here called the Serpens Cirrus, located at ~250pc. Based on the lack of a distributed population of older stars, the star formation rate throughout the Serpens Molecular Cloud increased by at least a factor of 20 within the past ~5Myr. The optically bright stars in Serpens Northeast are visible because their natal molecular cloud has been eroded, not because they were flung outwards from a central factory of star formation. The separation between subclusters of 20-100pc and the absence of an older population together lead to speculation that an external forcing was needed to trigger the active star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A166
- Title:
- Members of 5 cluster in Ori OB1a association
- Short Name:
- J/A+A/631/A166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Orion complex is arguably the most studied star-forming region in the Galaxy. While stars are still being born in the Orion nebula, the oldest part was believed to be no more than 13Myr old. In order to study the full hierarchy of star formation across the Orion complex, we perform a clustering analysis of the Ori OB1a region using new stellar surveys and derive robust ages for each identified stellar aggregate. We use Gaia DR2 parameters supplemented with radial velocities from the GALAH and APOGEE surveys to perform clustering of the Ori OB1a association. Five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). Most correspond to previously known structures (ASCC 16, 25 Orionis, ASCC 20, ASCC 21). We use Gaia DR2, Pan-STARRS1 and 2MASS photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. The ages of the clusters can thus be measured with 10% precision. While four of the clusters have ages between 11 and 13Myr, the ASCC 20 cluster stands out at an age of 21+/-3Myr. This is significantly greater than the age of any previously known component of the Orion complex. To some degree, all clusters overlap in at least one of the six phase-space dimensions. We argue that the formation history of the Orion complex, and its relation to the Gould belt, must be reconsidered. A significant challenge in reconstructing the history of the Ori OB1a association is to understand the impact of the newly discovered 21Myr old population on the younger parts of the complex, including their formation.
2120. Members of IC 2391
- ID:
- ivo://CDS.VizieR/J/A+AS/126/357
- Title:
- Members of IC 2391
- Short Name:
- J/A+AS/126/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New 4-colour BV(RI)_KC_ CCD photometry to a limiting magnitude of V=~19 is presented for 1428 objects observed towards the direction of the young, open cluster IC 2391. We observed 36 (2'x3') fields within 17arcmin of the nominal cluster core. By fitting the theoretical isochrones of D'Antona & Mazzitelli (1994ApJS...90..467D) to a combination of colour-magnitude and colour-colour diagrams, we have identified 17 stars as probable cluster members with a further 85 stars as possible members. The brightness distribution of low-mass members is compared with the luminosity function observed for the Pleiades and we estimate that the contamination due to background giants should be small.
