- ID:
- ivo://CDS.VizieR/J/A+A/566/A47
- Title:
- Milky Way nuclear star cluster extinction map
- Short Name:
- J/A+A/566/A47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although the Milky Way Nuclear Star Cluster (MWNSC) was discovered more than four decades ago, several of its key properties have not been determined unambiguously up to now because of the strong and spatially highly variable interstellar extinction toward the Galactic centre. In this paper we aim at determining the shape, size, and luminosity/mass of the MWNSC.In order to investigate the properties of the MWNSC, we use Spitzer/IRAC images at 3.6 and 4.5{mu}m, where interstellar extinction is at a minimum but the overall emission is still dominated by stars. We correct the 4.5{mu}m image for PAH emission with the help of the IRAC 8.0{mu}m map and for extinction with the help of a [3.6-4.5] colour map. Finally, we investigate the symmetry of the nuclear cluster and fit it with Sersic, Moffat, and King models. We present an extinction map for the central ~300x200pc^2^ of the Milky Way, as well as a PAH-emission and extinction corrected image of the stellar emission, with a resolution of about 0.20pc. We find that the MWNSC appears in projection intrinsically point-symmetric, that it is significantly flattened, with its major axis aligned along the Galactic Plane, and that it is centred on the black hole, Sagittarius A*. Its density follows the well known approximate {rho}{prop.to}r^-2^-law at distances of a few parsecs from Sagittarius A*, but becomes as steep as about {rho}{prop.to}r^-3^ at projected radii around 5pc. We derive a half light radius of 4.2+/-0.4pc, a total luminosity of L_MWNSC,4.5{mu}m_=4.1+/-0.4x10^7^L_{sun}_, and a mass of M_MWNSC_=2.1+/-0.4x10^7^M_{sun}_. The overall properties of the MWNSC agree well with the ones of its extragalactic counterparts, which underlines its role as a template for these objects. Its flattening agrees well with its previously established rotation parallel to Galactic rotation and suggests that it has formed by accretion of material that fell in preferentially along the Galactic Plane. Our findings support the in situ growth scenario for nuclear clusters and emphasize the need to increase the complexity of theoretical models for their formation and for the interaction between their stars and the central black hole in order to include rotation, axisymmetry, and growth in recurrent episodes.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/149/64
- Title:
- MIPSGAL 24{mu}m point source catalog
- Short Name:
- J/AJ/149/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this contribution, we describe the applied methods to construct a 24{mu}m based point source catalog derived from the image data of the MIPSGAL 24{mu}m Galactic Plane Survey and the corresponding data products. The high quality catalog product contains 933818 sources, with a total of 1353228 in the full archive catalog. The source tables include positional and photometric information derived from the 24{mu}m images, source quality and confusion flags, and counterpart photometry from matched 2MASS, GLIMPSE, and WISE point sources. Completeness decay data cubes are constructed at 1' angular resolution that describe the varying background levels over the MIPSGAL field and the ability to extract sources of a given magnitude from this background. The completeness decay cubes are included in the set of data products. We present the results of our efforts to verify the astrometric and photometric calibration of the catalog, and present several analyses of minor anomalies in these measurements to justify adopted mitigation strategies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/2222
- Title:
- 1.1mm dust continuum emission along Gal. plane
- Short Name:
- J/MNRAS/473/2222
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive, imaging observations of the {lambda}1.1mm dust continuum emission from a 1deg^2^ area collected with the AzTEC bolometer camera on the Large Millimeter Telescope are presented. A catalogue of 1545 compact sources is constructed based on a Wiener-optimization filter. These sources are linked to larger clump structures identified in the Bolocam Galactic Plane Survey. Hydrogen column densities are calculated for all sources and mass and mean volume densities are derived for the subset of sources for which kinematic distances can be assigned. The AzTEC sources are localized, high-density peaks within the massive clumps of molecular clouds and comprise 5-15 per cent of the clump mass. We examine the role of the gravitational instability in generating these fragments by comparing the mass of embedded AzTEC sources to the Jeans mass of the parent BGPS object. For sources with distances less than 6kpc the fragment masses are comparable to the clump Jeans mass, despite having isothermal Mach numbers between 1.6 and 7.2. AzTEC sources linked to ultra compact HII regions have mass surface densities greater than the critical value implied by the mass-size relationship of infrared dark clouds with high-mass star formation, while AzTEC sources associated with Class II methanol masers have mass surface densities greater than 0.7gcm^-2^ that approaches the proposed threshold required to form massive stars.
- 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.
- 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.
- 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.
- 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.
- 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).
- 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.
- 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.
