Estimation of photometric distances for NOMAD stars

1
Estimation of photometric distances for NOMAD
stars


Supervisor PhD, Alexander S. Tsvetkov
Alexey A. Smirnov

• Mathematics Mechanics dept.,
• SPbSU, 2009.

2
NOMAD superiority
NOMAD (Naval Observatory Merged Astrometric
Dataset), contains 1 117 612 732 stars, from
catalogues Hipparcos UCAC2 (gt10m)
Tycho-2 USNO-B 2MASS. Total volume 92
Gb! Catalogue includes positions, proper
motions and their errors six-band
photometry cross-identity data.
3
NOMAD photometry
About 243 millions of stars have photometry in
all bands.
4
NOMAD number of stars against visual mag.
5
NOMAD disadvantages

• Not good proper motions
• 2. Artifacts are about
• 2.3 of all catalogue.
• 3. No distances!

6
Conception of Distance determination
Six-band photometry
Spectral classification
Photometric distances
7
Auto classification of stars by multiband
photometry
19621965 Vilnius multiband photometry system
(UPXYZVH) with a goal to provide full auto
spectral classification. (Strajys V. et. al.)
BVRJHK system doesnt allow 100 classify any
star (temperature and luminosity classes). The
main goal is to establish classification of stars
of NOMAD that have six band photometry.
8
Normal color indexes
Normal index means that the stars we use are in
100 pc radius where the interstellar extinction
is small (all but). NOMAD photometry allows to
compute the next color indexes for 243 millions
of stars BV VR VJ VH VK And we
can compare this color indexes with normal color
indexes.
9
Computing normal color indexes
We compiled next catalogue base Hipparcos
Sp. classification from Tycho-2 Spectral
Type BVRJHK bands from NOMAD
Distances limit 100 pc.
B2M8 stars, III and V luminosity classes.
10
Normal color index temperature class diagrams
11
B-V T_class
12
V-R T_class
13
V-J T_class
14
V-H T_class
15
V-Ks T_class
16
Temperature class detection
We have no big difference between dwarfs and
giants branches. Average it! Now, we can detect
temperature class (simple bijective mapping).
17
Luminosity class detection
18
Spectral classifications accuracies
Accuracies checking of the catalogue HIPPARCOS
Tycho-2 Sp.t.NOMADphotometry. Accuracy
of temperature class lt 0.3 temp.
class luminosity class depends on star
reddening.
19
Tycho-2 Sp.t. stars distribution
20
NOMAD six-band photometry stars distribution
21
Detection of luminosity class from temperature
class
22
Distance computing
2d spectral classification
Photometric distances
Interstellar extinction
If rsp gt 1 kpc Av 0
23
NOMAD distances
Distances for 243 000 000 stars!
24
NOMAD, G stars
25
NOMAD, M stars
26
In result
The catalogue of spectral classifications and
photometric distances for 243 millions of NOMAD
stars is constructed.
27
Conclusion

• We have no facilities to compute some excellent
  distances for NOMAD objects.
• But we can do estimations of spectral
  classification
• Good detecting of temperature class
• (accuracy is about 0.3 temperature class)
• Satisfactorily detection of luminosity class.

28
Applications
Detection of stellar clusters spectral
consistence, this is very important
for history of cluster evolution kinematics
and distances.
29
Thank you
You can contact with me by e-mail
alsmirn_at_gmail.com