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381. M-3.8+0.9 molecular cloud 3mm datacubes
ID:
ivo://CDS.VizieR/J/A+A/613/A42
Title:
M-3.8+0.9 molecular cloud 3mm datacubes
Short Name:
J/A+A/613/A42
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to reveal the morphology, chemical composition, kinematics and to establish the main processes prevalent in the gas at the footpoints of the giant molecular loops (GMLs) in the Galactic center region. Using the 22-m Mopra telescope, we mapped the M-3.8+0.9 molecular cloud, placed at the footpoints of a giant molecular loop, in 3-mm range molecular lines. To derive the molecular hydrogen column density, we also observed the ^13^CO (2-1) line at 1mm using the 12-m APEX telescope. From the 3 mm observations 12 molecular species were detected, namely HCO+, HCN, H^13^CN, HNC, SiO, CS, CH_3_OH, N_2_H^+^, SO, HNCO, OCS, and HC_3_N. Maps revealing the morphology and kinematics of the M-3.8+0.9 molecular cloud in different molecules are presented. We identify six main molecular complexes. We derive fractional abundances in 11 selected positions of the different molecules assuming local thermodynamical equilibrium. Most of the fractional abundances derived for the M-3.8+0.9 molecular cloud are very similar over the whole cloud. However, the fractional abundances of some molecules show significant difference with respect to those measured in the central molecular zone (CMZ). The abundances of the shock tracer SiO are very similar between the GMLs and the CMZ. The methanol emission is the most abundant species in the GMLs. This indicates that the gas is likely affected by moderate ~30km/s or even high velocity (50km/s) shocks, consistent with the line profile observed toward one of the studied position. The origin of the shocks is likely related to the flow of the gas throughout the GMLs towards the footpoints.
382. MMT hypervelocity star survey. II.
ID:
ivo://CDS.VizieR/J/ApJ/751/55
Title:
MMT hypervelocity star survey. II.
Short Name:
J/ApJ/751/55
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of five new unbound hypervelocity stars (HVSs) in the outer Milky Way halo. Using a conservative estimate of Galactic escape velocity, our targeted spectroscopic survey has now identified 16 unbound HVSs as well as a comparable number of HVSs ejected on bound trajectories. A Galactic center origin for the HVSs is supported by their unbound velocities, the observed number of unbound stars, their stellar nature, their ejection time distribution, and their Galactic latitude and longitude distribution. Other proposed origins for the unbound HVSs, such as runaway ejections from the disk or dwarf galaxy tidal debris, cannot be reconciled with the observations. An intriguing result is the spatial anisotropy of HVSs on the sky, which possibly reflects an anisotropic potential in the central 10-100pc region of the Galaxy. Further progress requires measurement of the spatial distribution of HVSs over the southern sky. Our survey also identifies seven B supergiants associated with known star-forming galaxies; the absence of B supergiants elsewhere in the survey implies there are no new star-forming galaxies in our survey footprint to a depth of 1-2Mpc.
383. Mn abundances of Galactic disc stars
ID:
ivo://CDS.VizieR/J/MNRAS/454/1585
Title:
Mn abundances of Galactic disc stars
Short Name:
J/MNRAS/454/1585
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we present and discuss the observations of the Mn abundances for 247 FGK dwarfs, located in the Galactic disc with metallicity -1<[Fe/H]<+0.3. The observed stars belong to the substructures of the Galaxy thick and thin disks, and to the Hercules stream. The observations were conducted using the 1.93m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle-type spectrographs ELODIE and SOPHIE. The abundances were derived under the LTE approximation, with an average error for the [Mn/Fe] ratio of 0.10dex. For most of the stars in the sample, Mn abundances are not available in the literature. We obtain an evolution of [Mn/Fe] ratio with the metallicity [Fe/H] consistent with previous data compilations. In particular, within the metallicity range covered by our stellar sample, the [Mn/Fe] ratio is increasing with the increase of metallicity. This due to the contribution to the Galactic chemical evolution of Mn and Fe from thermonuclear supernovae. We confirm the baseline scenario where most of the Mn in the Galactic disc and in the Sun is made by thermonuclear supernovae. In particular, the effective contribution from core-collapse supernovae to the Mn in the Solar system is about 10-20 per cent. However, present uncertainties affecting the production of Mn and Fe in thermonuclear supernovae are limiting the constraining power of the observed [Mn/Fe] trend in the Galactic discs on, e.g. the frequency of different thermonuclear supernovae populations. The different production of these two elements in different types of thermonuclear supernovae needs to be disentangled by the dependence of their relative production on the metallicity of the supernova progenitor.
384. Molecular cloud assoc. to Milky Way spiral arms
ID:
ivo://CDS.VizieR/J/A+A/658/A54
Title:
Molecular cloud assoc. to Milky Way spiral arms
Short Name:
J/A+A/658/A54
Date:
22 Feb 2022
Publisher:
CDS
Description:
The morphology of the Milky Way is still a matter of debate. In order to shed light on the uncertainty surrounding the Galactic structure, in this paper, we study the imprint of spiral arms on the molecular gas distribution and properties. To do so, we take full advantage of the SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium) survey that observed a large area of the inner Galaxy in the ^13^CO(2-1) line at an angular resolution of 28". We analyse the influences of spiral arms by considering the features of the molecular gas emission as a whole across the longitude- velocity map built from the full survey. Additionally, we examine the properties of the molecular clouds in the spiral arms compared to those in the inter-arm regions. Through flux and luminosity probability distribution functions, we find that the molecular gas emission associated with the spiral arms does not differ much from the emission between the arms. On average, spiral arms show masses per unit length of ~10^5^-10^6^M_{sun}_/kpc. This is similar to values inferred from data sets in which emission distributions were segmented into molecular clouds. By examining the cloud distribution across the Galactic plane, we infer that the molecular mass in the spiral arms is a factor of 1.5 higher than that of the inter-arm medium, similar to what is found for other spiral galaxies in the local Universe. We observe that only the distributions of cloud mass surface densities and aspect ratio in the spiral arms show significant differences compared to those of the inter-arm medium; other observed differences appear instead to be driven by a distance bias. By comparing our results with simulations and observations of nearby galaxies, we conclude that the measured quantities would classify the Milky Way as a flocculent spiral galaxy, rather than as a grand-design one.
385. Molecular clouds and star formation
ID:
ivo://CDS.VizieR/J/A+A/588/A104
Title:
Molecular clouds and star formation
Short Name:
J/A+A/588/A104
Date:
21 Oct 2021
Publisher:
CDS
Description:
As a part of the Milky Way Imaging Scroll Painting (MWISP) survey, the aim is to study the physical properties of molecular clouds and their associated star formation toward the Galactic plane within 216.25{deg}<=l<=218.75{deg} and -0.75{deg}<=b<=1.25{deg}, which covers the molecular cloud complex S287. Using the 3x3 Superconducting Spectroscopic Array Receiver (SSAR) at the PMO-13.7m telescope, we performed a simultaneous ^12^CO (1-0), ^13^CO (1-0), C^18^O (1-0) mapping toward molecular clouds in a region encompassing 3.75 square degrees. The beam size is 52" for ^12^CO (1-0) and 55" for ^13^CO (1-0) and C^18^O (1-0).
386. Molecular clouds in the Milky Way with CO obs.
ID:
ivo://CDS.VizieR/J/ApJ/828/59
Title:
Molecular clouds in the Milky Way with CO obs.
Short Name:
J/ApJ/828/59
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Galactic plane has been mapped from l=34.75{deg} to 45.25{deg} and b=-5.25{deg} to 5.25{deg} in the CO (J=1-0) emission with the 13.7m telescope of the Purple Mountain Observatory. The unbiased survey covers a large area of 110 square degrees sampled every 30" with a velocity resolution of ~0.2km/s. In this paper, we present the result of an unbiased CO survey of this longitude and latitude range in the velocity range from -60 to -10km/s. Over 500 molecular clouds (MCs) are picked out from the ^12^CO (J=1-0) emission, and 131 of these MCs are associated with ^13^CO emission. The distant MCs, which lie beyond the solar circle and are mostly concentrated in the Galactic plane, trace the large-scale molecular gas structure over 10 degrees of Galactic azimuth. We find that the distribution of the distant MCs can be well fitted by a Gaussian function with a full width at half maximum (FWHM) of 0.7{deg} with the Galactic latitude. We suggest that the CO emission of the segment is from the Outer Arm. The physical mid-plane traced by the Outer Arm seems to be slightly displaced from the IAU-defined plane on a large scale, which could be explained by the warped plane at large Galactocentric distances of >~10kpc and the apparent tilted mid-plane to the projected IAU-defined plane caused by the Sun's z-height above the disk for distances near and within the Solar circle. After removing the effect of the warp and tilted structure, the scale height of the MCs in the Outer Arm is about 0.6{deg} or 160pc at a heliocentric distance of 15kpc. If the inner plane of our Galaxy is flat, we can derive an upper limit of the Sun's offset of ~17.1pc above the physical mid-plane of the Milky Way. We also discuss the correlations between the physical parameters of the distant MCs, which is quite consistent with the result of other studies of this parameter.
387. Monoceros Overdensity deep imaging with Subaru
ID:
ivo://CDS.VizieR/J/ApJ/754/101
Title:
Monoceros Overdensity deep imaging with Subaru
Short Name:
J/ApJ/754/101
Date:
21 Oct 2021
Publisher:
CDS
Description:
We derive distance, density, and metallicity distribution of the stellar Monoceros Overdensity (MO) in the outer Milky Way, based on deep imaging with the Subaru Telescope. We applied color-magnitude diagram fitting techniques in three stripes at galactic longitudes, l~130{deg}, 150{deg}, 170{deg}, and galactic latitudes, +15{deg}<=b<=+25{deg}. The MO appears as a wall of stars at a heliocentric distance of ~10.1+/-0.5kpc across the observed longitude range with no distance change. The MO stars are more metal-rich ([Fe/H]~-1.0) than the nearby stars at the same latitude. These data are used to test three different models for the origin of the MO: a perturbed disk model, which predicts a significant drop in density adjacent to the MO that is not seen; a basic flared disk model, which can give a good match to the density profile but the MO metallicity implies the disk is too metal-rich to source the MO stars; and a tidal stream model, which, from the literature, brackets the distances and densities we derive for the MO, suggesting that a model can be found that would fully fit the MO data. Further data and modeling will be required to confirm or rule out the MO feature as a stream or as a flaring of the disk.
388. Morphology of candidate intermediate-mass SFRs
ID:
ivo://CDS.VizieR/J/ApJ/784/111
Title:
Morphology of candidate intermediate-mass SFRs
Short Name:
J/ApJ/784/111
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an all-sky sample of 984 candidate intermediate-mass Galactic star-forming regions that are color selected from the Infrared Astronomical Satellite (IRAS) Point Source Catalog and morphologically classify each object using mid-infrared Wide-field Infrared Survey Explorer (WISE) images. Of the 984 candidates, 616 are probable star-forming regions (62.6%), 128 are filamentary structures (13.0%), 39 are point-like objects of unknown nature (4.0%), and 201 are galaxies (20.4%). We conduct a study of four of these regions, IRAS 00259+5625, IRAS 00420+5530, IRAS 01080+5717, and IRAS 05380+2020, at Galactic latitudes|b|>5{deg} using optical spectroscopy from the Wyoming Infrared Observatory, along with near-infrared photometry from the Two-Micron All Sky Survey, to investigate their stellar content. New optical spectra, color-magnitude diagrams, and color-color diagrams reveal their extinctions, spectrophotometric distances, and the presence of small stellar clusters containing 20-78M_{sun}_ of stars. These low-mass diffuse star clusters contain ~65-250 stars for a typical initial mass function, including one or more mid-B stars as their most massive constituents. Using infrared spectral energy distributions we identify young stellar objects near each region and assign probable masses and evolutionary stages to the protostars. The total infrared luminosity lies in the range 190-960L_{sun}_, consistent with the sum of the luminosities of the individually identified young stellar objects.
389. MSX high-contrast IRDCs with NH_3_
ID:
ivo://CDS.VizieR/J/A+A/552/A40
Title:
MSX high-contrast IRDCs with NH_3_
Short Name:
J/A+A/552/A40
Date:
21 Oct 2021
Publisher:
CDS
Description:
Despite increasing research in massive star formation, little is known about its earliest stages. Infrared Dark Clouds (IRDCs) are cold, dense and massive enough to harbour the sites of future high-mass star formation. But up to now, mainly small samples have been observed and analysed. To understand the physical conditions during the early stages of high-mass star formation, it is necessary to learn more about the physical conditions and stability in relatively unevolved IRDCs. Thus, for characterising IRDCs studies of large samples are needed. We investigate a complete sample of 220 northern hemisphere high-contrast IRDCs using the ammonia (1,1)- and (2,2)-inversion transitions. We detected ammonia (1,1)-inversion transition lines in 109 of our IRDC candidates. Using the data we were able to study the physical conditions within the star-forming regions statistically. We compared them with the conditions in more evolved regions which have been observed in the same fashion as our sample sources. Our results show that IRDCs have, on average, rotation temperatures of 15K, are turbulent (with line width FWHMs around 2km/s), have ammonia column densities on the order of 10^14^cm^-2^ and molecular hydrogen column densities on the order of 10^22^cm^-2^. Their virial masses are between 100 and a few 1000M_{sun}_. The comparison of bulk kinetic and potential energies indicate that the sources are close to virial equilibrium. IRDCs are on average cooler and less turbulent than a comparison sample of high-mass protostellar objects, and have lower ammonia column densities. Virial parameters indicate that the majority of IRDCs are currently stable, but are expected to collapse in the future.
390. Multiwavelength study of Sgr A*
ID:
ivo://CDS.VizieR/J/A+A/589/A116
Title:
Multiwavelength study of Sgr A*
Short Name:
J/A+A/589/A116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of the multiwavelength study of the flaring activity of the supermassive black hole named Sgr A* is located at the dynamical center of the Milky Way. We detected two X-ray flares on 2014 Mar. 10 and Apr. 2 with XMM-Newton, three near-infrared (NIR) flares with HST on 2014 Mar. 10 and Apr. 2, and two NIR flares on 2014 Apr. 3 and 4 with VLT. The X-ray flare on 2014 Mar. 10 is characterized by a long rise and a rapid decay. Its total duration is one of the longest detected so far in X-rays. Its NIR counterpart peaked well before the X-ray maximum, implying a dramatic change in the X-ray-to-NIR flux ratio during this event. This NIR/X-ray flare is interpreted as either a single flare where variation in the X-ray-to-NIR flux ratio is explained by the adiabatic compression of a plasmon, or two distinct flaring components separated by 1.2h with simultaneous peaks in X-rays and NIR. We identified an increase in the rising radio flux density at 13.37GHz on 2014 Mar. 10 with the VLA that could be the delayed radio emission from a NIR/X-ray flare that occurred before the start of our observation. The X-ray flare on 2014 Apr. 2 occurred for HST during the occultation of Sgr A* by the Earth, therefore we only observed the start of its NIR counterpart. With NIR synchrotron emission from accelerated electrons and assuming X-rays from synchrotron self-Compton emission, the region of this NIR/X-ray flare has a size of 0.03-7 times the Schwarzschild radius and an electron density of 10^8.5-10^10.2cm^-3^, assuming a synchrotron spectral index of 0.3-1.5. When Sgr A* reappeared to the HST view, we observed the decay phase of a distinct bright NIR flare with no detectable counterpart in X-rays. On 2014 Apr. 3, two 95GHz flares were observed with CARMA, where the first may be the delayed emission of a NIR flare observed with VLT.