- ID:
- ivo://CDS.VizieR/J/A+A/488/211
- Title:
- Infrated photometry of NGC 1893
- Short Name:
- J/A+A/488/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The independence of the star formation processes with respect to the environmental conditions is controversial. In particular it is not clear whether star formation in the outer Galaxy, where the environmental conditions are, theoretically, less conducive, occurs in the same way as in the inner Galaxy. We investigate the population of NGC 1893, a young cluster (~3-4Myr) in the outer part of the Galaxy (galactic radius >11kpc) in order to explore the effects of environmental conditions on star forming regions. We present the infrared observations obtained with the IRAC camera on board of the Spitzer Space Telescope and analyze the color-color diagrams to establish the membership of stars with excesses. We also merge this information with that obtained from Chandra ACIS-I observations, in order to identify the Class III population. We find that the cluster is very rich, with 242 PMS Classical T-Tauri stars and 7 Class 0/I stars. Moreover we identify 110 Class III candidate cluster members in the ACIS-I field of view. We estimate a disk fraction for NGC 1893 of about 67%, similar to fraction calculated for nearby star forming regions of the same age. Although the environmental conditions are not favorable, star formation can clearly be very successful in the outer Galaxy, allowing creation of a very rich cluster like NGC 1893.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/869/72
- Title:
- IN-SYNC. VIII. YSOs in NGC 1333, IC 348 and Orion A
- Short Name:
- J/ApJ/869/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we address two issues related to primordial disk evolution in three clusters (NGC1333, IC348, and OrionA) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC348 and OrionA is that primordial disks around intermediate-mass stars (2-5M_{sun}_) evolve faster than those around loss-mass stars (0.1-1M_{sun}_), which is consistent with previous results. However, considering only low-mass stars, we do not find a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories on gas giant planet formation timescales. Second, in the OrionA molecular cloud, in the mass range of 0.35-0.7M_{sun}_, we provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By using surface gravity as an age indicator and employing 4.5{mu}m excess as a primordial disk diagnostic, we observe a trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC1333 and IC348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1{sigma} effect.
- ID:
- ivo://CDS.VizieR/J/A+A/504/681
- Title:
- Integrated BVJHKs for 650 open clusters
- Short Name:
- J/A+A/504/681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the integrated magnitudes and colours of 650 clusters in optical (BV) and the near-infrared (JHKs) passbands and construct the luminosity functions of the Galactic open clusters in these passbands.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1491
- Title:
- Integrated magnitudes of synthetic star clusters
- Short Name:
- J/MNRAS/403/1491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents integrated magnitudes and colours for synthetic clusters. The integrated parameters have been obtained for the whole cluster population as well as for the main-sequence (MS) population of star clusters. We have also estimated observed integrated magnitudes and colours of the MS population of galactic open clusters, Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) star clusters.
- ID:
- ivo://CDS.VizieR/J/A+AS/104/379
- Title:
- Integrated Photometry of open clusters
- Short Name:
- J/A+AS/104/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic open clusters provide an abundant sample of stellar aggregates of various sizes, ages and metal abundances, apt to constitute a template for comparison with star systems in other galaxies. In this paper we present and discuss a standard methodology to synthesize U,B,V fluxes and colours, and apply it to a set of 138 open clusters. Results are compared with previous ones available in the literature. We were able to calibrate a mass-luminosity relation by which we evaluated the mass of ~ 400 open clusters, leading to a well defined present-day mass function. The number-complete sample of galactic open clusters presented in Battinelli & Capuzzo-Dolcetta (1992AJ....103.1596B) is enlarged of a 15%.
- ID:
- ivo://CDS.VizieR/J/ApJ/726/19
- Title:
- Intermediate-mass stars in IC 1805
- Short Name:
- J/ApJ/726/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a study of the intermediate- and high-mass stars in the young, rich star-forming complex IC 1805, based on a combination of optical, near-infrared, and mid-infrared photometry, and classification spectra. These data provide the basis for characterizing the masses and ages for stars more massive than ~2M_{sun}_ and enable a study of the frequency and character of circumstellar disks associated with intermediate- and high-mass stars. Optically thick accretion disks among stars with masses 2<M/M_{sun}_<4 are rare (~2% of members) and absent among more massive stars. A larger fraction (~10%) of stars with masses 2<M/M_{sun}_<4 appear to be surrounded by disks that have evolved from the initial optically thick accretion phase. We identify four classes of such disks. These classes are based on spectral energy distributions (SEDs) of excess emission above photospheric levels: disks that are (1) optically thin based on the magnitude of the observed excess emission from 2 to 24um, (2) optically thin in their inner regions (r<20AU) and optically thick in their outer regions, (3) exhibit empty inner regions (r<10AU) and optically thin emission in their outer regions, and (4) exhibit empty inner regions and optically thick outer regions. We discuss, and assess the merits and liabilities of, proposed explanations for disks exhibiting these SED types and suggest additional observations that would test these proposals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/103
- Title:
- IPHAS T Tauri candidates in IC 1396
- Short Name:
- J/MNRAS/415/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Isaac Newton Telescope (INT) Photometric H-Alpha Survey (IPHAS) is a 1800deg^2^ survey of the Northern Galactic Plane, reaching down to r'~21. We demonstrate how the survey can be used to (1) reliably select classical T Tauri star candidates and (2) constrain the mass accretion rates with an estimated relative uncertainty of 0.6dex. IPHAS is a necessary addition to spectroscopic surveys because it allows large and uniform samples of accretion rates to be obtained with a precise handle on the selection effects. We apply the method on a region of 7deg^2^ towards the HII region IC 1396 in Cepheus OB2 and identify 158 pre-main-sequence candidates with masses between 0.2 and 2.0M_{sun}_ and accretion rates between 10-9.2 and 10-7.0M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/ApJ/659/599
- Title:
- IRAC and JHKs photometry of h and chi Persei
- Short Name:
- J/ApJ/659/599
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe IRAC 3.6-8um observations and ground-based near-IR JHKs photometry from Mimir and 2MASS of the massive double cluster h and chi Persei complete to J=15.5 (M~1.3M_{sun}_). Within 25' of the cluster centers we detect ~11000 sources with J<=15.5, ~7000 sources with [4.5]<=15, and ~5000 sources with [8]<=14.5. In both clusters the surface density profiles derived from the 2MASS data decline with distance from the cluster centers as expected for a bound cluster. Within 15' of the cluster centers, ~50% of the stars lie on a reddened ~13Myr isochrone; at 15'-25' from the cluster centers, ~40% lie on this isochrone. Thus, the optical/2MASS color-magnitude diagrams indicate that h and chi Per are accompanied by a halo population with roughly the same age and distance as the two dense clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/606
- Title:
- IR observations of RCW 121 (IRAS 17149-3916)
- Short Name:
- J/MNRAS/437/606
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep near-infrared broad- and narrow-band imaging and low-resolution spectroscopy of the star formation region RCW 121 (IRAS17149-3916) which we analyse in combination with Herschel (70, 160, 250, 350 and 500 microns) and Spitzer (3.6, 4.5, 5.8 and 8 microns) images. The near-infrared photometry reveals the presence of a stellar cluster of approximate size of 92" which is composed of at least 264 members, approximately 25 per cent of these showing excess emission at wavelengths >2.0 microns, indicative of circumstellar discs. Isochrones corresponding to ages 0.5 to 1.0Myr and A_V_=7.8 fit well the position of a large fraction of likely cluster members in the Ks versus H-Ks diagram. We find three massive star-forming cores located in the boundaries of an expanding HII region ionized by a central O-type star. From their far-infrared spectral energy distributions (SEDs) we derive masses and temperatures of the dense cores. When these young stellar objects (YSOs) have warm emission components, the 1.2 to 500 microns SEDs are fitted with Robitaille et al.'s (2006ApJS..167..256R, 2007ApJS..169..328R) star-disc-envelope model to obtain their physical parameters. The masses of the three YSOs are between 8 and 10M_{sun}_. The youngest site (core I) is undetected at wavelengths <100 microns and is at the earliest evolutionary stage that can currently be detected. The other two cores (II and III) contain YSOs of similar masses and have near-infrared counterparts, which imply a more advanced evolutionary stage. The YSO at core II has been found to have associated a jet, with strong molecular hydrogen line emission, coexisting with a water maser source. RCW 121 is another example of multiple star formation being triggered by the expansion of a single HII region.
- ID:
- ivo://CDS.VizieR/J/ApJ/649/862
- Title:
- IR phot. of IC 348 pre-main-sequence stars
- Short Name:
- J/ApJ/649/862
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 105 stellar rotation periods in the young cluster IC 348, 75 of which are new detections, increasing the total number of known periods in this cluster to 143. The period distribution resembles that seen in the heart of the Orion Nebula cluster by Herbst and colleagues. Stars estimated to be less massive than 0.25M_{sun}_ show a unimodal distribution of fast rotators (P~1-2days) and a tail of slower rotators, while stars estimated to be more massive than 0.25M_{sun}_ show a bimodal distribution with peaks at 2 and 8-days. We combine all published rotation periods in IC 348 with Spitzer mid-IR (3.6, 4.5, 5.8, and 8.0um) photometry, an unprecedentedly efficient and reliable disk indicator, in order to test the disk-braking paradigm.