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4411. NGC 1960 IRAC and MIPS photometry
ID:
ivo://CDS.VizieR/J/MNRAS/420/2884
Title:
NGC 1960 IRAC and MIPS photometry
Short Name:
J/MNRAS/420/2884
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of Spitzer IRAC (3.6-8um) and MIPS (24um) imaging of members of the 16^+10^_-5_ Myr old open cluster NGC 1960 (M36). Models of terrestrial planet formation indicate that rocky planets are likely to achieve their final masses at around 10-30Myr, and thus this cluster is at an interesting epoch for planet formation. We find 21 B-F5 type stars and 14 F6-K9 type stars which have 24um excess emission, and thus determine that >30 per cent of B-F5 type stars and >23 per cent of F6-K9 type stars in this cluster have 24um excess emission. These excess frequencies are similar to those observed in other clusters of similar age. Three early-type stars have excesses at near-infrared wavelengths. Analysis of their spectral energy distributions confirms that these are true debris discs and not remnant primordial or transitional discs. None of the 61 Sun-like stars has confirmed near-infrared excess, and we can place a limit on the frequency of 8um excess emission around Sun-like stars of <7 per cent. All of the detected excesses are consistent with emission from debris discs and are not primordial.
4412. NGC 7538 IRS 1-3 and IRS 9 sources
ID:
ivo://CDS.VizieR/J/MNRAS/443/3218
Title:
NGC 7538 IRS 1-3 and IRS 9 sources
Short Name:
J/MNRAS/443/3218
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep and high-resolution (FWHM~0.4-arcsec) near-infrared (NIR) imaging observations of the NGC 7538 IRS 1-3 region (in JHK bands), and IRS 9 region (in HK bands) using the 8.2m Subaru telescope. The NIR analysis is complemented with Giant Metrewave Radio Telescope (GMRT) low-frequency observations at 325, 610, and 1280MHz, molecular line observations of H^13^CO^+^ (J=1-0), and archival Chandra X-ray observations. Using the 'J-H/H-K' diagram, 144 Class II and 24 Class I young stellar object (YSO) candidates are identified in the IRS 1-3 region. Further analysis using 'K/H-K' diagram yields 145 and 96 red sources in the IRS 1-3 and IRS 9 regions, respectively. A total of 27 sources are found to have X-ray counterparts. The YSO mass function (MF), constructed using a theoretical mass-luminosity relation, shows peaks at substellar (~0.08-0.18M_{sun}_) and intermediate (~1-1.78M_{sun}_) mass ranges for the IRS 1-3 region. The MF can be fitted by a power law in the low-mass regime with a slope of {Gamma} ~0.54-0.75, which is much shallower than the Salpeter value of 1.35. An upper limit of 10.2 is obtained for the star to brown dwarf ratio in the IRS 1-3 region. GMRT maps show a compact HII region associated with the IRS 1-3 sources, whose spectral index of 0.87+/-0.11 suggests optical thickness. This compact region is resolved into three separate peaks in higher resolution 1280MHz map, and the 'east' subpeak coincides with the IRS 2 source. H^13^CO^+^ (J=1-0) emission reveals peaks in both IRS 1-3 and IRS 9 regions, none of which are coincident with visible nebular emission, suggesting the presence of dense cloud nearby. The virial masses are approximately of the order of 1000 and 500M_{sun}_ for the clumps in IRS 1-3 and IRS 9 regions, respectively.
4413. NGC 1333 low-mass stars infrared photometry
ID:
ivo://CDS.VizieR/J/AJ/127/1131
Title:
NGC 1333 low-mass stars infrared photometry
Short Name:
J/AJ/127/1131
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of near-infrared imaging and low-resolution near-infrared spectroscopy of low-mass objects in the NGC 1333 molecular cloud. A JHK survey of an 11.4'x11.7' area of the northern cluster was conducted to a sensitivity of K<=16mag. Using near-infrared magnitudes and colors from this and previously published surveys, 25 brown dwarf candidates were selected toward the high-extinction cloud core. Spectra in the K band were obtained and comparisons of the depths of water vapor absorption bands in our candidate objects with a grid of dwarf, subgiant, and giant standards were made to derive spectral types. These data were then used to derive effective temperatures and stellar luminosities that, when combined with theoretical tracks and isochrones for pre-main-sequence objects, resulted in estimates for their masses and ages.
4414. NGC 3923 MegaCam image
ID:
ivo://CDS.VizieR/J/A+A/588/A77
Title:
NGC 3923 MegaCam image
Short Name:
J/A+A/588/A77
Date:
21 Oct 2021
Publisher:
CDS
Description:
The elliptical galaxy NGC 3923 is known to be surrounded by a number of stellar shells, probable remnants of an accreted galaxy. Despite its uniqueness, the deepest images of its outskirts come from the 1980s. On the basis of the modified Newtonian dynamics (MOND), it has recently been predicted that a new shell lies in this region. We obtain the deepest image ever of the galaxy, map the tidal features in it, and search for the predicted shell. The image of the galaxy was taken by the MegaCam camera at the Canada-France-Hawaii Telescope in the g'-band. It reached the surface-brightness limit of 29mag/arcsec^2^. In addition, we reanalyzed an archival HST image of the galaxy.
4415. NGC6530 member parameters from Gaia-ESO survey
ID:
ivo://CDS.VizieR/J/A+A/623/A159
Title:
NGC6530 member parameters from Gaia-ESO survey
Short Name:
J/A+A/623/A159
Date:
21 Oct 2021
Publisher:
CDS
Description:
In very young clusters, stellar age distribution is the empirical proof of the duration of star formation (SF) and of the physical mechanisms involved in the process. We derived accurate stellar ages for the cluster NGC6530, associated with the Lagoon Nebula to infer its SF history. We use the Gaia-ESO survey observations and Gaia DR2 data, to derive cluster membership and fundamental stellar parameters. We identified 652 confirmed and 9 probable members. The reddening inferred for members and non-members allows us to distinguish MS stars and giants, in agreement with the distances inferred from Gaia DR2 data. The foreground and background stars show a spatial pattern that traces the 3D structure of the nebular dust component. We derive stellar ages for 382 confirmed cluster members and we find that the gravity-sensitive gamma index distribution for M stars is correlated with stellar age. For all members with Teff<5500K, the mean logarithmic age is 5.84 (units of years) with a dispersion of 0.36dex. The age distribution of stars with accretion and/or disk (CTTSe) is similar to that of stars without accretion and without disk (WTTSp). We interpret this dispersion as evidence of a real age spread since the total uncertainties on age determinations, derived from Monte Carlo simulations, are significantly smaller than the observed spread. This conclusion is supported by the evidence of a decreasing of the gravity-sensitive gamma index as a function of stellar ages. The presence of the age spread is also supported by the spatial distribution and the kinematics of old and young members. In particular, members with accretion and/or disk, formed in the last 1Myr, show evidence of subclustering around the cluster center, in the Hourglass Nebula and in the M8-E region, suggesting a possible triggering of star formation events by the O-type star ionization fronts.
4416. NGC 2516 membership list
ID:
ivo://CDS.VizieR/J/A+A/641/A51
Title:
NGC 2516 membership list
Short Name:
J/A+A/641/A51
Date:
21 Oct 2021
Publisher:
CDS
Description:
We wish to measure the cool star rotation period distribution for the Pleiades-age rich open cluster NGC 2516 and use it to determine whether cluster-to-cluster variations exist in otherwise identical open clusters. We obtained 42d-long time-series CCD photometry of NGC 2516 in the V and Ic filters using the Yale 1m telescope at CTIO and performed a number of related analyses, including PSF-based time-series photometry. Our data are complemented with additional information from several photometric datasets, literature radial velocities, and Gaia DR2 astrometry. All available data are used to construct an integrated membership list for NGC 2516, containing 844 stars in our ~1 degree field of view. We derived 308 rotation periods for late-F to mid-M cluster members from our photometry. We identified an additional 247 periodic M dwarf stars from a prior study as cluster members, and used these to construct a 555-star rotation period distribution for NGC 2516. The colour-period diagram (in multiple colours) has almost no outliers and exhibits the anticipated triangular shape, with a diagonal slow rotator sequence that is preferentially occupied by the warmer stars along with a flat fast rotator sequence that is preferentially populated by the cooler cluster members. We also find a group of extremely slowly rotating M dwarfs (10d<P<23d), forming a branch in the colour-period diagram which we call the 'extended slow rotator sequence'. This, and other features of the rotational distribution can also be found in the Pleiades, making the colour-period diagrams of the two clusters nearly indistinguishable. A comparison with the well-studied (and similarly aged) open cluster M 35 indicates that the cluster's rotational distribution is also similarly indistinguishable from that of NGC 2516. Those for the open clusters M 50 and Blanco 1 are similar, but data issues for those clusters make the comparisons somewhat more ambiguous. Nevertheless, we demonstrate the existence of a representative zero-age main sequence (ZAMS) rotational distribution and provide a simple colour-independent way to represent it. We perform a detailed comparison of the NGC 2516 rotation period data with a number of recent rotational evolution models. Using X-ray data from the literature, we also construct the first rotation-activity diagram for solar-type stars in NGC 2516, one that we find is essentially indistinguishable from those for the Pleiades and Blanco 1. The two clusters NGC 2516 and Pleiades can be considered twins in terms of stellar rotation and related properties (and M 35, M 50, and Blanco 1 are similar), suggesting that otherwise identical open clusters also have intrinsically similar cool star rotation and activity distributions.
4417. NGC 1750 & 1758 membership probabilities
ID:
ivo://CDS.VizieR/J/A+A/337/125
Title:
NGC 1750 & 1758 membership probabilities
Short Name:
J/A+A/337/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
Cluster-field segregation and determination of physical parameters of the open clusters NGC 1750 and NGC 1758 were performed from CCD and photographic photometric and astrometric surveys previously published by the authors. Membership probabilities were computed to a brightness limit of R=15mag through a non-standard method in a fully non-parametric approach, using proper motions, positions and photometry. This study allowed several parameters for NGC 1750 and NGC 1758 to be determined, including position, size, density profile, absorption, distance, age, luminosity function and mass. The common colour excess of both clusters is E(B-V)=0.34mag. NGC 1750 is slightly younger (log(t)=8.3), closer (V-M_v_=9.0mag) and less concentrated than NGC 1758 (log(t)=8.60 and V-M_v_=9.4mag). We also conclude that NGC 1746 is an erroneous assignation (not corresponding to any real open cluster), and that NGC 1750 and NGC 1758 are overlapping clusters, but they do not constitute a gravitationally bounded system.
4418. NGC 2264 members periods with CoRoT
ID:
ivo://CDS.VizieR/J/MNRAS/430/1433
Title:
NGC 2264 members periods with CoRoT
Short Name:
J/MNRAS/430/1433
Date:
21 Oct 2021
Publisher:
CDS
Description:
Rotation is one of the key stellar parameters which undergo substantial evolution during the stellar lifetime, in particular during the early stages. Stellar rotational periods can be determined on the basis of the periodic modulation of starlight produced by non-uniformities on the surface of the stars, due to manifestation of stellar activity. We present the results of an extensive search for rotational periods among NGC 2264 cluster members, based on photometric monitoring using the COnvection ROtation and planetary Transits (CoRoT) satellite, with particular attention to the distribution of classical and weak-line T-Tauri stars. NGC 2264 is one of the nearest and best studied star forming region in the solar neighbourhood, with an estimated age of 3Myr, and is the object of a recent simultaneous multiband campaign including a new CoRoT observation with the aim to assess the physical origin of the observed variability. We find that the rotational distributions of classical and weak-line T-Tauri stars are different, suggesting a difference in the rotational properties of accreting and non-accreting stars.
4419. NGC 4649 (M60) globular clusters
ID:
ivo://CDS.VizieR/J/MNRAS/355/608
Title:
NGC 4649 (M60) globular clusters
Short Name:
J/MNRAS/355/608
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Sloan g and i imaging from the Gemini Multi-object Spectrograph (GMOS) instrument on the Gemini North telescope for the globular cluster (GC) system around the Virgo galaxy NGC 4649 (M60). Our three pointings, taken in good seeing conditions, cover an area of about 90 square arcmin. We detect 2151 unresolved sources. Applying colour and magnitude selection criteria to this source list gives 995 candidate GCs. Our source list is greater than 90 per cent complete to a magnitude of i=23.6, and has little contamination from background galaxies. We find fewer than half a dozen potential ultracompact dwarf galaxies around NGC 4649.
4420. NGC6357 686 molecular cores physical properties
ID:
ivo://CDS.VizieR/J/A+A/647/A154
Title:
NGC6357 686 molecular cores physical properties
Short Name:
J/A+A/647/A154
Date:
21 Oct 2021
Publisher:
CDS
Description:
We mapped the NGC6357 star forming region at 450 and 850 micron with SCUBA-2 and in the CO(3-2) line with HARP at the JCMT. We also retrieved Herschel Hi-GAL data at 70 and 160 micron. The submm continuum emission was decomposed into cores with the algorithm Gaussclumps (Stutzki & Guesten, 1990ApJ...356..513S). By fitting greybodies to the core 4-point SEDs we derived their temperature and mass. Core mass functions were derived in the region more exposed to the FUV flux from massive stars (associated with the HII regions G353.2+0.9, G353.1+0.6, and G353.2+0.7) and in the region less exposed. Table 2 lists the physical properties of the cores in NGC6357.