- ID:
- ivo://CDS.VizieR/J/AJ/143/149
- Title:
- NIR spectroscopy of Galactic Wolf-Rayet stars. II.
- Short Name:
- J/AJ/143/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are continuing a J, K and narrowband imaging survey of 300{deg}^2^ of the plane of the Galaxy, searching for new Wolf-Rayet (W-R) stars. Our survey spans 150{deg} in Galactic longitude and reaches 1{deg} above and below the Galactic plane. The survey has a useful limiting magnitude of K=15 over most of the observed Galactic plane, and K=14 (due to severe crowding) within a few degrees of the Galactic center. Thousands of emission-line candidates have been detected. In spectrographic follow-ups of 146 relatively bright W-R star candidates, we have re-examined 11 previously known WC and WN stars and discovered 71 new W-R stars, 17 of type WN and 54 of type WC. Our latest image analysis pipeline now picks out W-R stars with a 57% success rate. Star subtype assignments have been confirmed with the K-band spectra and distances approximated using the method of spectroscopic parallax. Some of the new W-R stars are among the most distant known in our Galaxy. The distribution of these new W-R stars is beginning to trace the locations of massive stars along the distant spiral arms of the Milky Way.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/2858
- Title:
- NIR spectroscopy of Galactic WR stars. III
- Short Name:
- J/MNRAS/452/2858
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new method of image subtraction is applied to images from a J, K, and narrow-band imaging survey of 300 deg2 of the plane of the Galaxy, searching for new Wolf-Rayet (WR) stars. Our survey spans 150{deg} in Galactic longitude and reaches b=+/-1{deg} with respect to the Galactic plane. The survey has a useful limiting magnitude of K=15 over most of the observed Galactic plane, and K=14 (due to severe crowding) within a few degrees of the Galactic Centre. The new image subtraction method described here (better than aperture or even point-spread-function photometry in very crowded fields) detected several thousand emission-line candidates. In 2011 and 2012 June and July, we spectroscopically followed up on 333 candidates with MDM-TIFKAM and Infrared Telescope Facility (IRTF)-SpeX, discovering 89 emission-line sources. These include 49 WR stars, 43 of them previously unidentified, including the most distant known Galactic WR stars, more than doubling the number on the far side of the Milky Way. We also demonstrate our survey's ability to detect very faint planetary nebulae and other NIR emission objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/117
- Title:
- NIR stellar populations in Sextans A and Leo A
- Short Name:
- J/ApJ/854/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present JHKs observations of the metal-poor ([Fe/H]{<}-1.40) dwarf-irregular galaxies, Leo A and Sextans A, obtained with the WIYN High-resolution Infrared Camera at Kitt Peak. Their near-IR stellar populations are characterized by using a combination of color-magnitude diagrams and by identifying long-period variable stars. We detected red giant and asymptotic giant branch stars, consistent with membership of the galaxy's intermediate-age populations (2-8Gyr old). Matching our data to broadband optical and mid-IR photometry, we determine luminosities, temperatures, and dust-production rates (DPR) for each star. We identify 32 stars in LeoA and 101 stars in Sextans A with a DPR>10^-11^M_{sun}_/yr, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The total rates of dust injection into the interstellar medium of Leo A and Sextans A are (8.2+/-1.8)x10^-9^M_{sun}_/yr and (6.2+/-0.2)x10^-7^M_{sun}/yr, respectively. The majority of this dust is produced by a few very dusty evolved stars and does not vary strongly with metallicity.
- ID:
- ivo://CDS.VizieR/J/AJ/120/2206
- Title:
- NTT, HDF-S and HDF-N photometric redshifts
- Short Name:
- J/AJ/120/2206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and compare in this paper new photometric redshift catalogs of the galaxies in three public fields: the NTT Deep Field, the HDF-N, and the HDF-S. In the case of the NTT Deep Field, we present here a new photometric catalog, obtained by combining the existing BVrI and JKs with new deep U observations acquired with NTT-SUSI2, and which includes also the contiguous field centered on the z_em_=4.7 quasar BR 1202-0
- ID:
- ivo://CDS.VizieR/J/AJ/105/499
- Title:
- OB Associations and Spiral Structure in M33
- Short Name:
- J/AJ/105/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This file contains UBV photometry for the brightest stars in the southern spiral arm of M33. All stars brighter than V=21 are included in this file. For details on the observations and data reduction see reference. All the data is in ASCII format of the file. The observations where carried out on the Palomar 60in. telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/454/151
- Title:
- OB Associations of the Northern Milky Way
- Short Name:
- J/ApJ/454/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the massive star content of Milky Way clusters and OB associations in order to answer three questions: (1) How coeval is star formation? (2) How constant is the initial mass function (IMF)? (3) What is the progenitor mass of Wolf-Rayet stars? Our sample includes NGC 6823/Vul OB1, NGC 6871/Cyg OB3, Berkeley 86/Cyg OB1, NGC 6913/Cyg OB1, NGC 7235, NGC 7380/Cep OB1, Cep OB5, IC 1805/Cas OB6, NGC 1893/Aur OB2, and NGC 2244/Mon OB2. Large-field CCD imaging and multiobject, fiber spectroscopy has resulted in UBV photometry for >10,000 stars and new spectral types for ~200 stars. These data are used to redetermine distances and reddenings for these regions and to help exclude probable nonmembers in constructing the H-R diagrams. We reanalyze comparable data previously published on Cyg OB2, Tr 14/16, and NGC 6611 and use all of these to paint a picture of star formation and to measure the IMFs. We find the following: (1) Most of the massive stars are born during a period Delta(Tau) < 3 Myr in each association. Some star formation has clearly preceded this event, as evidenced by the occasional presence of evolved (Tau ~ 10 Myr) 15 Msun stars despite a typical age Tau ~ 2 Myr for the more massive population. However, all these regions also show evidence of 5-10 Msun pre-main-sequence stars (Tau < 1 Myr), demonstrating that some star formation at lower masses does continue for at least 1 Myr after the formation of high-mass stars. (2) There is no statistically significant difference in IMF slopes among these clusters, and the average value is found to be Gamma = -1.1 +/- 0.1 for stars with masses > 7 Msun. A comparison with similarly studied OB associations in the Magellanic Clouds reveals no difference in IMF slope, and hence we conclude that star formation of massive stars in clusters proceeds independently of metallicity, at least between z = 0.02 and z = 0.002. The masses of the highest mass stars are approximately equal in the Milky Way, LMC, and SMC associations, contrary to the expectation that this value should vary by a factor of 3 over this metallicity range. We conclude that radiation pressure on grains must not limit the mass of the highest mass star that can form, in accord with the suggestion of Wolfire & Cassinelli that the mere existence of massive stars suggests that shocks or other mechanisms have disrupted grains in star-forming events. (3) The four Wolf-Rayet stars in our sample have come from stars more massive than 40 Msun; one WC star and one late-type WN star each appear to have come from very massive (~100 Msun) progenitors.
- ID:
- ivo://CDS.VizieR/J/ApJS/2/389
- Title:
- Observations of O and B stars
- Short Name:
- J/ApJS/2/389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog of O and B stars contains magnitudes, colors, spectral types and polarization for 1259 stars. In addition to observations, the catalogue contains the derived absorption and distance modulus. A photoelectric photometer attached to the 82-inch (2m) reflector of the McDonald Observatory was used for the polarization observations. The photometric UBV observations were made over a period of 4 years with the 13-inch (33cm) and the 82-inch telescopes at McDonald. The spectroscopic classification was made with a new camera installed on the Cassegrain spectrograph, with a dispersion of 86{AA}/mm at H{delta}.
- ID:
- ivo://CDS.VizieR/J/PAZh/30/37
- Title:
- Observations of supernovae in 1997-1999
- Short Name:
- J/PAZh/30/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric observations of 15 supernovae discovered in the period 1997-1999 are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/538/A142
- Title:
- OB stars in NGC 6334 and NGC 6357
- Short Name:
- J/A+A/538/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star-forming complexes are large structures exhibiting massive star-formation at different stages of evolution, from dense cores to well-developed HII regions. They are very interesting for the study of the formation and evolution of stars. NGC 6334 and NGC 6357 are two active and relatively nearby star-forming complexes. From the extinction map and the sub-mm cold dust emission, and because they have similar velocities, these regions are most likely connected. However, located in the direction of the Galactic center their radial velocity is not representative of their distance. An alternative is then to determine the distance of NGC 6334 and NGC 6357 from their stellar content. Our aim is to perform a census of O-B3 ionising stars in NGC 6334 and NGC 6357, to determine the extinction coefficient, and the distance of both regions. A census of O-B3 stars is an essential basis for estimating the statistical lifetime of the earliest massive star-forming phases.
- ID:
- ivo://CDS.VizieR/J/AcA/50/307
- Title:
- OGLE LMC BVI photometry
- Short Name:
- J/AcA/50/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the BVI photometric maps of the Large Magellanic Cloud. They contain BVI photometry and astrometry of more than 7 million stars from the central parts of the LMC. The data were collected during the second phase of the OGLE microlensing project. We discuss the accuracy of the data and present color-magnitude diagrams of all 26 fields observed by OGLE in the LMC. The BVI maps of the LMC are accessible electronically for the astronomical community from the OGLE Internet archive.
