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- ID:
- ivo://CDS.VizieR/J/A+A/614/A147
- Title:
- NGC 2070 point sources radial velocities
- Short Name:
- J/A+A/614/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We introduce VLT-MUSE observations of the central 2'x2' (30x30pc) of the Tarantula Nebula in the Large Magellanic Cloud. The observations provide an unprecedented spectroscopic census of the massive stars and ionised gas in the vicinity of R136, the young, dense star cluster located in NGC 2070, at the heart of the richest star-forming region in the Local Group. Spectrophotometry and radial-velocity estimates of the nebular gas (superimposed on the stellar spectra) are provided for 2255 point sources extracted from the MUSE datacubes, and we present estimates of stellar radial velocities for 270 early-type stars (finding an average systemic velocity of 271+/-41km/s). We present an extinction map constructed from the nebular Balmer lines, with electron densities and temperatures estimated from intensity ratios of the [SII], [NII], and [SIII] lines. The interstellar medium, as traced by H{alpha} and [NII] {lambda}6583, provides new insights in regions where stars are probably forming. The gas kinematics are complex, but with a clear bi-modal, blue- and red-shifted distribution compared to the systemic velocity of the gas centred on R136. Interesting point-like sources are also seen in the eastern cavity, western shell, and around R136; these might be related to phenomena such as runaway stars, jets, formation of new stars, or the interaction of the gas with the population of Wolf-Rayet stars. Closer inspection of the core reveals red-shifted material surrounding the strongest X-ray sources, although we are unable to investigate the kinematics in detail as the stars are spatially unresolved in the MUSE data. Further papers in this series will discuss the detailed stellar content of NGC 2070 and its integrated stellar and nebular properties.
- ID:
- ivo://CDS.VizieR/J/A+A/372/95
- Title:
- NGC 2439 ubvy{beta} photometry
- Short Name:
- J/A+A/372/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The structure of the field surrounding the Galactic cluster NGC 2439 is studied utilizing uvby{beta} photometry of bright OB stars. We collate all photometric and kinematic data available to identify possible groupings. The stars of our sample show a large scatter in their distances, radial velocities, proper motions and reddenings. We conclude that they do not belong to a single stellar association. We find evidence of the existence of three coherent structures at distances of 370pc, 1kpc, and 2.6-3.2kpc. The high stellar density toward NGC 2439 is very likely due to a decreased absorption in this direction, which poses some doubt on the reality of the cluster. A comprehensive uvby{beta} study of NGC 2439 is required to clarify its nature. The spatial distribution of the stars and their reddening are used to characterise the spatial distribution of the visual extinction in the region. The results obtained confirm previously determined constraints on the formation mechanism of interstellar CH^+^ towards the NGC 2439 field.
- ID:
- ivo://CDS.VizieR/J/A+A/499/483
- Title:
- NIR observations of sources in galactic center
- Short Name:
- J/A+A/499/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study that uses AO assisted observations obtained at the ESO VLT in the NIR H-band and 7 intermediate bands covering the NIR K-band. A comparison of the resulting SEDs with a blackbody of variable extinction then allows us to determine the presence and strength of a CO absorption feature to distinguish between early and late type stars. This new method is suitable for classifying K giants (and later), as well as B2 main sequence (and earlier) stars that are brighter than 15.5mag in the K band in the central parsec. Extremely red objects and foreground sources can also be reliably removed from the sample. Several results, such as the shape of the KLF and the spatial distribution of both early and late type stars, confirm and extend previous works. The distribution of the early type stars can be fitted with a steep power law (beta_1"_=-1.49+/-0.12), alternatively with a broken power law, beta_1-10"_=-1.08+/-0.12, beta_10-20"_=-3.46+/-0.58, since we find a drop in the early type density at ~10". We also detect early type candidates outside of 0.5pc in significant numbers for the first time. The late type density function shows an inversion in the inner 6", with a power-law slope of beta_R<6"_=0.17+/-0.09. The late type KLF has a power-law slope of 0.30+/-0.01, closely resembling the KLF obtained for the bulge of the Milky Way. The early type KLF has a much flatter slope of (0.14+/-0.02). Our results agree best with an in-situ star formation scenario.
- ID:
- ivo://CDS.VizieR/J/A+A/511/A18
- Title:
- NIR observations of stars near SgrA*
- Short Name:
- J/A+A/511/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nuclear star cluster of the Galaxy is an important template for understanding its extragalactic counterparts, which can currently not be resolved into individual stars. Important drawbacks of observations of the Galactic center are, however, the presence of strong and spatially highly variable interstellar extinction and extreme crowding of the sources, which makes the use of adaptive optics techniques necessary. Both points pose serious obstacles to precise photometry that is needed for analyzing the stellar population. The aims of this work are to provide accurate photometry in multiple near-infrared broadband filters, to determine the power-law index of the extinction-law toward the central parsec of the Galaxy, to provide measurements of the absolute extinction toward the Galactic center, and finally to measure the spatial variability of extinction on arcsecond scales.
- ID:
- ivo://CDS.VizieR/J/A+A/486/453
- Title:
- NIR photometry of early-type stars in Cyg OB2
- Short Name:
- J/A+A/486/453
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cygnus OB2 is one of the richest OB associations in the local Galaxy, and is located in a vast complex containing several other associations, clusters, molecular clouds, and HII regions. However, the stellar content of Cygnus OB2 and its surroundings remains rather poorly known largely due to the considerable reddening in its direction at visible wavelength. We investigate the possible existence of an extended halo of early-type stars around Cygnus OB2, which is hinted at by near-infrared color-color diagrams, and its relationship to Cygnus OB2 itself, as well as to the nearby association Cygnus OB9 and to the star forming regions in the Cygnus X North complex. Candidate selection is made with photometry in the 2MASS all-sky point source catalog. The early-type nature of the selected candidates is confirmed or discarded through our infrared spectroscopy at low resolution. In addition, spectral classifications in the visible are presented for many lightly-reddened stars.
- ID:
- ivo://CDS.VizieR/J/A+A/489/229
- Title:
- NIR photometry of IRAS 19410+2336
- Short Name:
- J/A+A/489/229
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS 19410+2336 is a young massive star forming region with an intense outflow activity. Outflows are frequently studied in the near-infrared (NIR) since the H_2_ emission in this wavelength range often traces the shocked molecular gas. However, the mechanisms behind the H_2_ emission detected in IRAS 19410+2336 have not been clarified yet. We present here spatially resolved NIR spectroscopy which allows us to verify whether the H_2_ emission originates from thermal emission in shock fronts or from fluorescence excitation by non-ionizing UV photons. Moreover, NIR spectroscopy also offers the possibility of studying the characteristics of the putative driving source(s) of the H_2_ emission by the detection of photospheric and circumstellar spectral features, and of the environmental conditions (e.g. extinction). We obtained long-slit, intermediate-resolution, NIR spectra of IRAS 19410+2336 using LIRIS, the NIR imager/spectrographer mounted on the 4.2m William Herschel Telescope. As a complement, we also obtained J, H and Ks images with the Las Campanas 2.5m Du Pont Telescope, and archival mid-infrared (MIR) Spitzer-images at 3.6, 4.5, 5.8 and 8.0um.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A117
- Title:
- NIR polarimetry of sources near SgrA*
- Short Name:
- J/A+A/534/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Center offers unique opportunities to study stellar and bow-shock polarization effects in a dusty environment. The goals of this work are to provide near-infrared (NIR) polarimetry of the stellar sources in the central parsec at the resolution of an 8m telescope for the first time, along with new insights into the nature of the known bright bow-shock sources. We use adaptive-optics assisted observations obtained at the ESO VLT in the H- and Ks-band, applying both high-precision photometric methods specifically developed for crowded fields and a newly established polarimetric calibration for NACO to produce polarization maps of the central 3"x10", in addition to spatially resolved polarimetry and a flux variability analysis on the extended sources in this region.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A135
- Title:
- Northern Galactic OB stars vsini
- Short Name:
- J/A+A/562/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation is an important parameter in the evolution of massive stars. Accurate and reliable measurements of projected rotational velocities in large samples of OB stars are crucial to confront the predictions of stellar evolutionary models with observational constraints. We reassess previous determinations of projected rotational velocities (vsini) in Galactic OB stars using a large, high-quality spectroscopic dataset and a strategy that accounts for other sources of line-broadening in addition to rotation. We present a versatile and user-friendly IDL tool - based on a combined Fourier transform (FT) + goodness-of-fit (GOF) methodology - for the line-broadening characterization in OB-type stars. We used this tool to (a) investigate the impact of macroturbulent and microturbulent broadenings on vsini measurements, and (b) determine vsini and the size of the macroturbulent broadening (v_m_) in a sample of ~200 Galactic OB-type stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/42
- Title:
- O and B type stars in W3: first results
- Short Name:
- J/ApJ/813/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from our survey of the star-forming complex W3, combining VRI photometry with multiobject spectroscopy to identify and characterize the high-mass stellar population across the region. With 79 new spectral classifications, we bring the total number of spectroscopically confirmed O- and B-type stars in W3 to 105. We find that the high-mass slope of the mass function in W3 is consistent with a Salpeter IMF, and that the extinction toward the region is best characterized by an R_V_ of approximately 3.6. B-type stars are found to be more widely dispersed across the W3 giant molecular cloud (GMC) than previously realized: they are not confined to the high-density layer (HDL) created by the expansion of the neighboring W4 H ii region into the GMC. This broader B-type population suggests that star formation in W3 began spontaneously up to 8-10 Myr ago, although at a lower level than the more recent star formation episodes in the HDL. In addition, we describe a method of optimizing sky subtraction for fiber spectra in regions of strong and spatially variable nebular emission.
