The Sun’s distance from the Galactic Centre and mid-plane, and the Galactic old bulge’s morphology: 715 VVV Type II Cepheids

2021 ◽  
Vol 502 (3) ◽  
pp. 4194-4198
Author(s):  
Evgeny Griv ◽  
Michael Gedalin ◽  
Pawel Pietrukowicz ◽  
Daniel Majaess ◽  
Ing-Guey Jiang
Keyword(s):  
Statistical Method ◽  
High Latitude ◽  
Gravitational Lensing ◽  
Near Infrared ◽  
Major Axis ◽  
Galactic Centre ◽  
The Sun ◽  
Type Ii ◽  
Infrared Observations ◽  
Centrally Symmetric

ABSTRACT A statistical method is employed in tandem with new VISTA Variables in the Via Lactea (VVV) near-infrared observations to determine the Sun’s distance from the Galactic Centre (r0, GC), the Sun’s height from the local mid-plane (z0), and to likewise infer the shape of the Galactic ∼10 Gyr old bulge. Specifically, the conclusions stem from an investigation of 715 high-latitude (|b| > 1°) and centrally symmetric concentrated Type II Cepheids (T2Cs) recently identified in the VVV survey by Braga et al. The analysis yields r0 = 8.35 ± 0.10 kpc and z0 = 10 ± 2 pc. The T2Cs distribution within the effective bulge radius rbulge = 2–3 kpc is an ellipsoid exhibiting axial ratios of ≈1:0.7:0.6, with the major axis inclined at an angle θ ≈ −3° to the Sun–GC sightline. T2Cs do not trace a prominent barred structure at distances >1 kpc from the GC. A key conclusion is that analyses of independent optical and infrared Optical Gravitational Lensing Experiment (OGLE) and VVV observations yield consistent results (e.g. r0 > 8.0 kpc and both observations display a comparable shape of an ellipsoid), thus providing a constrained and reduced systematic uncertainty.

scholarly journals The Distance and Orientation of the Galactic Bulge from Mira Variables: A Preliminary Report

1999 ◽  
Vol 192 ◽  
pp. 89-94 ◽  
Author(s):  
R. M. Catchpole ◽  
P. A. Whitelock ◽  
M. W. Feast ◽  
S.M.G. Hughes ◽  
C. Alard ◽  
...  
Keyword(s):  
Preliminary Report ◽  
Near Infrared ◽  
Major Axis ◽  
Galactic Centre ◽  
Spherically Symmetric ◽  
Axis Ratio ◽  
Circular Symmetry ◽  
Mira Variables ◽  
Axis Of Rotation ◽  
Scale Length

Near-infrared, JHKL, observations of 595 Mira variables in two fields on either side of the centre of our Galaxy, confirm that the Bulge is not spherically symmetric about its axis of rotation, but is elongated so that the part to the east of the centre is closer to us. The shape of the Bulge about its axis of rotation is not uniquely defined by these data, but the shape that deviates least from circular symmetry has an axis ratio xo/yo = 1.7, with a major axis at an angle, θ = 58° ± 7, to the plane of the sky, for a galactic centre distance, R0 = 9.4 ± 0.5 kpc. This is based on an assumed scale length in galactic coordinates of bo = 375 pc and lo/bo = 2.0.

scholarly journals Radio, Millimeter and Infrared Observations of the Local Hot Bubble and Its Environment

1997 ◽  
Vol 166 ◽  
pp. 199-210
Author(s):  
Ulrich Mebold ◽  
Jürgen Kerp ◽  
Peter M.W. Kalberla
Keyword(s):  
High Latitude ◽  
Molecular Clouds ◽  
Rapid Expansion ◽  
The Sun ◽  
Local Bubble ◽  
Infrared Observations ◽  
Neutral Gas ◽  
The Mean ◽  
Frequency Window ◽  
Definition Of

AbstractWe present a definition of the local void of neutral gas from observations in the radio frequency window. We question the concept of the Local Bubble in sense of a more or less spherical volume which is surrounded by a shell of denser gas. The concept of the Local Bubble is challenged by the discovery of numerous neutral, dense clouds inside the local void. The search for a “shell” around the suspected Bubble has resulted only in inconclusive findings so far. The sample of high latitude molecular clouds illustrates the situation particularly well. The statistical properties of their spatial distribution, e.g. the mean distance, seem to fit very nicely to the spatial extent of the Local Bubble. But a more detailed investigation shows that the concept of a bubble – in particular an expanding bubble – is not supported. We suggest that the local void is nothing more than a typical place in an interarm region of our Galaxy.Finally, a discussion of the high latitude boundary of the local void does not give strong evidence for the concept of a bubble, that has once been in rapid expansion and is still showing signs of interaction with its environment. However, indications for interactions of IVCs or HVCs with their surroundings are found. These hint at the presence of a gaseous disk which is much more vertically extended than previously believed, or at a Galactic wind which may be blowing from the Galactic neighbourhood of the Sun.

scholarly journals Cepheids and other variable stars and the distance to the Galactic Centre

2012 ◽  
Vol 8 (S289) ◽  
pp. 109-115
Author(s):  
Noriyuki Matsunaga
Keyword(s):  
Near Infrared ◽  
Variable Stars ◽  
Galactic Centre ◽  
Type Ii ◽  
Large Uncertainty ◽  
Monitoring Survey ◽  
Red Clump ◽  
Infrared Monitoring ◽  
Distance Indicators

AbstractWe review and discuss results of our survey of variable stars towards the Galactic Centre and their distances. In our near-infrared monitoring survey using IRSF/SIRIUS, we detected a number of Miras and Cepheids (both classical and type II) within 20 arcmin of the Galactic Centre. These distance indicators yield a distance to the Galactic Centre of between 7.5 and 8.5 kpc. A new calibration of the red clump also leads to a distance of ~ 8 kpc. For these indicators, which are luminosity-based, a large uncertainty resides in the correction for the foreground extinction, which depends on the reddening law. Nevertheless, our estimates are consistent with previous estimates based the kinematics of stars near the Galactic Centre, and this supports the reddening law we use.

The distance from the Sun to the centre and the shape of the old bulge in the Galaxy: 16 221 OGLE RR Lyrae stars

2020 ◽  
Vol 499 (1) ◽  
pp. 1091-1098
Author(s):  
Evgeny Griv ◽  
Michael Gedalin ◽  
Pawel Pietrukowicz ◽  
Daniel Majaess ◽  
Ing-Guey Jiang
Keyword(s):  
3D Structure ◽  
Axial Ratio ◽  
Major Axis ◽  
Space Distribution ◽  
Galactic Centre ◽  
The Sun ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Lyrae Stars

ABSTRACT A statistical method is used to determine both the Sun’s distance r0 from the Galactic Centre and the 3D structure of the old stellar population of the Galactic bulge. The space distribution of 16 221 high latitude type-RRab RR Lyrae stars from the optical OGLE survey located towards the bulge is explored. An estimate by using RR Lyraes leads to a mean r0 = 8.28 ± 0.14 kpc within the effective bulge radius of rbulge = 2–3 kpc. The distribution of RR Lyraes within rbulge has the shape of an ellipsoid slightly elongated almost towards the Sun with a major axis of its symmetry a and two minor axes b and c of about the same length. The axial ratio is a: b: c ≈ 1: 0.7: 0.7. These age-old, metal-poor, and kinematically hot stars do not trace a strong bar-like structure in the direction of the bulge at distances >1 kpc from the Galactic Centre, as b/a ∼ 1.

scholarly journals Accretion and Outflow Activity in the Earliest Phases of Star-Formation: CO, Sub-mm Continuum, and Near-Infrared Observations

1997 ◽  
Vol 163 ◽  
pp. 725-726
Author(s):  
K.-W. Hodapp ◽  
E. F. Ladd
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Point Sources ◽  
Spectral Energy ◽  
Infrared Observations ◽  
Circumstellar Material ◽  
Dense Cores ◽  
Wavelength Radiation ◽  
Main Component

Stars in the earliest phases of their formation, i.e., those accreting the main component of their final mass, are deeply embedded within dense cores of dust and molecular material. Because of the high line-of-sight extinction and the large amount of circumstellar material, stellar emission is reprocessed by dust into long wavelength radiation, typically in the far-infrared and sub-millimeter bands. Consequently, the youngest sources are strong submillimeter continuum sources, and often undetectable as point sources in the near-infrared and optical. The most deeply embedded of these sources have been labelled “Class 0” sources by André, Ward-Thompson, & Barsony (1994), in an extension of the spectral energy distribution classification scheme first proposed by Adams, Lada, & Shu (1987).

scholarly journals Comparison of satellite microwave backscattering (ASCAT) and visible/near-infrared reflectances (PARASOL) for the estimation of aeolian aerodynamic roughness length in arid and semi-arid regions

2012 ◽  
Vol 5 (2) ◽  
pp. 2933-2957
Author(s):  
C. Prigent ◽  
C. Jiménez ◽  
J. Catherinot
Keyword(s):  
Arid Regions ◽  
Near Infrared ◽  
Roughness Length ◽  
Aerodynamic Roughness Length ◽  
Sources Of Information ◽  
Transport Models ◽  
Dust Transport ◽  
Infrared Observations ◽  
Aerodynamic Roughness ◽  
Semi Arid

Abstract. Previous studies examined the possibility to estimate the aeolian aerodynamic roughness length from satellites, either from visible/near-infrared observations or from microwave backscattering measurements. Here we compare the potential of the two approaches and propose to merge the two sources of information to benefit from their complementary aspects, i.e. the high spatial resolution of the visible/near-infrared (PARASOL part of the A-Train) and the independence from atmospheric contamination of the active microwaves (ASCAT on board MetOp). A global map of the aeolian aerodynamic roughness length at 6 km resolution is derived, for arid and semi-arid regions. It shows very good consistency with the existing information on the properties of these surfaces. The dataset is available to the community, for use in atmospheric dust transport models.

scholarly journals Near-infrared observations of the Fornax dwarf galaxy

2007 ◽  
Vol 467 (3) ◽  
pp. 1025-1036 ◽  
Author(s):  
M. Gullieuszik ◽  
E. V. Held ◽  
L. Rizzi ◽  
I. Saviane ◽  
Y. Momany ◽  
...  
Keyword(s):  
Near Infrared ◽  
Dwarf Galaxy ◽  
Infrared Observations
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