scholarly journals The absolute proper motions of the Arches and Quintuplet clusters

2020 ◽  
Vol 497 (4) ◽  
pp. 4733-4741 ◽  
Author(s):  
Mattia Libralato ◽  
Mark Fardal ◽  
Daniel Lennon ◽  
Roeland P van der Marel ◽  
Andrea Bellini
Keyword(s):  
Reference System ◽  
Reference Frames ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Proper Motions ◽  
The Absolute ◽  
First Time ◽  
Massive Clusters ◽  
Gaia Dr2 ◽  
Shed Light

ABSTRACT Arches and Quintuplet are two young, massive clusters projected near the Galactic Centre. To date, studies focused on understanding their origin have been based on proper motions (PMs) derived in the clusters’ reference frames and required some assumptions about their 3D motion. In this paper, we combine public PM catalogues of these clusters with the Gaia DR2 catalogue and, for the first time, transform the relative PMs of the Arches and Quintuplet clusters on to an absolute reference system. We find that the absolute PM of the Arches is (μαcos δ, μδ) = (−1.45 ± 0.23, −2.68 ± 0.14) mas yr−1 and that of the Quintuplet is (μαcos δ, μδ) = (−1.19 ± 0.09, −2.66 ± 0.18) mas yr−1. These values suggest that these systems are moving almost parallel to the Galactic plane. A measurement of the clusters’ distances is still required to meaningfully constrain the clusters’ orbits and shed light on the origin of the Arches and Quintuplet.

scholarly journals The Arches cluster revisited

2019 ◽  
Vol 623 ◽  
pp. A84 ◽  
Author(s):  
J. S. Clark ◽  
M. E. Lohr ◽  
L. R. Patrick ◽  
F. Najarro
Keyword(s):  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Galactic Centre ◽  
Complete Dataset ◽  
Subsequent Determination ◽  
The Galaxy ◽  
First Time ◽  
Massive Clusters

The Arches is one of the youngest, densest and most massive clusters in the Galaxy. As such it provides a unique insight into the lifecycle of the most massive stars known and the formation and survival of such stellar aggregates in the extreme conditions of the Galactic Centre. In a previous study we presented an initial stellar census for the Arches and in this work we expand upon this, providing new and revised classifications for ∼30% of the 105 spectroscopically identified cluster members as well as distinguishing potential massive runaways. The results of this survey emphasise the homogeneity and co-evality of the Arches and confirm the absence of H-free Wolf-Rayets of WC sub-type and predicted luminosities. The increased depth of our complete dataset also provides significantly better constraints on the main sequence population; with the identification of O9.5 V stars for the first time we now spectroscopically sample stars with initial masses ranging from ∼16 M⊙ to ≥120 M⊙. Indeed, following from our expanded stellar census we might expect ≳50 stars within the Arches to have been born with masses ≳60 M⊙, while all 105 spectroscopically confirmed cluster members are massive enough to leave relativistic remnants upon their demise. Moreover the well defined observational properties of the main sequence cohort will be critical to the construction of an extinction law appropriate for the Galactic Centre and consequently the quantitative analysis of the Arches population and subsequent determination of the cluster initial mass function.

scholarly journals New ultracool dwarf neighbours within 20 pc from Gaia DR2

2020 ◽  
Vol 637 ◽  
pp. A45
Author(s):  
R.-D. Scholz
Keyword(s):  
Proper Motion ◽  
Visual Inspection ◽  
Near Infrared ◽  
Galactic Plane ◽  
Proper Motions ◽  
Magnitude Diagram ◽  
Motion Measurements ◽  
Moving Groups ◽  
Absolute Magnitudes ◽  
Gaia Dr2

Aims. The Gaia data release 2 (DR2) contains > 6000 objects with parallaxes (Plx + 3 × e_Plx) > 50 mas, placing them within 20 pc from the Sun. Because the expected numbers based on extrapolating the well-known 10 pc census are much lower, nearby Gaia stars need a quality assessment. The 20 pc sample of white dwarfs (WDs) has been verified and completed with Gaia DR2. We here confirm and complete the 20 pc sample of ultracool dwarfs (UCDs) with spectral types ≳M7 and given Gaia DR2 parallaxes. Methods. Dividing the Gaia DR2 20 pc sample into subsamples of various astrometric and photometric quality, we studied their distribution on the sky, in the MG versus G − RP colour-magnitude diagram (CMD), and as a function of G magnitude and total proper motion. After excluding 139 known WDs and 263 known UCDs from the CMD, we checked all remaining ≈3500 candidates with MG >  14 mag (used to define UCDs in this study) for the correctness of their Gaia DR2 proper motions by visual inspection of finder charts, comparison with proper motion catalogues, and comparison with our own proper motion measurements. For confirmed UCD candidates we estimated spectral types photometrically using Gaia and near-infrared absolute magnitudes and colours. Results. We failed to confirm new WDs, but found 50 new UCD candidates that are not mentioned in three previous studies using Gaia DR2. They have relatively small proper motions and low tangential velocities and are concentrated towards the Galactic plane. Half of them have spectral types in SIMBAD and/or previous non-Gaia distance estimates that placed them already within 20 pc. For 20 of the 50 objects, we estimated photometric spectral types of M6−M6.5, slightly below the classical UCD spectral type limit. However, seven L4.5−L6.5, four L0−L1, five M8.5−M9.5, and three M7−M8 dwarfs can be considered as completely new UCDs discoveries within 20 pc based on Gaia DR2. Four M6.5 and two L4.5 dwarfs have high membership probabilities (64%−99%) in the ARGUS, AB Doradus, or Carina Near young moving groups.

scholarly journals Internal motions in OB associations with Gaia DR2

2020 ◽  
Vol 493 (2) ◽  
pp. 2339-2351 ◽  
Author(s):  
A M Melnik ◽  
A K Dambis
Keyword(s):  
Expansion Velocity ◽  
Giant Molecular Clouds ◽  
Proper Motions ◽  
Ob Stars ◽  
Internal Motions ◽  
Ob Associations ◽  
Stellar Masses ◽  
Formation Efficiency ◽  
First Time ◽  
Gaia Dr2

ABSTRACT We study the motions inside 28 OB associations with the use of Gaia DR2 proper motions. The average velocity dispersion calculated for 28 OB associations including more than 20 stars with Gaia DR2 proper motion is σv = 4.5 km s−1. The median virial and stellar masses of OB associations are Mvir = 8.9 × 105 and Mst = 8.1 × 103 M⊙, respectively. The median star-formation efficiency in parent giant molecular clouds appears to be ϵ = 1.2 per cent. Gaia DR2 proper motions confirm the expansion in the Per OB1, Car OB1, and Sgr OB1 associations found earlier with Gaia DR1 data. We also detect the expansion in Gem OB1, Ori OB1, and Sco OB1 associations, which became possible for the first time now when analysed with Gaia DR2 proper motions. The analysis of the distribution of OB stars in the Per OB1 association shows the presence of a shell-like structure with the radius of 40 pc. Probably, the expansion of the Per OB1 association started with the velocity greater than the present-day expansion velocity equal to 5.0 ± 1.7 km s−1.

scholarly journals The Distribution of Open Clusters in the Galaxy

2021 ◽  
Vol 8 ◽  
Author(s):  
Hektor Monteiro ◽  
Douglas A. Barros ◽  
Wilton S. Dias ◽  
Jacques R. D. Lépine
Keyword(s):  
Galactic Plane ◽  
Rotation Velocity ◽  
Open Clusters ◽  
Space Distribution ◽  
Proper Motions ◽  
Corotation Radius ◽  
The Galaxy ◽  
Galactic Abundance ◽  
Galactic Orbit ◽  
Gaia Dr2

In this work we explore the new catalog of galactic open clusters that became available recently, containing 1,750 clusters that have been re-analyzed using the Gaia DR2 catalog to determine the stellar memberships. We used the young open clusters as tracers of spiral arms and determined the spiral pattern rotation speed of the Galaxy and the corotation radius, the strongest Galactic resonance. The sample of open clusters used here is increased by dozens of objects with respect to our previous works. In addition, the distances and ages values are better determined, using improvements to isochrone fitting and including an updated extinction polynomial for the Gaia DR2 photometric band-passes, and the Galactic abundance gradient as a prior for metallicity. In addition to the better age determinations, the catalog contains better positions in the Galactic plane and better proper motions. This allow us to discuss not only the present space distribution of the clusters, but also the space distribution of the clusters's birthplaces, obtained by integration of the orbits for a time equal to their age. The value of the rotation velocity of the arms (28.5 ± 1.0 km s−1 kpc−1) implies that the corotation radius (Rc) is close to the solar Galactic orbit (Rc/R0 = 1.01±0.08), which is supported by other observational evidence discussed in this text. A simulation is presented, illustrating the motion of the clusters in the reference frame of corotation. We also present general statistics of the catalog of clusters, like spatial distribution, distribution relative to height from the Galactic plane, and distribution of ages and metallicity. An important feature of the space distribution, the corotation gap in the gas distribution and its consequences for the young clusters, is discussed.

scholarly journals Dating a Chalcolithic Burial Cave in Peqi'in, Upper Galilee, Israel

Radiocarbon ◽  
1997 ◽  
Vol 40 (2) ◽  
pp. 707-712 ◽  
Author(s):  
Dror Segal ◽  
Israel Carmi ◽  
Zvi Gal ◽  
Howard Smithline ◽  
Dina Shalem
Keyword(s):  
Main Phase ◽  
Major Significance ◽  
Societal Development ◽  
Development Period ◽  
Chalcolithic Period ◽  
Absolute Dating ◽  
The Absolute ◽  
First Time ◽  
Cave Use ◽  
Shed Light

In May 1995 an impressive karstic cave possessing dozens of burials dating to the main phase of the Chalcolithic Period (ca. 4500–3500 bce) was discovered in Peqi'in in the high hills of Galilee in northern Israel. It was subsequently excavated over the course of the following months. The large amount of unique ceramic ossuaries and the variety of burial offerings shed light, for the first time, on this critical societal development period in a region where its remains have rarely been found. Although the major significance of the cave is as a mortuary center, it was also utilized in a domestic capacity some centuries previously, during the generally less familiar Early Chalcolithic Period. We present here the dating of 22 14C samples collected from these separate phases of cave use. Their interpretation should aid in understanding of the absolute dating of the Chalcolithic Period and its relation to the period preceding its inception.

scholarly journals VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk

2020 ◽  
Vol 642 ◽  
pp. L19
Author(s):  
E. R. Garro ◽  
D. Minniti ◽  
M. Gómez ◽  
J. Alonso-García ◽  
R. H. Barbá ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Near Infrared ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Ring Structure ◽  
Galactic Centre ◽  
Distance Modulus ◽  
Proper Motions ◽  
Optical Photometry

Context. Milky Way globular clusters (GCs) are difficult to identify at low Galactic latitudes because of high differential extinction and heavy star crowding. The new deep near-infrared (IR) images and photometry from the VISTA Variables in the Via Láctea Extended Survey (VVVX) allow us to chart previously unexplored regions. Aims. Our long term aim is to complete the census of Milky Way GCs. The immediate goals are to estimate the astrophysical parameters for the newly discovered GC candidates, measuring their reddenings, extinctions, distances, total luminosities, proper motions, sizes, metallicities, and ages. Methods. We used the near-IR VVVX survey database, in combination with the optical photometry and proper motions (PMs) from Gaia Data Release 2 (DR2), and with the Two Micron All Sky Survey photometry to search for and characterise new GCs within the southern Galactic plane (|b| < 5°). Results. We report the detection of a heretofore unknown Galactic GC at RA = 14:09:00.0; Dec = −65:37:12 (J2000) corresponding to l = 310.828 deg; and b = −3.944 deg in galactic coordinates. We calculate a reddening of E(J − Ks) = (0.3 ± 0.03) mag and an extinction of AKs = (0.15 ± 0.01) mag for this new GC. Its distance modulus and corresponding distance were measured as (m − M) = (15.93 ± 0.03) mag and D = (15.5 ± 1.0) kpc, respectively. We also estimate the metallicity and age by comparison with known GCs and by fitting PARSEC and Dartmouth isochrones, finding [Fe/H] = ( − 0.70 ± 0.2) dex and t = (11.0 ± 1.0) Gyr. The mean GC PMs from Gaia DR2 are μα* = ( − 4.68 ± 0.47) mas yr−1 and μδ = ( − 1.34 ± 0.45) mas yr−1. The total luminosity of our cluster is estimated to be MKs = ( − 7.76 ± 0.5) mag. The core and tidal radii from the radial density profile are rc ∼ 2.1′ (4.6 pc) and rt = 6.5′ (14.6 pc) at the cluster distance. Conclusions. We have found a new low luminosity, old and metal-rich GC, situated in the far side of the Galactic disk at RG = 11.2 kpc from the Galactic centre and at z = 1.0 kpc below the plane. Interestingly, the location, metallicity, and age of this GC are coincident with the Monoceros ring structure.

scholarly journals The disruption of the low-mass globular cluster E 3

2020 ◽  
Vol 499 (2) ◽  
pp. 2157-2161
Author(s):  
Julio A Carballo-Bello ◽  
Ricardo Salinas ◽  
Andrés E Piatti
Keyword(s):  
Globular Cluster ◽  
Surface Brightness ◽  
Galactic Centre ◽  
Proper Motions ◽  
Tidal Disruption ◽  
Low Surface Brightness ◽  
Low Mass ◽  
Important Amount ◽  
Tidal Tails ◽  
Gaia Dr2

ABSTRACT We use Gaia DR2 photometry and proper motions to search for the hypothetical tidal tails of the Galactic globular cluster E 3. Using a modified version of a classical decontamination procedure, we are able to identify the presence of an extended structure emerging from the cluster up to r ∼ 1 deg from its centre, thus suggesting that this poorly studied cluster is undergoing a tidal disruption process. These low surface brightness structures are aligned with the direction to the Galactic centre, as expected for a cluster close to its perigalacticon. Different scenarios to explain the important amount of mass lost by this cluster are discussed.

scholarly journals Excited-state hydroxyl maser catalogue from the methanol multibeam survey – I. Positions and variability

2016 ◽  
Vol 461 (1) ◽  
pp. 136-155 ◽  
Author(s):  
A Avison ◽  
L J Quinn ◽  
G A Fuller ◽  
J L Caswell ◽  
J A Green ◽  
...  
Keyword(s):  
Excited State ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Detection Rates ◽  
Survey Finding ◽  
First Time ◽  
Galactic Longitude ◽  
Compact Array

Abstract We present the results of the first complete unbaised survey of the Galactic plane for 6035-MHz excited-state hydroxyl (ex-OH) masers undertaken as part of the methanol multibeam (MMB) survey. These observations cover the Galactic longitude ranges 186° &lt; l &lt; 60° including the Galactic Centre. We report the detection of 127 ex-OH masers within the survey region, 47 being new sources. The positions of new detections were determined from interferometric observations with the Australia Telescope Compact Array. We discuss the association of 6035-MHz masers in our survey with the 6668-MHz masers from the MMB Survey, finding 37 likely CH3OH–ex-OH maser pairs with physical separations of ≤0.03 pc and 55 pairings separated by ≤0.1 pc. Using these we calculate for the first time an ex-OH maser lifetime of between 3.3 × 103 and 8.3 × 103 yr. We also discuss the variability of the 6035-MHz masers and detection rates of counterpart 6030-MHz ex-OH masers (28 per cent of our sample having detection at both frequencies).

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

Aleksey Peshkov as an editor of Samarskaya Gazeta

2020 ◽  
pp. 128-138
Author(s):  
A. S. Bik-Bulatov
Keyword(s):  
Local History ◽  
Organizational Skills ◽  
First Time ◽  
New Evidence ◽  
Insight Into ◽  
Shed Light

The article uses little known letters of M. Gorky, many of which were published for the first time in 1997, as well as findings of Samara-based experts in local history to shed light on the writer’s work as editor-in-chief of the Samarskaya Gazeta newspaper in 1895. The researcher introduces hitherto unstudied reminiscences of the journalist D. Linyov (Dalin) about this period, which reference a letter by Gorky, now lost. The paper details a newly discovered episode of Gorky’s professional biography as a journalist: it concerns his campaign against a Samara ‘she-wolf,’ the madam of a local brothel A. Neucheva. Linyov’s reminiscences turn out to be an important and interesting source, offering an insight into the daily grind of the young editor Gorky, providing new evidence of his excellent organizational skills, and describing his moral and social stance. The author presents his work in the context of a recently initiated broader discussion about the need to map out all Russian periodicals for the period until 1917, as well as all research devoted to individual publications.

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