Trigonometric parallax Galactic structure Y'Xu M'J'Reid X'W'Zheng K'M'Menten - PowerPoint PPT Presentation

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Trigonometric parallax Galactic structure Y'Xu M'J'Reid X'W'Zheng K'M'Menten

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Structure and dynamics of the Galaxy. Distribution of Dark Matter ... Milky Way as a meter stick. Extragalactic distance. Hubble constant, age of Universe ... – PowerPoint PPT presentation

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Title: Trigonometric parallax Galactic structure Y'Xu M'J'Reid X'W'Zheng K'M'Menten


1
Trigonometric parallax --- Galactic structure
Y.Xu M.J.Reid X.W.Zheng K.M.Menten
Observe gt 10 massive star forming regions
Trigonometric parallax---absolute distance
?Distance-scale calibration
2
What we can do
Structure and dynamics of the Galaxy
Distribution of Dark Matter ----estimate of our
galaxy mass
Disk and outflows in star forming regions
3
Physical mechanism of masers
Precise calibration of other methods ---
absolute magnitude ? ages of globular
Milky Way as a meter stick ? Extragalactic
distance
? Hubble constant, age of Universe
4
Reason of using SFR is
SFR maser is enough to bright, Can observe all
region of galaxy, and origin of maser is
interstellar gases ----which is almost on
galactic plane.
5
Reason of using methanol maser
  • For SiO
  • The bright source is near the sun.
  • Far source from sun is too weak to observe.

For OH not archive enough accuracy and high
special resolution. Each spot is too broad to
determine the position of maser system.
For H2O Short lifetime
6
Background sources
12 GHz methanol maser
Phase referencing
VLBI ? 0.01 mas
  • JVAS (8 GHz)

NVSS (1.4 GHz)? within 0?.7
? VLA ? C- U- band
7
HII regions ? spiral arms of galaxies.
Method used Kinematic distances
  • Rotation curve ?
  • Measure distances to HII regions

8
Construct a plan view of the Milky Way
9
Problems
  • Kinematic distance ambiguities
  • Fish et al. (2003), APJ, 587, 701
  • Non-circular rotation

10
Pilot study ? Perseus Arm----W3OH
  • kinematic distance 4.5 kpc

luminosity distance 2.2 kpc
kinematically anomalous
?
Discrepancy
or
inaccurate for luminosity distance
11
First epoch
Pilot study---(Program BX005)
Five 8-hr tracks
  • Accuracy better than 0.1 mas

When finished 0.05 mas
10 at a distance of 2 kpc
12
Masers in one spectral channel
13
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