scholarly journals OH/IR Stars Near the Galactic Centre

1983 ◽  
Vol 103 ◽  
pp. 542-543
Author(s):  
H.J. Habing ◽  
F.M. Olnon ◽  
A. Winnberg ◽  
H.E. Matthews ◽  
B. Baud
Keyword(s):  
Spatial Distribution ◽  
High Velocity ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Red Giants ◽  
Large Array ◽  
Very Large Array ◽  
Ir Stars

We have detected 34 OH/IR stars within 1 degree of the galactic centre by their OH emission line at 1612 MHz (18 cm) using the Effelsberg 100 m telescope and the Very Large Array. The spatial distribution and the distribution of the radial velocities show that practically all stars are within 150 pc from the Galactic centre, and that the number of foreground objects is very small. The projected distribution of the stars is similar to that of the surface brightness at 2.4 μm. Since the 2.4 μm radiation is supposed to be due to red giants, the OH/IR stars are probably members of the same population. The stars have considerable random velocities (velocity dispersion in one coordinate of 150 ± 50 km s−1), but show general Galactic rotation. The high velocity dispersion is remarkable for objects of this population.

Looking for new water-fountain stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 527-528
Author(s):  
L. Uscanga ◽  
J. F. Gómez ◽  
B. H. K. Yung ◽  
H. Imai ◽  
J. R. Rizzo ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Magnetic Fields ◽  
Mass Loss ◽  
High Velocity ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Evolved Stars

AbstractWe carried out simultaneous observations of H2O and OH masers, and radio continuum at 1.3 cm with the Karl G. Jansky Very Large Array (VLA) towards 4 water-fountain candidates. Water fountains (WFs) are evolved stars, in the AGB and post-AGB phase, with collimated jets traced by high-velocity H2O masers. Up to now, only 15 sources have been confirmed as WFs through interferometric observations. We are interested in the discovery and study of new WFs. A higher number of these sources is important to understand their properties as a group, because they may represent one of the first manifestations of collimated mass-loss in evolved stars. These observations will provide information about the role of magnetic fields in the launching of jets in WFs. Our aim is to ascertain the WF nature of these candidates, and investigate the spatial distribution of the H2O and OH masers.

Very Large Array Observations of High‐Velocity Hiin L1551

2000 ◽  
Vol 538 (2) ◽  
pp. 728-737 ◽  
Author(s):  
C. Giovanardi ◽  
L. F. Rodriguez ◽  
S. Lizano ◽  
J. Canto
Keyword(s):  
High Velocity ◽  
Large Array ◽  
Very Large Array

scholarly journals VLA Observations of Planetary Nebulae at the Galactic Centre

1983 ◽  
Vol 103 ◽  
pp. 423-424
Author(s):  
R. Gathier ◽  
S.R. Pottasch ◽  
W.M. Goss ◽  
J.H. van Gorkom
Keyword(s):  
New Mexico ◽  
Detection Limit ◽  
Selection Effect ◽  
Planetary Nebulae ◽  
Radial Velocities ◽  
Galactic Centre ◽  
Large Array ◽  
Very Large Array ◽  
Instrumental Resolution

The Very Large Array (VLA) in Socorro, New Mexico, has been used to measure the 6 cm continuum flux densities and the angular sizes of 42 planetary nebulae (PN) in the direction of the galactic centre (GC). These were all optically confirmed PN for which the radial velocities (and positions on the sky) make it very likely that they are close to the GC. With a detection limit of about 1 mJy, 34 PN were detected. Their flux densities range from 2 to 100 mJy. Initially we used a configuration of the VLA with an instrumental resolution of 1″. About 80% of the detected PN could be clearly resolved with this resolution. The unresolved PN were observed again with a configuration of the VLA that has a resolution of 0″.4. For all but one of the 34 detected PN we could determine reliable angular sizes. The inferred total ionized masses range from < 0.01 to ~ 0.5 M⊙, assuming a distance to the GC of 9 kpc. The results argue strongly against the use of the Shklovsky method for distance determinations. Previous measurements of PN at the GC showed that their luminosities were substantially higher than those for nearby PN (Pottasch, 1980). The luminosity distribution of the PN in our sample is broader towards lower luminosities (up to the detection limit of the observations), but the luminosities are still high compared with nearby PN. We interpret this as a selection effect: by studying only optically confirmed PN, the intrinsically brightest PN are selected.

scholarly journals VLA Observations of Sgr A

1983 ◽  
Vol 101 ◽  
pp. 65-69
Author(s):  
W. M. Goss ◽  
U. J. Schwarz ◽  
R. D. Ekers ◽  
J. H. van Gorkom
Keyword(s):  
Surface Brightness ◽  
Supernova Remnant ◽  
Crab Nebula ◽  
Galactic Centre ◽  
Thermal Source ◽  
Very Large Array ◽  
Sgr A ◽  
Cas A ◽  
Relationship Of ◽  
The Crab Nebula

The radio source Sgr A has been mapped with the Very Large Array (VLA) at 6 and 20 cm with an angular resolution of 5″ x 8″ arc. In agreement with the earlier “WORST” map, the non-thermal source Sgr A East shows a shell structure, while the thermal source Sgr A West shows a spiral-like morphology. We suggest that Sgr A East is a supernova remnant (SNR) near the galactic centre. Its surface brightness is the third largest in our galaxy after Cas A and the Crab Nebula. The diameter is 9 pc and the source fits the surface-brightness diameter relationship of Clark and Caswell (1976) if a distance of 10 kpc is assumed.

scholarly journals Calibrating the BHB star distance scale and the halo kinematic distance to the Galactic Centre

2020 ◽  
Vol 499 (1) ◽  
pp. 1058-1071
Author(s):  
Nikita D Utkin ◽  
Andrei K Dambis
Keyword(s):  
Velocity Dispersion ◽  
Anisotropy Parameter ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Galactocentric Distance ◽  
Absolute Value ◽  
Dispersion Tensor ◽  
Rr Lyrae ◽  
Parameter Values

ABSTRACT We report the first determination of the distance to the Galactic Centre based on the kinematics of halo objects. We apply the statistical-parallax technique to the sample of ∼2500 blue horizontal branch (BHB) stars compiled by Xue et al. to simultaneously constrain the correction factor to the photometric distances of BHB stars as reported by those authors and the distance to the Galactic Centre to find R = 8.2 ± 0.6 kpc. We also find that the average velocity of our BHB star sample in the direction of Galactic rotation, V0 = −240 ± 4 km s−1, is greater by about 20 km s−1 in absolute value than the corresponding velocity for halo RR Lyrae type stars (V0 = −222 ± 4 km s−1) in the Galactocentric distance interval from 6 to 18 kpc, whereas the total (σV) and radial (σr) velocity dispersion of the BHB sample are smaller by about 40–45 km s−1 than the corresponding parameters of the velocity dispersion ellipsoid of halo RR Lyrae type variables. The velocity dispersion tensor of halo BHB stars proved to be markedly less anisotropic than the corresponding tensor for RR Lyrae type variables: the corresponding anisotropy parameter values are equal to βBHB = 0.51 ± 0.02 and βRR = 0.71 ± 0.03, respectively.

scholarly journals OH/IR Stars Near the Galactic Centre

1977 ◽  
Vol 42 ◽  
pp. 438-445
Author(s):  
B. Baud
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Ambient Medium ◽  
Relative Increase ◽  
Galactic Centre ◽  
Ir Stars ◽  
Large Velocity ◽  
The Galaxy ◽  
Circumstellar Shell

AbstractObservations at 1612 MHz around the Galactic Centre have revealed the existence of 43 OH/IR stars. Sources within 6° longitude from the Galactic Centre appear to be associated with the central parts of the Galaxy. They have a large velocity dispersion and a mean radial velocity of 0 km s−1, indicating that there is no net rotation around the Centre. Within 2° from the Centre there is a strong relative increase in the number of sources with a velocity separation between the two emission peaks of less than 30 km s−1. This is discussed in terms of a possible interaction between the circumstellar shell and the ambient medium.

scholarly journals VLA Observations of the Galactic Centre at 74 MHz

2002 ◽  
Vol 199 ◽  
pp. 272-273
Author(s):  
K. R. Anantharamaiah ◽  
Namir E. Kassim ◽  
T.J.W. Lazio ◽  
W.M. Goss ◽  
H. Falcke
Keyword(s):  
Galactic Centre ◽  
Large Array ◽  
Very Large Array ◽  
Centre Region

We present a preliminary image of the Galactic Centre region at 74 MHz made using the Very Large Array (VLA)

The Cosmic Mystery Tour

2019 ◽  
Author(s):  
Nicholas Mee
Keyword(s):  
Science Fiction ◽  
Particle Physics ◽  
Cultural Context ◽  
Big Bang ◽  
Galactic Centre ◽  
Red Giants ◽  
Extraterrestrial Life ◽  
Modern Physics ◽  
Recent Developments ◽  
The Universe

The Cosmic Mystery Tour is a brief account of modern physics and astronomy presented in a broad historical and cultural context. The book is attractively illustrated and aimed at the general reader. Part I explores the laws of physics including general relativity, the structure of matter, quantum mechanics and the Standard Model of particle physics. It discusses recent discoveries such as gravitational waves and the project to construct LISA, a space-based gravitational wave detector, as well as unresolved issues such as the nature of dark matter. Part II begins by considering cosmology, the study of the universe as a whole and how we arrived at the theory of the Big Bang and the expanding universe. It looks at the remarkable objects within the universe such as red giants, white dwarfs, neutron stars and black holes, and considers the expected discoveries from new telescopes such as the Extremely Large Telescope in Chile, and the Event Horizon Telescope, currently aiming to image the supermassive black hole at the galactic centre. Part III considers the possibility of finding extraterrestrial life, from the speculations of science fiction authors to the ongoing search for alien civilizations known as SETI. Recent developments are discussed: space probes to the satellites of Jupiter and Saturn; the discovery of planets in other star systems; the citizen science project SETI@Home; Breakthrough Starshot, the project to develop technologies to send spacecraft to the stars. It also discusses the Fermi paradox which argues that we might actually be alone in the cosmos

Multiwavelength analysis of OH Megamaser galaxies: The case of IRAS11506-3851

2020 ◽  
Vol 15 (S359) ◽  
pp. 347-349
Author(s):  
Carpes P. Hekatelyne ◽  
Thaisa Storchi-Bergmann
Keyword(s):  
Active Galactic Nuclei ◽  
Hubble Space Telescope ◽  
Galactic Nuclei ◽  
Large Array ◽  
Very Large Array ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Unit ◽  
Mixed Transition ◽  
Integral Field

AbstractWe present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.

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