- ID:
- ivo://CDS.VizieR/J/A+A/450/147
- Title:
- IzJHKs photometry of Collinder 359
- Short Name:
- J/A+A/450/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first deep, optical, wide-field imaging survey of the young open cluster Collinder 359, complemented by near-infrared follow-up observations. This study is part of a large programme aimed at examining the dependence of the mass function on environment and time. We have surveyed 1.6 square degrees in the cluster, in the I and z filters, with the CFH12K camera on the Canada-France-Hawaii 3.6-m telescope down to completeness and detection limits in both filters of 22.0 and 24.0mag, respectively. Based on their location in the optical (I-z,I) colour-magnitude diagram, we have extracted new cluster member candidates in Collinder 359 spanning 1.3-0.03M_{sun}_, assuming an age of 60Myr and a distance of 450pc for the cluster. We have used the 2MASS database as well as our own near-infrared photometry to examine the membership status of the optically-selected cluster candidates. Comparison of the location of the most massive members in Collinder 359 in a (B-V,V) diagram with theoretical isochrones suggests that Collinder 359 is older than Alpha Per but younger than the Pleiades. We discuss the possible relationship between Collinder 359 and IC 4665 as both clusters harbour similar parameters, including proper motion, distance, and age.
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- ID:
- ivo://CDS.VizieR/J/A+A/400/891
- Title:
- IZ photometry of Pleiades brown dwarfs
- Short Name:
- J/A+A/400/891
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 6.4 square degrees imaging survey of the Pleiades cluster in the I and Z-bands. The survey extends up to 3{deg} from the cluster center and is 90% complete down to I~=22. It covers a mass range from 0.03M_{sun}_ to 0.48M_{sun}_ and yields 40 brown dwarf candidates (BDCs) of which 29 are new. The spatial distribution of BDCs is fitted by a King profile in order to estimate the cluster substellar core radius. The Pleiades mass function is then derived across the stellar-substellar boundary and we find that, between 0.03M_{sun}_ and 0.48M_{sun}_, it is well represented by a single power-law, dN/dM{prop.to}M^-{alpha}^, with an index alpha=0.60+/-0.11. Over a larger mass domain, however, from 0.03M_{sun}_ to 10M_{sun}_, the mass function is better fitted by a log-normal function. We estimate that brown dwarfs represent about 25% of the cluster population which nevertheless makes up less than 1.5% of the cluster mass. The early dynamical evolution of the cluster appears to have had little effect on its present mass distribution at an age of 120Myr. Comparison between the Pleiades mass function and the Galactic field mass function suggests that apparent differences may be mostly due to unresolved binary systems.
- ID:
- ivo://CDS.VizieR/J/A+A/479/141
- Title:
- Iz photometry, RV and EW(Li) in IC 4665
- Short Name:
- J/A+A/479/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The so-called lithium depletion boundary (LDB) provides a secure and independent tool for deriving the ages of young open clusters. In this context, our goal is to determine membership for a sample of 147 photometrically selected candidates of the young open cluster IC 4665 and to use confirmed members to establish an age based on the LDB. Employing the FLAMES multi-object spectrograph on VLT/UT2, we have obtained intermediate-resolution spectra of the cluster candidates. The spectra were used to measure radial velocities and to infer the presence of the LiI 670.8nm doublet and H{alpha} emission.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1816
- Title:
- JHKLMNOPQ photometry in Orion cluster
- Short Name:
- J/AJ/116/1816
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine our previous optical spectroscopic and photometric analysis of 1600 stars located in the Orion Nebula Cluster (ONC) with our own and published near-infrared photometric surveys of the region in order to investigate the evidence for and properties of circumstellar disks. We use the near-infrared continuum excess as our primary disk diagnostic, although we also study sources with Ca II triplet emission and those designated as "proplyds."
- ID:
- ivo://CDS.VizieR/J/A+A/438/663
- Title:
- JHKL photometry of 30 Dor
- Short Name:
- J/A+A/438/663
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- L-band data of 30 Doradus at 3.5 micron taken with SPIREX (South Pole Infrared Explorer) is presented. The photometry was combined with 2MASS (<II/246>) JHK data at 1.25 -2.2 micron. Colour-colour and colour-magnitude diagrams are constructed and used to determine the sources with infrared excess. These are interpreted as circumstellar disks, and enable the fraction of sources with disks (the cluster disk fraction or CDF) to be determined. We find that ~42% of the sources detected at L-band in 30 Doradus have an IR-excess.
- ID:
- ivo://CDS.VizieR/J/other/ChA+A/28.308
- Title:
- JHK' photometry in GGD 12-15 region
- Short Name:
- J/other/ChA+A/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near infrared imaging observations in JHK broad bands and H_2_ v=1-0 S(1) narrow band of the star formation region GGD12-15 are presented in this article. The images reveal young compact infrared clusters and infrared nebulae in association with infrared sources, as well as outflow activities characterized by H_2_ emission knots. Most of the infrared point sources are invisible in the optical wave band. The JHK' photometric results of 76 infrared point sources contain 32 with infrared excess, and 5 with the characteristics of protostars, indicating very active star formation activities in the molecular clouds.
- ID:
- ivo://CDS.VizieR/J/MNRAS/361/211
- Title:
- JHK photometry of brown dwarfs in Orion
- Short Name:
- J/MNRAS/361/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a deep near-infrared (JHK) survey of the outer parts of the Trapezium Cluster with Gemini South/Flamingos. 396 sources were detected in a 26-arcmin^2^ area, including 138 brown dwarf candidates, defined as M<0.075M_{sun}_ for an assumed age of 1Myr. Only 33 of the brown dwarf candidates are planetary mass candidates with estimated masses in the range 0.003<M<0.012M_{sun}_. In an extinction-limited sample (AV<5) complete to approximately 0.005M_{sun}_ (5M_Jup_) the mass function appears to drop by a factor of 2 at the deuterium burning threshold, i.e. at planetary masses. After allowing for background contamination it is likely that planetary mass objects at 3-13M_Jup_ number <10% of the cluster population, with an upper limit of 13%. Analysis of the spatial distribution of stars and brown dwarf candidates suggests that brown dwarfs and very low-mass stars (M<0.1M_{sun}_) are less likely than more massive stars to have wide (>150AU) binary companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/672/398
- Title:
- JHK' photometry of M17 silhouette object
- Short Name:
- J/ApJ/672/398
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To study how the structure of the envelopes of young stellar objects (YSOs) evolve, we carried out a deep JHK'-band imaging survey of the M17 star-forming region using a near-infrared camera and the Infrared Camera and Spectrograph with adaptive optics mounted on the Subaru Telescope. In this survey, we found 51 dark silhouettes against bright near-infrared nebula emissions as background lights. They are regarded as envelopes associated with YSOs due to their size and association with the YSOs. We derived size, morphology, extinction, and mass for each silhouette envelope.
- ID:
- ivo://CDS.VizieR/J/A+A/375/989
- Title:
- JHK photometry of Praesepe low-mass stars
- Short Name:
- J/A+A/375/989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table 1 contains the list of low-mass Praesepe stars observed with adaptive optics and which were not resolved as multiple systems.
- ID:
- ivo://CDS.VizieR/J/AJ/150/132
- Title:
- JHK photometry of 1203 variables in ONC
- Short Name:
- J/AJ/150/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using UKIRT on Mauna Kea, we have carried out a new near-infrared J, H, K monitoring survey of almost a square degree of the star-forming Orion Nebula Cluster with observations on 120 nights over three observing seasons, spanning a total of 894 days. We monitored ~15000 stars down to J~20 using the WFCAM instrument, and have extracted 1203 significantly variable stars from our data. By studying variability in young stellar objects (YSOs) in the H-K, K color-magnitude diagram, we are able to distinguish between physical mechanisms of variability. Many variables show color behavior indicating either dust-extinction or disk/accretion activity, but we find that when monitored for longer periods of time, a number of stars shift between these two variability mechanisms. Further, we show that the intrinsic timescale of disk/accretion variability in young stars is longer than that of dust-extinction variability. We confirm that variability amplitude is statistically correlated with evolutionary class in all bands and colors. Our investigations of these 1203 variables have revealed 73 periodic AA Tau type variables, many large-amplitude and long-period (P>15 days) YSOs, including three stars showing widely spaced periodic brightening events consistent with circumbinary disk activity, and four new eclipsing binaries. These phenomena and others indicate the activity of long-term disk/accretion variability processes taking place in young stars. We have made the light curves and associated data for these 1203 variables available online.