Search

Start Over Subject milky way galaxy Validation Level 2
211. Galactic interstellar dust Gaia-2MASS 3D maps
ID:
ivo://CDS.VizieR/J/A+A/625/A135
Title:
Galactic interstellar dust Gaia-2MASS 3D maps
Short Name:
J/A+A/625/A135
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gaia stellar measurements are currently revolutionizing our knowledge of the evolutionary history of the Milky Way. 3D maps of the interstellar dust provide complementary information and are a tool for a wide range of uses. We built 3D maps of the dust in the Local arm and surrounding regions. To do so, Gaia DR2 photometric data were combined with 2MASS measurements to derive extinction toward stars that possess accurate photometry and relative uncertainties on DR2 parallaxes smaller than 20%. We applied a new hierarchical inversion algorithm to the individual extinctions that is adapted to large datasets and to an inhomogeneous target distribution. Each step associates regularized Bayesian inversions in all radial directions and a subsequent inversion in 3D of all their results. Each inverted distribution serves as a prior for the subsequent step, and the spatial resolution is progressively increased. We present the resulting 3D distribution of the dust in a 6x6x0.8kpc^3^ volume around the Sun. Its main features are found to be elongated along different directions that vary from below to above the mid-plane. The outer part of Carina-Sagittarius, mainly located above the mid-plane, the Local arm/Cygnus Rift around and above the mid-plane, and the fragmented Perseus arm are oriented close to the direction of circular motion. The spur of more than 2kpc length (nicknamed the split) that extends between the Local Arm and Carina-Sagittarius, the compact near side of Carina-Sagittarius, and the Cygnus Rift below the Plane are oriented along l~40 to 55{deg}. Dust density images in vertical planes reveal a wavy pattern in some regions and show that the solar neighborhood within 500 pc remains atypical by its extent above and below the Plane. We show several comparisons with the locations of molecular clouds, HII regions, O stars, and masers. The link between the dust concentration and these tracers is markedly different from one region to the other
212. Galactic interstellar ratio ^18^O/^17^O. I.
ID:
ivo://CDS.VizieR/J/ApJS/249/6
Title:
Galactic interstellar ratio ^18^O/^17^O. I.
Short Name:
J/ApJS/249/6
Date:
21 Oct 2021
Publisher:
CDS
Description:
The interstellar oxygen isotopic ratio of ^18^O/^17^O can reflect the relative amount of the secular enrichment by ejecta from high-mass versus intermediate-mass stars. Previous observations found a Galactic gradient of ^18^O/^17^O, i.e., low ratios in the Galactic center and large values in the Galactic disk, which supports the inside-out formation scenario of our Galaxy. However, there are not many observed objects and, in particular, there are not many at large galactocentric distances. For this reason, we started a systematic study on Galactic interstellar ^18^O/^17^O, through observations of C^18^O and C^17^O multi-transition lines toward a large sample of 286 sources (at least one order of magnitude larger than previous ones), from the Galactic center region to the far outer Galaxy (~22kpc). In this article, we present our observations of J=1-0 lines of C^18^O and C^17^O, with the 12m antenna of the Arizona Radio Observatory (ARO 12m) and the Institut de Radio Astronomie Millimetrique (IRAM) 30m telescopes. Among our IRAM 30m sample of 50 targets, we detected successfully both C^18^O and C^17^O 1-0 lines for 34 sources. Similarly, our sample of 260 targets for ARO 12m observations resulted in the detection of both lines for 166 sources. The C^18^O optical depth effect on our ratio results, evaluated by fitting results of C^17^O spectra with hyperfine components (assuming {tau}_C18O_=4{tau}_C17O_) and our radiative transfer and excitation model nonlocal thermodynamic equilibrium (non-LTE) model calculation for the strongest source, was found to be insignificant. Beam dilution does not seem to be a problem either, which was supported by the fact that there is no systematic variation between the isotopic ratio and the heliocentric distance, and ratios are consistently measured from two telescopes for most of those detected sources. With this study we obtained ^18^O/^17^O isotopic ratios for a large sample of molecular clouds with different galactocentric distances. Our results, though there are still very few detections made for sources in the outer Galaxy, confirm the apparent ^18^O/^17^O gradient of ^18^O/^17^O=(0.10+/-0.03)R_GC_+(2.95+/-0.30), with a Pearson's rank correlation coefficient of R=0.69. This is supported by the newest Galactic chemical evolution model including the impact of massive stellar rotators and novae.
213. Galactic kinematics from YSOs sample
ID:
ivo://CDS.VizieR/J/PAZh/39/601
Title:
Galactic kinematics from YSOs sample
Short Name:
J/PAZh/39/601
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on published sources, we have created a kinematic database on 220 massive (>10M_{sun}_) young Galactic star systems located within <3 kpcof the Sun. Out of them, approximately 100 objects are spectroscopic binary and multiple star systems whose components are massive OB stars; the remaining objects are massive Hipparcos B stars with parallax errors of no more than 10 percent. Based on the entire sample, we have constructed the Galactic rotation curve, determined the circular rotation velocity of the solar neighborhood around the Galactic center R_0_=8kpc, V_0_=259+/-16km/s, and obtained the following spiral density wave parameters: the amplitudes of the radial and azimuthal velocity perturbations f_R_=-10.8+/-1.2km/s, and f_{theta}_=7.9+/-1.3km/s, respectively; the pitch angle for a two-armed spiral pattern i=-6.0+/-0.4deg, with the wavelength of the spiral density wave near the Sun being {lambda}=2.6+/-0.2kpc; and the radial phase of the Sun in the spiral density wave {chi}_{sun}_=-120+/-4{deg}. We show that such peculiarities of the Gould Belt as the local expansion of the system, the velocity ellipsoid vertex deviation, and the significant additional rotation can be explained in terms of the density wave theory. All these effects decrease noticeably once the influence of the spiral density wave on the velocities of nearby stars has been taken into account. The influence of Gould Belt stars on the Galactic parameter estimates has also been revealed. Eliminating them from the kinematic equations has led to the following new values of the spiral density wave parameters: f_{theta}_=2.9+/-2.1km/s and {chi}_{sun}_=-104+/-6{deg}.
214. Galactic MCs associated with HII regions
ID:
ivo://CDS.VizieR/J/ApJ/831/73
Title:
Galactic MCs associated with HII regions
Short Name:
J/ApJ/831/73
Date:
21 Oct 2021
Publisher:
CDS
Description:
The relations between star formation and properties of molecular clouds (MCs) are studied based on a sample of star-forming regions in the Galactic Plane. Sources were selected by having radio recombination lines to provide identification of associated MCs and dense clumps. Radio continuum emission and mid-infrared emission were used to determine star formation rates (SFRs), while ^13^CO and submillimeter dust continuum emission were used to obtain the masses of molecular and dense gas, respectively. We test whether total molecular gas or dense gas provides the best predictor of SFR. We also test two specific theoretical models, one relying on the molecular mass divided by the free-fall time, the other using the free-fall time divided by the crossing time. Neither is supported by the data. The data are also compared to those from nearby star-forming regions and extragalactic data. The star formation "efficiency," defined as SFR divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all of the molecular gas.
215. Galactic midplane Spitzer red sources
ID:
ivo://CDS.VizieR/J/AJ/136/2413
Title:
Galactic midplane Spitzer red sources
Short Name:
J/AJ/136/2413
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a highly reliable flux-limited census of 18949 point sources in the Galactic midplane that have intrinsically red mid-infrared colors. These sources were selected from the Spitzer Space Telescope Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE) I and II surveys of 274{deg}^2^ of the Galactic midplane, and consist mostly of high- and intermediate-mass young stellar objects (YSOs) and asymptotic giant branch (AGB) stars. The selection criteria were carefully chosen to minimize the effects of position-dependent sensitivity, saturation, and confusion. The distribution of sources on the sky and their location in the Infrared Array Camera and the Multiband Image Photometer for Spitzer 24um color-magnitude and color-color space are presented. Using this large sample, we find that YSOs and AGB stars can be mostly separated by simple color-magnitude selection criteria into approximately 50%-70% of YSOs and 30%-50% of AGB stars. Planetary nebulae and background galaxies together represent at most 2%-3% of all the red sources. 1004 red sources in the GLIMPSE II region, mostly AGB stars with high mass-loss rates, show significant (>=0.3mag) variability at 4.5 and/or 8.0um. With over 11,000 likely YSOs and over 7000 likely AGB stars, this is to date the largest uniform census of AGB stars and high- and intermediate-mass YSOs in the Milky Way Galaxy.
216. Galactic novae with m<=10 from 1900 to 2015
ID:
ivo://CDS.VizieR/J/ApJ/834/196
Title:
Galactic novae with m<=10 from 1900 to 2015
Short Name:
J/ApJ/834/196
Date:
21 Oct 2021
Publisher:
CDS
Description:
Despite its fundamental importance, a reliable estimate of the Galactic nova rate has remained elusive. Here, the overall Galactic nova rate is estimated by extrapolating the observed rate for novae reaching m<=2 to include the entire Galaxy using a two component disk plus bulge model for the distribution of stars in the Milky Way. The present analysis improves on previous work by considering important corrections for incompleteness in the observed rate of bright novae and by employing a Monte Carlo analysis to better estimate the uncertainty in the derived nova rates. Several models are considered to account for differences in the assumed properties of bulge and disk nova populations and in the absolute magnitude distribution. The simplest models, which assume uniform properties between bulge and disk novae, predict Galactic nova rates of ~50 to in excess of 100 per year, depending on the assumed incompleteness at bright magnitudes. Models where the disk novae are assumed to be more luminous than bulge novae are explored, and predict nova rates up to 30% lower, in the range of ~35 to ~75 per year. An average of the most plausible models yields a rate of 50_-23_^+31^yr^-1^, which is arguably the best estimate currently available for the nova rate in the Galaxy. Virtually all models produce rates that represent significant increases over recent estimates, and bring the Galactic nova rate into better agreement with that expected based on comparison with the latest results from extragalactic surveys.
217. GALACTICNUCLEUS IV. JHKs imaging survey
ID:
ivo://CDS.VizieR/J/A+A/653/A133
Title:
GALACTICNUCLEUS IV. JHKs imaging survey
Short Name:
J/A+A/653/A133
Date:
10 Mar 2022 11:26:04
Publisher:
CDS
Description:
The extreme extinction (A_V_~30mag) and its variation on arc-second scales towards the Galactic centre hamper the study of its stars. Their analysis is restricted to the near infrared (NIR) regime, where the extinction curve can be approximated by a broken power law for the JHKs bands. Therefore, correcting for extinction at these wavelengths is fundamental to analyse the structure and stellar population of the central regions of our Galaxy. We aim at: (1) Discussing different strategies to de-redden the photometry and checking the usefulness of extinction maps to deal with variable stars. (2) Building and making publicly available extinction maps for the NIR bands JHKs. (3) Creating a de-reddened catalogue of the GALACTICNUCLEUS (GNS) survey, identifying foreground stars. (4) Performing a preliminary analysis of the de-reddened $K_s$ luminosity functions (KLFs). We use photometry from the GNS survey to create extinction maps for the whole catalogue. We take red clump (RC) and red giant stars of similar brightness as a reference to build the maps, and de-redden the GNS photometry. We discuss the limitations of the process and analyse non-linear effects of the de-reddening. We create high resolution (~3'') extinction maps with low statistical and systematics uncertainties (<~5%), and compute average extinctions for each of the regions covered by the GNS. We check that our maps effectively correct the differential extinction reducing the spread of the RC features by a factor of ~2. We assess the validity of the broken power law approach computing two equivalent extinction maps A_H_ using either JH and HKs photometry for the same reference stars, and obtain compatible average extinctions within the uncertainties. Finally, we analyse de-reddened KLFs for different line-of-sights and find that the regions belonging to the NSD contain a homogeneous stellar population that is significantly different from the one in the innermost bulge regions.
218. GALACTICNUCLEUS: JHKs imaging survey
ID:
ivo://CDS.VizieR/J/A+A/610/A83
Title:
GALACTICNUCLEUS: JHKs imaging survey
Short Name:
J/A+A/610/A83
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Galactic Centre is of fundamental astrophysical interest, but existing near-infrared surveys fall short covering it adequately, either in terms of angular resolution, multi-wavelength coverage, or both. Here we introduce the GALACTICNUCLEUS survey, a JHKs imaging survey of the centre of the Milky Way with a 0.2" angular resolution. The purpose of this paper is to present the observations of Field 1 of our survey, centred approximately on SgrA* with an approximate size of 7.95'x3.43'. We describe the observational set-up and data reduction pipeline and discuss the quality of the data. Finally, we present the analysis of the data. The data were acquired with the near-infrared camera HAWK-I (High Acuity Wide field K-band Imager) at the ESO VLT (Very Large Telescope). Short readout times in combination with the speckle holography algorithm allowed us to produce final images with a stable, Gaussian PSF (point spread function) of 0.2" FWHM (full width at half maximum). Astrometric calibration is achieved via the VVV (VISTA Variables in the Via Lactea) survey and photometric calibration is based on the SIRIUS/IRSF (Infrared Survey Facility telescope) survey. The quality of the data is assessed by comparison between observations of the same field with different detectors of HAWK-I and at different times. We reach 5{sigma} uncertainties are less than 0.05" at J<=20, H<=17, and Ks<=16. We can distinguish five stellar populations in the colour-magnitude diagrams; three of them appear to belong to foreground spiral arms, and the other two correspond to high- and low-extinction star groups at the Galactic Centre. We use our data to analyse the near-infrared extinction curve and find some evidence for a possible difference between the extinction index between J-H and H-Ks. However, we conclude that it can be described very well by a power law with an index of JHKs=2.30+.-0.08. We do not find any evidence that this index depends on the position along the line of sight, or on the absolute value of the extinction. We produce extinction maps that show the clumpiness of the ISM (interstellar medium) at the Galactic Centre. Finally, we estimate that the majority of the stars have solar or super-solar metallicity by comparing our extinction-corrected colour-magnitude diagrams with isochrones with different metallicities and a synthetic stellar model with a constant star formation.
219. GALACTICNUCLEUS JHKs imaging survey. II.
ID:
ivo://CDS.VizieR/J/A+A/631/A20
Title:
GALACTICNUCLEUS JHKs imaging survey. II.
Short Name:
J/A+A/631/A20
Date:
21 Oct 2021
Publisher:
CDS
Description:
The high extinction and extreme source crowding of the central regions of the Milky Way are serious obstacles to the study of the structure and stellar population of the Galactic centre (GC). Surveys that cover the GC region (2MASS, UKIDSS, VVV, SIRIUS) do not have the necessary high angular resolution. Therefore, a high angular resolution survey in the near infrared is crucial to improve the state of the art. Here, we present the GALACTICNUCLEUS catalogue, a near infrared JHKs high angular resolution (0.2") survey of the nuclear bulge of the Milky Way. We explain in detail the data reduction, data analysis, calibration, and uncertainty estimation of the GALACTICNUCLEUS survey. We assess the data quality comparing our results with previous surveys. We obtained accurate JHKs photometry ~3.3x10^6^ stars in the GC detecting around 20% in J, 65% in H and 90% in Ks. The survey covers a total area of ~0.3 square degrees, which corresponds to ~6000pc^2^. The GALACTICNUCLEUS survey reaches 5 sigma detections for J~22mag, H~21mag and Ks~21mag. The uncertainties are below 0.05mag at J~21mag, H~19mag and Ks~18mag. The zero point systematic uncertainty is <~0.04mag in all three bands. We present colour-magnitude diagrams for the different regions covered by the survey.
220. Galactic outer disk: a field toward Tombaugh 1
ID:
ivo://CDS.VizieR/J/AJ/153/99
Title:
Galactic outer disk: a field toward Tombaugh 1
Short Name:
J/AJ/153/99
Date:
21 Oct 2021
Publisher:
CDS
Description:
We employ optical photometry and high-resolution spectroscopy to study a field toward the open cluster Tombaugh 1, where we identify a complex population mixture that we describe in terms of young and old Galactic thin disks. Of particular interest is the spatial distribution of the young population, which consists of dwarfs with spectral types as early as B6 and is distributed in a blue plume feature in the color-magnitude diagram. For the first time, we confirm spectroscopically that most of these stars are early-type stars and not blue stragglers or halo/thick-disk subdwarfs. Moreover, they are not evenly distributed along the line of sight but crowd at heliocentric distances between 6.6 and 8.2 kpc. We compare these results with present-day understanding of the spiral structure of the Galaxy and suggest that they trace the outer arm. This range of distances challenges current Galactic models adopting a disk cutoff at 14 kpc from the Galactic center. The young dwarfs overlap in space with an older component, which is identified as an old Galactic thin disk. Both young and old populations are confined in space since the disk is warped at the latitude and longitude of Tombaugh 1. The main effects of the warp are that the line of sight intersects the disk and entirely crosses it at the outer arm distance and that there are no traces of the closer Perseus arm, which would then be either unimportant in this sector or located much closer to the formal Galactic plane. Finally, we analyze a group of giant stars, which turn out to be located at very different distances and to possess very different chemical properties, with no obvious relation to the other populations.