- ID:
- ivo://CDS.VizieR/J/AJ/127/1117
- Title:
- Halpha emission-line stars in NGC2264
- Short Name:
- J/AJ/127/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep survey of H{alpha} emission-line stars in the NGC 2264 region using wide-field objective prism films. We find 357 H{alpha} emission-line stars, of which 113 were previously detected, within an area of 3{deg}x3{deg} centered on the Cone Nebula, with a majority of stars being concentrated in a dense cluster at the center of the region. We present a large-scale CO map of NGC 2264 and find a strong correlation between the cluster of H{alpha} emission-line stars and the most massive core in the cloud complex. A more extended halo of stars poorly correlated with the gas may represent stars that have drifted away from their birth place, suggesting that star formation has taken place in NGC 2264 for several million years.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/669/L33
- Title:
- H{alpha} emission sources in h and {chi} Per
- Short Name:
- J/ApJ/669/L33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of accretion disks associated with ~13Myr old intermediate/low-mass stars in h and {chi} Persei. Optical spectroscopy of ~5000 stars in these clusters and a surrounding halo population reveal 32 A-K stars with Halpha emission. Matching these stars with 2MASS and optical photometry yields 25 stars with the highest probability of cluster membership and EW(Halpha)>=5{AA}. Sixteen of these sources have EW(Halpha)>=10{AA}.
- ID:
- ivo://CDS.VizieR/J/AJ/143/3
- Title:
- H{alpha} emission stars in IC 1274
- Short Name:
- J/AJ/143/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IC 1274 is a faintly luminous nebula lying on the near surface of the Lynds 227 (L227) molecular cloud. Its cavity-like morphology is reminiscent of a blistered star-forming region. Four luminous, early-type (B0-B5) stars are located within a spherical volume ~5' in diameter that appears to be clear of heavy obscuration. Approximately centered in the cleared region is the B0 V star HD 166033, which is thought to be largely responsible for the cavity's excavation. Over 80 H{alpha} emission sources brighter than V~21 have been identified in the region. More than half of these are concentrated in IC 1274 and are presumably members of a faint T Tauri star population. Chandra Advanced CCD Imaging Spectrometer imaging of a nearby suspected pulsar and time-variable {gamma}-ray source (GeV J1809-2327) detected 21 X-ray sources in the cluster vicinity, some of which are coincident with the early-type stars and H{alpha} emitters in IC 1274. Deep (V~22) optical BVRI photometry has been obtained for the cluster region. A distance of 1.82+/-0.3kpc and a mean extinction of AV~1.21+/-0.2mag follow from photometry of the early-type stars. Using pre-main-sequence evolutionary models, we derive a median age for the H{alpha} emitters and X-ray sources of ~1Myr; however, a significant dispersion is present. The displaced material was driven against what remains of the molecular cloud to the east, enabling the formation of the substantial number of T Tauri stars found there. A dispersed population of H{alpha} emitters is also found along the periphery of L227, IC 1275, and IC 4684.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1530
- Title:
- H{alpha} emission stars in LDN988
- Short Name:
- J/AJ/131/1530
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- L988 is a large (~0.5{deg}x0.7{deg}) dark cloud complex at about 600pc that contains several bright pre-main-sequence objects (such as V1331 Cyg and LkH{alpha} 321), but this paper deals in detail only with a small region on its eastern edge, near the HAeBe star LkH{alpha} 324. That star and its distant companion LkH{alpha} 324SE lie at the apex of a V-shaped area apparently excavated from the edge of L988, and are the brightest members of a small cluster containing about 50 H{alpha}-emission stars.
- ID:
- ivo://CDS.VizieR/J/A+A/613/L5
- Title:
- H{alpha} emitting sources around MWC758
- Short Name:
- J/A+A/613/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- MWC758 is a young star surrounded by a transitional disk. The disk shows an inner cavity and spiral arms that could be caused by the presence of protoplanets. Recently, a protoplanet candidate has been detected around MWC758 through high-resolution L'-band observations. The candidate is located inside the disk cavity at a separation of 111 mas from the central star, and at an average position angle of 165.5{deg}. We aim at detecting accreting protoplanet candidates within the disk of MWC758 through spectral angular differential imaging observations in the optical regime. In particular, we explore the emission at the position of the detected planet candidate. We have performed simultaneous adaptive optics observations in the H{alpha} line and the adjacent continuum using SPHERE/ZIMPOL at the Very Large Telescope (VLT). The data analysis does not reveal any H{alpha} signal around the target. The derived contrast curve in the B_Ha filter allows us to derive a 5{sigma} upper limit of 7.6mag at 111mas, the separation of the previously detected planet candidate. This contrast translates into a H{alpha} line luminosity of LH{alpha}<~5*10^-5^L_{sun}_ at 111mas. Assuming that LH{alpha} scales with Lacc as in Classical T Tauri stars as a first approximation, we can estimate an accretion luminosity of Lacc<3.7*10^-4^L_{sun}_ for the protoplanet candidate. For the predicted mass range of MWC758b, 0.5-5M_Jup_, this implies accretion rates smaller than dM/dt<3.4*(10^-8^-10^-9^)M_[sun}_/yr, for an average planet radius of 1.1 RJup. Therefore, our estimates are consistent with the predictions of accreting circumplanetary accretion models for R_in_=1R_Jup_. The ZIMPOL line luminosity is consistent with the H{alpha} upper limit predicted by these models for truncation radii <~3.2R_Jup_. The non-detection of any H{alpha}emitting source in the ZIMPOL images does not allow us to unveil the nature of the L' detected source. Either it is a protoplanet candidate or a disk asymmetry.
- ID:
- ivo://CDS.VizieR/J/ApJ/677/169
- Title:
- H{alpha} galaxies at z=0.84
- Short Name:
- J/ApJ/677/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an H{alpha} near-infrared narrowband survey searching for star-forming galaxies at redshift z=0.84. This work is an extension of our previous narrowband studies in the optical at lower redshifts. After removal of stars and redshift interlopers (using spectroscopic and photometric redshifts), we build a complete sample of 165 H{alpha} emitters in the extended Groth strip and GOODS-N fields with L(H{alpha})>10^41^ergs/s. We compute the H{alpha} luminosity function at z=0.84 after corrections for [NII] flux contamination, extinction, systematic errors, and incompleteness. Our sources present an average dust extinction of A(H{alpha})=1.5mag. Adopting H{alpha} as a surrogate for the instantaneous SFR, we measure an extinction-corrected SFR density of 0.17^+0.03^_-0.03_M_{sun}_/yr/Mpc^3^. Combining this result to our prior measurements at z=0.02, 0.24, and 0.40, we derive an H{alpha}-based evolution of the SFR density proportional to (1+z)^{beta}^ with {beta}=3.8+/-0.5. This evolution is consistent with that derived by other authors using different SFR tracers.
- ID:
- ivo://CDS.VizieR/J/AJ/143/61
- Title:
- H{alpha} spectroscopy in IC 1396 HII region
- Short Name:
- J/AJ/143/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made an extensive survey of emission-line stars in the IC 1396 H II region to investigate the low-mass population of pre-main-sequence (PMS) stars. A total of 639 H{alpha} emission-line stars were detected in an area of 4.2deg^2^ and their i' photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the H II region (Rim B and SFO 37, 38, 39, 41), and near HD206267, which is the main exciting star of the HII region. Based on the extinction estimated from the near-infrared color-color diagram, we have selected PMS star candidates associated with IC1396. The age and mass were derived from the extinction-corrected color-magnitude diagram and theoretical PMS tracks. Most of our PMS candidates have ages of <3Myr and masses of 0.2-0.6M_{sun}_. Although it appears that only a few stars were formed in the last 1Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered the formation of many low-mass stars at the dense inhomogeneity in and around the HII region by a radiation-driven implosion.
- ID:
- ivo://CDS.VizieR/J/ApJS/208/28
- Title:
- H{alpha} survey in the ONC
- Short Name:
- J/ApJS/208/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an H{alpha} emission line survey in a 1 deg^2^ area centered on the Orion Nebula Cluster, obtained with the Wide Field Grism Spectrograph 2 on the 2.2 m telescope of the University of Hawaii. We identified 587 stars with H{alpha} emission, 99 of which, located mainly in the outer regions of the observed area, have not appeared in previous H{alpha} surveys. We determined the equivalent width (EW) of the line and, based on this, classified 372 stars as classical T Tauri stars (CTTSs) and 187 as weak-line T Tauri stars (WTTSs). Simultaneous r', i' photometry indicates a limiting magnitude of r' ~ 20 mag, but the sample is incomplete at r' > 17 mag. The surface distribution of the H{alpha} emission stars reveals a clustered population and a dispersed population, the former consisting of younger and more massive young stars than the latter. Comparison of the derived EWs with those found in the literature indicates variability of the H{alpha} line. We found that the typical amplitudes of the variability are not greater than a factor of two to three in most cases. We identified a subgroup of low-EW stars with infrared signatures indicative of optically thick accretion disks. We studied the correlations between the EW and other properties of the stars. Based on literature data, we examined several properties of our CTTS and WTTS subsamples and found significant differences in mid-infrared color indices, average rotational periods, and spectral energy distribution characteristics of the subsamples.
- ID:
- ivo://CDS.VizieR/J/AJ/122/248
- Title:
- h and chi Per UBVI,H{alpha} photometry
- Short Name:
- J/AJ/122/248
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVI and H{alpha} photometry is presented for 17319 stars in vicinity of the young double cluster h and {chi} Persei. Our photometry extends over a 37'x1{deg} field centered on the association. We construct reddening contours within the imaged field. We find that the two clusters share a common distance modulus of 11.75+/-0.05 and ages of log[age(yr)]=7.1+/-0.1. From the V-H{alpha} color, a measure of the H{alpha} emission strength, we conduct a survey for emission line objects within the association. We detect a sample of 33 Be stars, eight of which are new detections. We present a scenario of evolutionary enhancement of the Be phenomenon to account for the peak in Be fraction toward the top of the main sequence in the population of h and {chi} Persei and similar young clusters. UBVI and H{alpha} photometry was performed on five nights between 1999 August 17 and 25 at the San Diego State University Mount Laguna Observatory with the 1m telescope and a Loral 2048x2048 CCD.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A26
- Title:
- H and Ks photometry of Trumpler 14
- Short Name:
- J/A+A/515/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present adaptive optics (AO) near-infrared observations of the core of the Tr 14 cluster in the Carina region obtained with the ESO multi-conjugate AO demonstrator, MAD. Our campaign yields AO-corrected observations with an image quality of about 0.2' across the 2" field of view, which is the widest AO mosaic ever obtained. We detected almost 2000 sources spanning a dynamic range of 10 mag. The pre-main sequence (PMS) locus in the colour-magnitude diagram is well reproduced by Palla & Stahler isochrones with an age of 3 to 5x10^5^yr, confirming the very young age of the cluster. We derive a very high (deprojected) central density n_0_~4.5(+/-0.5)x10^4^pc^-3^ and estimate the total mass of the cluster to be about ~4.3^+3.3^_-1.5_x10^3^M_{sun}_, although contamination of the field of view might have a significant impact on the derived mass. We show that the pairing process is largely dominated by chance alignment so that physical pairs are difficult to disentangle from spurious ones based on our single epoch observation. Yet, we identify 150 likely bound pairs, 30% of these with a separation smaller than 0.5" (~1300AU). We further show that at the 2{sigma} level massive stars have more companions than lower-mass stars and that those companions are respectively brighter on average, thus more massive. Finally, we find some hints of mass segregation for stars heavier than about 10M_{sun}_. If confirmed, the observed degree of mass segregation could be explained by dynamical evolution, despite the young age of the cluster.
