- ID:
- ivo://CDS.VizieR/J/ApJ/766/114
- Title:
- Water and methanol masers in G75.78+0.34
- Short Name:
- J/ApJ/766/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present subarcsecond observations toward the massive star-forming region G75.78+0.34. We used the Very Large Array to study the centimeter continuum and H_2_O and CH_3_OH maser emission, and the Owens Valley Radio Observatory and Submillimeter Array to study the millimeter continuum and recombination lines (H40{alpha} and H30{alpha}). We found radio continuum emission at all wavelengths, coming from three components: (1) a cometary ultracompact (UC) H II region with an electron density ~3.7x10^4^/cm3, excited by a B0 type star, and with no associated dust emission; (2) an almost unresolved UCH II region (EAST), located ~6" to the east of the cometary UCH II region, with an electron density ~1.3x10^5^/cm3, and associated with a compact dust clump detected at millimeter and mid-infrared wavelengths; and (3) a compact source (CORE), located ~2" to the southwest of the cometary arc, with a flux density increasing with frequency, and embedded in a dust condensation of 30M_{sun}_. The CORE source is resolved into two compact and unresolved sources which can be well fit by two homogeneous hypercompact H II regions each one photoionized by a B0.5 zero-age main sequence star, or by free-free radiation from shock-ionized gas resulting from the interaction of a jet/outflow system with the surrounding environment. The spatial distribution and kinematics of water masers close to the CORE-N and S sources, together with excess emission at 4.5{mu}m and the detected dust emission, suggest that the CORE source is a massive protostar driving a jet/outflow.
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- ID:
- ivo://CDS.VizieR/J/ApJ/707/1
- Title:
- Water and Methanol masers in NGC 6334I(N)
- Short Name:
- J/ApJ/707/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution, multi-wavelength study of the massive protostellar cluster NGC 6334 I(N) that combines new spectral line data from the Submillimeter Array (SMA) and VLA with a re-analysis of archival VLA continuum data, Two Micron All Sky Survey and Spitzer images. As shown previously, the brightest 1.3mm source SMA1 contains substructure at subarcsecond resolution, and we report the first detection of SMA1b at 3.6cm along with a new spatial component at 7mm (SMA1d). We find SMA1 (aggregate of sources a, b, c, and d) and SMA4 to be comprised of free-free and dust components, while SMA6 shows only dust emission. Our 1.5" resolution 1.3mm molecular line images reveal substantial hot-core line emission toward SMA1 and to a lesser degree SMA2. We find CH_3_OH rotation temperatures of 165+/-9K and 145+/-12K for SMA1 and SMA2, respectively. We estimate a diameter of 1400AU for the SMA1 hot-core emission, encompassing both SMA1b and SMA1d, and speculate that these sources comprise a >~800AU separation binary that may explain the previously suggested precession of the outflow emanating from the SMA1 region. Compact line emission from SMA4 is weak, and none is seen toward SMA6. The LSR velocities of SMA1, SMA2, and SMA4 all differ by 1-2km/s. Outflow activity from SMA1, SMA2, SMA4, and SMA6 is observed in several molecules including SiO(5-4) and IRAC 4.5um emission; 24um emission from SMA4 is also detected. Eleven water maser groups are detected, eight of which coincide with SMA1, SMA2, SMA4, and SMA6, while two others are associated with the Sandell source SM2. We also detect a total of 83 Class I CH_3_OH 44GHz maser spots which likely result from the combined activity of many outflows. Our observations paint the portrait of multiple young hot cores in a protocluster prior to the stage where its members become visible in the near-infrared.
- ID:
- ivo://CDS.VizieR/J/ApJ/764/61
- Title:
- Water maser and NH_3_ survey of GLIMPSE EGOs
- Short Name:
- J/ApJ/764/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a Nobeyama 45m H_2_O maser and NH_3_ survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5{mu}m emission. We observed the NH_3_(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms~50mK). The H_2_O maser detection rate is 68% (median rms~0.11Jy). The derived H_2_O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H_2_O masers and warm dense gas, as indicated by emission in the higher-excitation NH_3_ transitions, are most frequently detected toward EGOs also associated with both Class I and II CH_3_OH masers. Ninety-five percent (81%) of such EGOs are detected in H_2_O (NH_3_(3,3)), compared to only 33% (7%) of EGOs without either CH_3_OH maser type. As populations, EGOs associated with Class I and/or II CH_3_OH masers have significantly higher NH_3_ line widths, column densities, and kinetic temperatures than EGOs undetected in CH_3_OH maser surveys. However, we find no evidence for statistically significant differences in H_2_O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H_2_O maser luminosity and clump number density. H_2_O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/48
- Title:
- Water maser in Orion-KL with Herschel
- Short Name:
- J/ApJ/769/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have performed mapping observations of the 620.701GHz 5_32_-4_41_ transition of ortho-H_2_O within a ~1.5'x1.5' region encompassing the Kleinmann-Low nebula in Orion (Orion-KL), and pointed observations of that transition toward the Orion South condensation and the W49N region of high-mass star formation. Using the Effelsberg 100m radio telescope, we obtained ancillary observations of the 22.23508GHz 6_16_-5_23_ water maser transition; in the case of Orion-KL, the 621GHz and 22GHz observations were carried out within 10days of each other. The 621GHz water line emission shows clear evidence for strong maser amplification in all three sources, exhibiting narrow (~1km/s FWHM) emission features that are coincident (kinematically and/or spatially) with observed 22GHz features. Moreover, in the case of W49N --for which observations were available at three epochs spanning a 2yr period-- the spectra exhibited variability. The observed 621GHz/22GHz line ratios are consistent with a maser pumping model in which the population inversions arise from the combined effects of collisional excitation and spontaneous radiative decay, and the inferred physical conditions can plausibly arise in gas heated by either dissociative or non-dissociative shocks. The collisional excitation model also predicts that the 22GHz population inversion will be quenched at higher densities than that of the 621GHz transition, providing a natural explanation for the observational fact that 22GHz maser emission appears to be a necessary but insufficient condition for 621GHz maser emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/826/24
- Title:
- Water masers in M31. I. Recombination lines
- Short Name:
- J/ApJ/826/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a Green Bank Telescope survey for water masers, ammonia (1,1) and (2,2), and the H66{alpha} recombination line toward 506 luminous compact 24{mu}m emitting regions in the Andromeda Galaxy (M31). We include the 206 sources observed in the Darling water maser survey for completeness. The survey was sensitive enough to detect any maser useful for ~10{mu}as/yr astrometry. No new water masers, ammonia lines, or H66{alpha} recombination lines were detected individually or in spectral stacks reaching rms noise levels of ~3mJy and ~0.2mJy, respectively, in 3.1-3.3km/s channels. The lack of detections in individual spectra and in the spectral stacks is consistent with Galactic extrapolations. Contrary to previous assertions, there do not seem to be any additional bright water masers to be found in M31. The strong variability of water masers may enable new maser detections in the future, but variability may also limit the astrometric utility of known (or future) masers because flaring masers must also fade.
- ID:
- ivo://archive.stsci.edu/wuppe
- Title:
- Wisconsin Ultraviolet Photo-Polarimeter Experiment
- Short Name:
- WUPPE
- Date:
- 22 Jul 2020 21:33:04
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) was the spectropolarimetry component of the three ASTRO instruments that flew on Space Shuttle missions in December 1990 and March 1995. A halfwave spectropolarimeter provided medium resolution spectropolarimetry for research into the interstellar medium, hot stars, stars with circumstellar material, interacting binary stars, novae, solar system objects, and active galaxies. A Lyot analyzer obtained low resolution observations of faint targets, but due to calibration problems did not produce scientifically useful data. The WUPPE instrument provides a unique data set, one of the few providing polarimetric data in the ultraviolet portion of the spectrum.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A44
- Title:
- W51 Main NH_3_ and CH_3_OH data cubes
- Short Name:
- J/A+A/589/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is the third in a series of NH_3_ multilevel imaging studies in well-known, high-mass star-forming regions. The main goal is to characterize kinematics and physical conditions of (hot and dense) circumstellar molecular gas around O-type young stars. We want to map at subarcsecond resolution highly excited inversion lines of NH_3_ in the high-mass star-forming region W51 Main (distance = 5.4kpc), which is an ideal target to constrain theoretical models of high-mass star formation. Using the Karl Jansky Very Large Array (JVLA), we mapped the hot and dense molecular gas in W51 Main with ~0.2"-0.3" angular resolution in five metastable (J = K) inversion transitions of ammonia (NH_3_): (J,K) = (6, 6), (7, 7), (9, 9), (10, 10), and (13, 13). These lines arise from energy levels between ~400K and ~1700K above the ground state. We also made maps of the (free-free) continuum emission at frequencies between 25 and 36GHz.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/92
- Title:
- XMM survey of soft background. III. Galactic halo
- Short Name:
- J/ApJ/773/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on ~4/5 of our sight lines. The temperature is fairly uniform (median = 2.22x10^6^K, interquartile range = 0.63x10^6^K), while the emission measure and intrinsic 0.5-2.0keV surface brightness vary by over an order of magnitude (~(0.4-7)x10^-3^cm^-6^pc and ~(0.5-7)x10^-12^erg/cm2/s deg^-2^, respectively, with median detections of 1.9x10^-3^cm^-6^pc and 1.5x10^-12^erg/cm2/s deg^-2^, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/34
- Title:
- X-ray spectral analysis of 107 MW sight lines
- Short Name:
- J/ApJ/862/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation mechanism of the hot gaseous halo associated with the Milky Way is still under debate. We report new observational constraints on the gaseous halo using 107 lines of sight of the Suzaku X-ray observations at 75{deg}<l<285{deg} and |b|>15{deg} with a total exposure of 6.4Ms. The gaseous halo spectra are represented by a single-temperature plasma model in collisional ionization equilibrium. The median temperature of the observed fields is 0.26keV (3.0x10^6^K) with a typical fluctuation of ~30%. The emission measure varies by an order of magnitude and marginally correlates with the Galactic latitude. Despite the large scatter of the data, the emission measure distribution is roughly reproduced by a disk-like density distribution with a scale length of ~7kpc, a scale height of ~2kpc, and a total mass of ~5x10^7^M_{sun}_. In addition, we found that a spherical hot gas with the {beta}-model profile hardly contributes to the observed X-rays but that its total mass might reach >~10^9^M_{sun}_. Combined with indirect evidence of an extended gaseous halo from other observations, the hot gaseous halo likely consists of a dense disk-like component and a rarefied spherical component; the X-ray emissions primarily come from the former, but the mass is dominated by the latter. The disk-like component likely originates from stellar feedback in the Galactic disk due to the low scale height and the large scatter of the emission measures. The median [O/Fe] of ~0.25 shows the contribution of the core-collapse supernovae and supports the stellar feedback origin.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A115
- Title:
- X-ray survey of NGC7000/IC5070
- Short Name:
- J/A+A/602/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first extensive X-ray study of the North-America and Pelican star-forming region (NGC7000/IC5070), with the aim of finding and characterizing the young population of this cloud. X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings) were reduced and source detection algorithm applied to each image. We complement the X-ray data with optical and near-IR data from the IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and Spitzer IR data. More than 700 X-ray sources are detected, the majority of which have an optical or NIR counterpart. This allowed us to identify young stars in different stages of formation. Less than 30% of X-ray sources are identified with a previously known young star. We argue that most X-ray sources with an optical or NIR counterpart, except perhaps for a few tens at near-zero reddening, are likely candidate members of the star-forming region, on the basis of both their optical and NIR magnitudes and colors, and of X-ray properties such as spectrum hardness or flux variations. They are characterized by a wide range of extinction, and sometimes near-IR excesses, both of which prevent derivation of accurate stellar parameters. The optical color-magnitude diagram suggests ages between 1-10Myrs. The X-ray members have a very complex spatial distribution with some degree of subclustering, qualitatively similar to that of previously known members. The detailed distribution of X-ray sources relative to the objects with IR excesses identified with Spitzer is sometimes suggestive of sequential star formation, especially near the 'Gulf of Mexico' region, probably triggered by the O5 star which illuminates the whole region. We confirm that around the O5 star no enhancement in the young star density is found, in agreement with previous results. Thanks to the precision and depth of the IPHAS and UKIDSS data used, we also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region.
