scholarly journals 2D kinematics of massive stars near the Galactic Centre

2020 ◽  
Vol 500 (3) ◽  
pp. 3213-3239
Author(s):  
Mattia Libralato ◽  
Daniel J Lennon ◽  
Andrea Bellini ◽  
Roeland van der Marel ◽  
Simon J Clark ◽  
...  
Keyword(s):  
Moving Objects ◽  
Hubble Space Telescope ◽  
Massive Stars ◽  
Line Of Sight ◽  
Galactic Centre ◽  
Harsh Environment ◽  
Proper Motions ◽  
Sgr A ◽  
Better Than ◽  
Rule Out

ABSTRACT The presence of massive stars (MSs) in the region close to the Galactic Centre (GC) poses several questions about their origin. The harsh environment of the GC favours specific formation scenarios, each of which should imprint characteristic kinematic features on the MSs. We present a 2D kinematic analysis of MSs in a GC region surrounding Sgr A* based on high-precision proper motions obtained with the Hubble Space Telescope. Thanks to a careful data reduction, well-measured bright stars in our proper-motion catalogues have errors better than 0.5 mas yr−1. We discuss the absolute motion of the MSs in the field and their motion relative to Sgr A*, the Arches, and the Quintuplet. For the majority of the MSs, we rule out any distance further than 3–4 kpc from Sgr A* using only kinematic arguments. If their membership to the GC is confirmed, most of the isolated MSs are likely not associated with either the Arches or Quintuplet clusters or Sgr A*. Only a few MSs have proper motions, suggesting that they are likely members of the Arches cluster, in agreement with previous spectroscopic results. Line-of-sight radial velocities and distances are required to shed further light on the origin of most of these massive objects. We also present an analysis of other fast-moving objects in the GC region, finding no clear excess of high-velocity escaping stars. We make our astro-photometric catalogues publicly available.

scholarly journals The Hipparcos Extragalactic Link

1995 ◽  
Vol 166 ◽  
pp. 127-132 ◽  
Author(s):  
Jean Kovalevsky
Keyword(s):  
Reference Frames ◽  
Hubble Space Telescope ◽  
Visible Spectrum ◽  
Proper Motions ◽  
Time Intervals ◽  
Hipparcos Catalogue ◽  
Celestial Reference System ◽  
Celestial Reference Frame ◽  
Galactic Radio ◽  
Better Than

In conformity with the IAU resolutions on reference frames adopted in 1991, the Hipparcos catalogue will represent, in the visible spectrum, the celestial reference system defined by fixed positions of extra-galactic radio-sources. This will be realized by the strongest possible link between the IERS celestial reference frame with positions and/or proper motions of the largest possible number of Hipparcos stars determined also with respect to extragalactic objects. The data which will be used must be available before April 1995. It will include the following: positions and proper motions of radio stars observed by VLBI, VLA and MERLIN; photographic positions in fields including quasars; proper motions with respect to galaxies of the Lick, Yale, and Kiev programs, proper motions derived from pairs of photographic plates taken at large time intervals; and possibly data acquired by Hubble Space Telescope and from Earth's rotation data. The organization of the tasks within the working group is briefly described. The final accuracy of the link is expected to be of the order of, or better than, half a milliarcsecond.

scholarly journals Expansion parallaxes and intrinsic stellar properties for 15 simple planetary nebulae

2016 ◽  
Vol 12 (S323) ◽  
pp. 354-356 ◽  
Author(s):  
Detlef Schönberner ◽  
Ralf Jacob ◽  
Bruce Balick
Keyword(s):  
Hubble Space Telescope ◽  
Planetary Nebulae ◽  
Line Of Sight ◽  
Radiation Hydrodynamics ◽  
Proper Motions ◽  
Imaging Data ◽  
The Difference ◽  
Stellar Properties ◽  
Angular Expansion ◽  
Shock Fronts

AbstractWe determined individual distances to a small number of rather round, quite regularly shaped planetary nebulae by combining their angular expansion in the plane of the sky with a spectroscopically measured expansion along the line of sight. For this goal, we combined up to three epochs of Hubble Space Telescope imaging data and determined the respective proper motions of rim and shell edges, and of other features as well. Ground-based radial velocities are assigned separately to the nebular rims and shells and used to determine individual distances, thereby assuming that the expansions in the line-of-sight and in the plane of sky are equal. We employed 1D radiation-hydrodynamics simulations of planetary nebulae evolution to correct for the difference between the spectroscopically measured expansion velocities of rim and shell and the expansion speeds of their respective shock fronts.

scholarly journals Accurate mass estimates from the proper motions of dispersion-supported galaxies

2020 ◽  
Vol 493 (4) ◽  
pp. 5825-5837 ◽  
Author(s):  
Alexandres Lazar ◽  
James S Bullock
Keyword(s):  
Dark Matter ◽  
Proper Motion ◽  
Cold Dark Matter ◽  
Dwarf Galaxy ◽  
Tangential Velocity ◽  
Line Of Sight ◽  
Proper Motions ◽  
Characteristic Radius ◽  
Motion Measurements ◽  
Rule Out

ABSTRACT We derive a new mass estimator that relies on internal proper motion measurements of dispersion-supported stellar systems, one that is distinct and complementary to existing estimators for line-of-sight velocities. Starting with the spherical Jeans equation, we show that there exists a radius where the mass enclosed depends only on the projected tangential velocity dispersion, assuming that the anisotropy profile slowly varies. This is well-approximated at the radius where the log-slope of the stellar tracer profile is −2: r−2. The associated mass is $M(r_{-2}) = 2 G^{-1} \langle \sigma _{\mathcal {T}}^{2}\rangle ^{*} r_{-2}$ and the circular velocity is $V^{2}({r_{-2}}) = 2\langle \sigma _{\mathcal {T}}^{2}\rangle ^{*}$. For a Plummer profile r−2 ≃ 4Re/5. Importantly, r−2 is smaller than the characteristic radius for line-of-sight velocities derived by Wolf et al. Together, the two estimators can constrain the mass profiles of dispersion-supported galaxies. We illustrate its applicability using published proper motion measurements of dwarf galaxies Draco and Sculptor, and find that they are consistent with inhabiting cuspy NFW subhaloes of the kind predicted in CDM but we cannot rule out a core. We test our combined mass estimators against previously published, non-spherical cosmological dwarf galaxy simulations done in both cold dark matter (CDM; naturally cuspy profile) and self-interacting dark matter (SIDM; cored profile). For CDM, the estimates for the dynamic rotation curves are found to be accurate to $10\rm { per\, cent}$ while SIDM are accurate to $15\rm { per\, cent}$. Unfortunately, this level of accuracy is not good enough to measure slopes at the level required to distinguish between cusps and cores of the type predicted in viable SIDM models without stronger priors. However, we find that this provides good enough accuracy to distinguish between the normalization differences predicted at small radii (r ≃ r−2 < rcore) for interesting SIDM models. As the number of galaxies with internal proper motions increases, mass estimators of this kind will enable valuable constraints on SIDM and CDM models.

scholarly journals Gaia pulsars and where to find them

2020 ◽  
Vol 501 (1) ◽  
pp. 1116-1126
Author(s):  
John Antoniadis
Keyword(s):  
Massive Stars ◽  
Selection Effects ◽  
Millisecond Pulsar ◽  
Current Sensitivity ◽  
Empirical Relations ◽  
Supernova Explosions ◽  
Merger Rate ◽  
Kinematic Properties ◽  
Better Than ◽  
Rule Out

ABSTRACT While the majority of massive stars have a stellar companion, most pulsars appear to be isolated. Taken at face value, this suggests that most massive binaries break apart due to strong natal kicks received in supernova explosions. However, the observed binary fraction can still be subject to strong selection effects, as monitoring of newly discovered pulsars is rarely carried out for long enough to conclusively rule out multiplicity. Here, we use the second Gaia data release to search for companions to 1534 rotation-powered pulsars with positions known to better than 0.5 arcsec. We find 22 matches to known pulsars, including 1 not reported elsewhere, and 8 new possible companions to young pulsars. We examine the photometric and kinematic properties of these systems and provide empirical relations for identifying Gaia sources with potential millisecond pulsar companions. Our results confirm that the observed multiplicity fraction is small. However, we show that the number of binaries below the sensitivity of Gaia and radio timing in our sample could still be significantly higher. We constrain the binary fraction of young pulsars to be $f_{\rm young}^{\rm true}\le 5.3(8.3){{\ \rm per\ cent}}$ under realistic (conservative) assumptions for the binary properties and current sensitivity thresholds. For massive stars (≥10 M⊙) in particular, we find $f_{\rm OB}^{\rm true}\le 3.7{{\ \rm per\ cent}}$, which sets a firm independent upper limit on the Galactic neutron star merger rate, ≤7.2 × 10−4 yr−1. Ongoing and future projects, such as the CHIME/pulsar program, MeerTime, HIRAX, and ultimately the SKA, will significantly improve these constraints in the future.

scholarly journals 9.1. HST detections of massive black holes in the centers of galaxies

1998 ◽  
Vol 184 ◽  
pp. 377-384 ◽  
Author(s):  
H.C. Ford ◽  
Z.I. Tsvetanov ◽  
L. Ferrarese ◽  
W. Jaffe
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Hubble Space Telescope ◽  
Spherical Aberration ◽  
Proper Motions ◽  
Black Hole Mass ◽  
Massive Black Holes ◽  
The Galaxy ◽  
Ngc 1068 ◽  
Better Than

After correcting spherical aberration in the Hubble Space Telescope in 1993, the central masses of galaxies can be measured with a resolution 5 to 10 times better than can be achieved at the best terrestrial sites. This improvement in resolution is decisive for detecting the gravitational signature of massive black holes in galaxy nuclei. The discovery of small (r ~ 100–200 pc) rotating gaseous and stellar disks in the centers of many early-type galaxies provides a new and efficient means for measuring the central potentials of galaxies. Concomitantly, VLBI observations of H2O masers in the nuclei of NGC 4258 and NGC 1068 revealed exquisite Keplerian rotation curves around massive black holes at radii as small as 0.1 pc. Recent terrestrial K-band measurements of the proper motions of stars in the cluster at the center of the galaxy provide irrefutable evidence for a black hole with a mass of 2.7 × 106M⊙. At the time of this symposium, the presence of central massive black holes has been established in 12 galaxies. The evidence suggests that there are massive black holes in the centers of all AGNs and in most, if not all, nucleated galaxies. The present data show at best a weak correlation between black hole mass and bulge luminosity.

scholarly journals Local Group Proper Motion Dynamics

2014 ◽  
Vol 10 (S311) ◽  
pp. 1-10 ◽  
Author(s):  
Roeland P. van der Marel
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
Solar Neighborhood ◽  
Line Of Sight ◽  
Proper Motions ◽  
Dynamical Models ◽  
The Past ◽  
Tidal Streams

AbstractOur knowledge of the dynamics and masses of galaxies in the Local Group has long been limited by the fact that only line-of-sight velocities were observationally accessible. This introduces significant degeneracies in dynamical models, which can only be resolved by measuring also the velocity components perpendicular to the line of sight. However, beyond the solar neighborhood, the corresponding proper motions have generally been too small to measure. This has changed dramatically over the past decade, especially due to the angular resolution and stability available on the Hubble Space Telescope. Proper motions can now be reliably measured throughout the Local Group, as illustrated by, e.g., the work of the HSTPROMO collaboration. In this review, I summarize the importance of proper motions for Local Group science, and I describe the current and future observational approaches and facilities available to measure proper motions. I highlight recent results on various Milky Way populations (globular clusters, the bulge, the metal-poor halo, hypervelocity stars, and tidal streams), dwarf satellite galaxies, the Magellanic Clouds and the Andromeda System.

scholarly journals CPC2 Reduction with Hipparcos and Proper Motions in The Southern Hemisphere

1998 ◽  
Vol 11 (1) ◽  
pp. 551-551
Author(s):  
N. Zacharias ◽  
M.I. Zacharias ◽  
C. de Vegt ◽  
C.A. Murray
Keyword(s):  
Southern Hemisphere ◽  
Systematic Errors ◽  
Reference Star ◽  
Proper Motions ◽  
Positional Accuracy ◽  
Star Catalog ◽  
Naval Observatory ◽  
Celestial Reference System ◽  
First Time ◽  
Better Than

The Second Cape Photographic Catalog (CPC2) contains 276,131 stars covering the entire Southern Hemisphere in a 4-fold overlap pattern. Its mean epoch is 1968, which makes it a key catalog for proper motions. A new reduction of the 5687 plates using on average 40 Hipparcos stars per plate has resulted in a vastly improved catalog with a positional accuracy of about 40 mas (median value) per coordinate, which comes very close to the measuring precision. In particular, for the first time systematic errors depending on magnitude and color can be solved unambiguously and have been removed from the catalog. In combination with the Tycho Catalogue (mean epoch 1991.25) and the upcoming U.S. Naval Observatory CCD Astrograph Catalog (UCAC) project proper motions better than 2 mas/yr can be obtained. This will lead to a vastly improved reference star catalog in the Southern Hemisphere for the final Astrographic Catalogue (AC) reductions, which will then provide propermotions for millions of stars when combined with new epoch data. These data then will allow an uncompromised reduction of the southern Schmidt surveys on the International Celestial Reference System (ICRS).

scholarly journals Maser, infrared and optical emission for late-type stars in the Galactic plane

2017 ◽  
Vol 13 (S336) ◽  
pp. 184-186
Author(s):  
L. H. Quiroga-Nuñez ◽  
H. J. van Langevelde ◽  
L. O. Sjouwerman ◽  
Y. M. Pihlström ◽  
M. J. Reid ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Population Distribution ◽  
Massive Stars ◽  
Optical Emission ◽  
Proper Motions ◽  
Late Type ◽  
Intrinsic Properties ◽  
Radio Observations ◽  
Evolved Stars

AbstractRadio astrometric campaigns using VLBI have provided distances and proper motions for masers associated with young massive stars (BeSSeL survey). The ongoing BAaDE project plans to obtain astrometric information of SiO maser stars located in the inner Galaxy. These stars are associated with evolved, mass-losing stars. By overlapping optical (Gaia), infrared (2MASS, MSX and WISE) and radio (BAaDE) sources, we expect to obtain important clues on the intrinsic properties and population distribution of late-type stars. Moreover, a comparison of the Galactic parameters obtained with Gaia and VLBI can be done using radio observations on different targets: young massive stars (BeSSeL) and evolved stars (BAaDE).

scholarly journals Measuring proper motions of galactic dwarf galaxies with Hubble Space Telescope

2007 ◽  
Vol 3 (S248) ◽  
pp. 244-247 ◽  
Author(s):  
S. Piatek ◽  
C. Pryor
Keyword(s):  
Research Group ◽  
Dwarf Galaxies ◽  
Hubble Space Telescope ◽  
Proper Motions ◽  
Future Directions ◽  
Space Telescope ◽  
The Past ◽  
Scientific Justification ◽  
Satellite Galaxies ◽  
Using Data

AbstractOver the past several years, our research group has been measuring proper motions for nearby dwarf satellite galaxies using data taken with the Hubble Space Telescope. In order to measure proper motions with an expected size of several tens of milliarcseconds per century using a time baseline of 2-4 years, our work required that positions of stars and QSOs be measured to an accuracy of ~0.25 mas (~0.005 pixel). This contribution reviews the scientific justification of this work and our methodology. It concludes with a few general results and future directions.

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