- ID:
- ivo://CDS.VizieR/J/A+A/507/227
- Title:
- NGC 7129 pre-main sequence stars
- Short Name:
- J/A+A/507/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The reflection nebula NGC 7129 has long been known to be a site of recent star formation as shown, e.g., by the presence of deeply embedded protostars and HH objects. However, studies of the stellar population produced in the star formation process have remained rudimentary. A major step forward has been made with recent Spitzer imaging of the region. This study represents the next step towards a systematic assessment of the pre-main sequence population in NGC 7129. Completeness of the pre-main sequence sample is necessary for studying key features that allow the star-forming process to be understood, such as disk evolution, dynamical evolution, and mass function. At a presumed age of ~3Myr, NGC 7129 is in the critical range where disks around young stars disappear.
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Search Results
282. NGC 7538 region YSOs
- ID:
- ivo://CDS.VizieR/J/MNRAS/467/2943
- Title:
- NGC 7538 region YSOs
- Short Name:
- J/MNRAS/467/2943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep optical photometric data on the NGC 7538 region were collected and combined with archival data sets from the Chandra, 2MASS and Spitzer surveys to generate a new catalogue of young stellar objects (YSOs) including those not showing infrared excess emission. This new catalogue is complete down to 0.8M_{sun}_. The nature of the YSOs associated with the NGC 7538 region and their spatial distribution are used to study the star-formation process and the resultant mass function (MF) in the region. Out of the 419 YSOs, ~91 per cent have ages between 0.1 and 2.5Myr and ~86 per cent have masses between 0.5 and 3.5M_{sun}_, as derived by the spectral energy distribution fitting analysis. Around 24, 62 and 2 per cent of these YSOs are classified to be class I, class II and class III sources, respectively. The X-ray activities for the class I, class II and class III objects are not significantly different from each other. This result implies that the enhanced X-ray surface flux due to the increase in the rotation rate may be compensated for by the decrease in the stellar surface area during the pre-main-sequence evolution. Our analysis shows that the O3V type high-mass star IRS 6 may have triggered the formation of young low-mass stars up to a radial distance of 3pc. The MF shows a turn-off at around 1.5M_{sun}_ and the value of its slope {Gamma} in the mass range 1.5<M/M_{sun}_<6 is -1.76+/-0.24, which is steeper than the Salpeter value.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A10
- Title:
- NGC2264 structure and star formation history
- Short Name:
- J/A+A/609/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. We aim to explore the structure of the open cluster and star-forming region NGC 2264 (~3Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8M_{sun}_ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/140/266
- Title:
- NGC 1333 X-ray luminous YSOs properties
- Short Name:
- J/AJ/140/266
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Chandra X-ray data of the NGC 1333 embedded cluster and combine these data with existing Chandra data, Spitzer photometry, and ground-based spectroscopy of both the NGC 1333 and Serpens cloud core clusters to perform a detailed study of the X-ray properties of two of the nearest embedded clusters to the Sun. We first present new, deeper observations of NGC 1333 with Chandra ACIS-I and combine these with existing Spitzer observations of the region. In NGC 1333, a total of 95 cluster members are detected in X-rays of which 54 were previously identified in the Spitzer data.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A35
- Title:
- NGC 247 young stellar population
- Short Name:
- J/A+A/626/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to investigate the characteristics of the young stellar population in the spiral galaxy NGC 247. In particular, we focused our attention in its hierarchical clustering distributions and the properties of the smallest groups. We used multiband Hubble Space Telescope (HST) data from three fields covering more than half of NGC 247 to select the young population. Then, through the path linkage criterion (PLC), we found compact young star groups and estimated their fundamental parameters, such as their stellar densities, sizes, number of members, and luminosity function (LF) slopes. We also performed a fractal analysis to determinate the clustering properties of this population. We built a stellar density map and dendrograms corresponding to the galactic young population to detect large structures and depict their main characteristics. We detect 339 young star groups, for which we compute a mean radius of ~60pc and a maximum size distribution between 30 and 70pc. We also obtain LF slopes with a bimodal distribution showing peaks at ~0.1 and ~0.2. We identify several candidates for HII regions that follow an excellent spatial correlation with the young groups found by the PLC. We observe that the young populations are hierarchically organized, wherein the smaller and denser structures are within larger and less dense structures. We notice that all these groups present a fractal subclustering, following the hierarchical distribution observed in the corresponding stellar density map. For the large young structures observed in this map, we obtain a fractal dimension of ~1.6-1.8 using the perimeter-area relation and cumulative size distribution. These values are consistent with a scenario of hierarchical star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A30
- Title:
- NGC 3503 YSO candidates
- Short Name:
- J/A+A/565/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here a follow-up study of the molecular gas and dust in the environs of the star forming region NGC 3503. This study aims at dealing with the interaction of the HII region NGC 3503 with its parental molecular cloud, and also with the star formation in the region, that was possibly triggered by the expansion of the ionization front against the parental cloud. To analyze the molecular gas we use CO(J=2-->1), ^13^CO(J=2-->1), C^18^O(J=2-->1), and HCN(J=3-->2) line data obtained with the on-the-fly technique from the APEX telescope. To study the distribution of the dust, we make use of unpublished images at 870um from the ATLASGAL survey and IRAC-GLIMPSE archival images. We use public 2MASS and WISE data to search for infrared candidate young stellar objects (YSOs) in the region.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A7
- Title:
- NH and AV Towards YSOs in the ONC
- Short Name:
- J/A+A/593/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterise the relation between the gas and dust content of the interstellar medium towards young stellar objects in the Orion Nebula Cluster. X-ray observations provide estimates of the absorbing equivalent hydrogen column density NH based on spectral fits. Near-infrared extinction values are calculated from intrinsic and observed colour magnitudes (J-H) and (H-Ks) as given by the VISTA Orion A survey. A linear fit of the correlation between column density and extinction values AV yields an estimate of the N_H_/A_V_ ratio. We investigate systematic uncertainties of the results by describing and (if possible) quantifying the influence of circumstellar material as well as the adopted extinction law, X-ray models, and elemental abundances on the NH/AV ratio. Assuming a Galactic extinction law with R_V=3.1 and solar abundances by Anders et al. (1989), we deduce an N_H_/A_V_ ratio of (1.39+/-0.14)*10^21cm^-2^.mag^-1^ for Class III sources in the Orion Nebula Cluster, where the given error does not include systematic uncertainties. This ratio is consistent with similar studies in other star-forming regions and approximately 31% lower than the Galactic value. We find no obvious trends in the spatial distribution of N_H_/A_V_ ratios. Changes in the assumed extinction law and elemental abundances are demonstrated to have a relevant impact on deduced A_V_ and N_H_ values, respectively. Large systematic uncertainties associated with metal abundances in the Orion Nebula Cluster represent the primary limitation for the deduction of a definitive N_H_/A_V_ ratio and the physical interpretation of these results.
- ID:
- ivo://CDS.VizieR/J/ApJS/211/3
- Title:
- NIR photometry variability in {rho} Oph
- Short Name:
- J/ApJS/211/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Presented are the results of a near-IR photometric survey of 1678 stars in the direction of the {rho} Ophiuchus ({rho} Oph) star forming region using data from the 2MASS Calibration Database. For each target in this sample, up to 1584 individual J-, H-, and Ks-band photometric measurements with a cadence of ~1 day are obtained over three observing seasons spanning ~2.5 yr; it is the most intensive survey of stars in this region to date. This survey identifies 101 variable stars with {Delta}Ks-band amplitudes from 0.044 to 2.31 mag and {Delta}(J-Ks) color amplitudes ranging from 0.053 to 1.47 mag. Of the 72 young {rho} Oph star cluster members included in this survey, 79% are variable; in addition, 22 variable stars are identified as candidate members. Based on the temporal behavior of the Ks time-series, the variability is distinguished as either periodic, long time-scale or irregular. This temporal behavior coupled with the behavior of stellar colors is used to assign a dominant variability mechanism. A new period-searching algorithm finds periodic signals in 32 variable stars with periods between 0.49 to 92 days. The chief mechanism driving the periodic variability for 18 stars is rotational modulation of cool starspots while 3 periodically vary due to accretion-induced hot spots. The time-series for six variable stars contains discrete periodic "eclipse-like" features with periods ranging from 3 to 8 days. These features may be asymmetries in the circumstellar disk, potentially sustained or driven by a proto-planet at or near the co-rotation radius. Aperiodic, long time-scale variations in stellar flux are identified in the time-series for 31 variable stars with time-scales ranging from 64 to 790 days. The chief mechanism driving long time-scale variability is variable extinction or mass accretion rates. The majority of the variable stars (40) exhibit sporadic, aperiodic variability over no discernable time-scale. No chief variability mechanism could be identified for these variable stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/213/22
- Title:
- NIR polarimetry in the Central Molecular Zone
- Short Name:
- J/ApJS/213/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out near-infrared polarimetry toward the boundary of the Central Molecular Zone, in the field of (-1.{deg}4<~l<~-0.{deg}3 and 1.{deg}0<~l<~2.{deg}9,|b|<~0.{deg}1), using the near-infrared polarimetric camera SIRPOL on the 1.4m Infrared Survey Facility telescope. We have selected 112 intrinsically polarized sources on the basis of the estimate of interstellar polarization on Stokes Q/I-U/I planes. The selected sources are brighter than K_S_=14.5mag and have polarimetric uncertainty {delta}P<1%. Ten of these distinctive polarized sources are fit well with spectral energy distributions of young stellar objects when using the photometry in the archive of the Spitzer Space Telescope mid-infrared data. However, many sources have spectral energy distributions of normal stars suffering from heavy interstellar extinction; these might be stars behind dark clouds. Due to the small number of distinctive polarized sources and candidates of young stellar objects, we cannot judge if they are declining in number outside the Central Molecular Zone. Many massive candidates for young stellar objects in the literature have only small intrinsic polarization. This might suggest that their masses are 4-15M_{sun}_, whose intrinsic polarization has been expected to be small.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/10
- Title:
- NIR properties of YSO in the CCCP
- Short Name:
- J/ApJS/194/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Great Nebula in Carina (NGC 3372) is the best target to study in detail the process of violent massive star formation and the resulting feedback effects of cloud dispersal and triggered star formation. While the population of massive stars is rather well studied, the associated low-mass stellar population was largely unknown up to now. The near-infrared study in this paper builds on the results of the Chandra Carina Complex Project, that detected 14368 X-ray sources in the 1.4deg^2^ survey region, an automatic source classification study that classified 10714 of these X-ray sources as very likely young stars in Carina, and an analysis of the clustering properties of the X-ray-selected Carina members. In order to determine physical properties of the X-ray-selected stars, most of which were previously unstudied, we used HAWK-I at the ESO Very Large Telescope to conduct a very deep near-IR survey with subarcsecond angular resolution, covering an area of about 1280arcmin^2^. The HAWK-I images reveal more than 600000 individual infrared sources, whereby objects as faint as J~23, H~22, and Ks~21 are detected at signal-to-noise ratio (S/N)>=3. While less than half of the Chandra X-ray sources have counterparts in the Two Micron All Sky Survey catalog, the ~5mag deeper HAWK-I data reveal infrared counterparts to 6636 (=88.8%) of the 7472 Chandra X-ray sources in the HAWK-I field. We analyze near-infrared color-color and color-magnitude diagrams to derive information about the extinctions, infrared excesses (as tracers for circumstellar disks), ages, and masses of the X-ray-selected objects.
