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: http://www.sao.ru/precise/Laboratory/Publications/1998/Poor_for_SAO/node1.html
Дата изменения: Fri Mar 5 20:13:59 1999 Дата индексирования: Sat Sep 11 21:07:00 2010 Кодировка: Поисковые слова: annular solar eclipse |
Since their first spectroscopy study (Searle & Sargent 1972) blue compact
galaxies (hereafter BCGs) were classified as evolutionary young systems
due to the fact of their metal content is many times lower than that of
large galaxies. I Zw 18 as the BCG with exceptionally small metallicity
(Z = 1/56 Z)
was even suggested as candidate to local truly young
galaxy forming its first stellar generation. In fact, great majority of
several hundred BCGs with measured
abundance of heavy elements have Z in the range of 1/10 to 1/3 of Z
.
Only a few percent of them have metallicities lower than 1/15 Z
(or 12+log(O/H) < 7.74).
However namely such galaxies are the most interesting from the point of view
the study early chemical evolution of galaxies. Moreover, as demonstrated
recently by Izotov and Thuan (1999), namely BCGs with Z lower than
1/20 Z
are the best candidates to local young galaxies.
Our group during several recent years is involved in the search for and study
of such
extremely low-metallicity galaxies. In the frame of this project such
interesting objects were discovered as SBS 0335-052 (Izotov et
al 1990), 0335-052W (Pustilnik et al. 1997, Lipovetsky et al. 1999) and
HS 0822+3542 (Kniazev et al. 1999) with Z in the range 1/50 to 1/36 of Z,
that is the most metal-deficient galaxies after I Zw 18.
Here we report on the discovery of two
new very low-metallicity BCGs, found in the frame of ongoing project The Hamburg/SAO Survey for Emission-Line galaxies (HSS) (Ugryumov et al. 1999,
Pustilnik et al. 1999). These galaxies are very nearby and comparatively
bright, what makes them very suitable for detailed studies.
Value | 1013+3809 | 1442+4250 |
Right ascention (1950.0) | 10h13m27.6s | 14h42m17.9s |
Declination (1950.0) | +38![]() ![]() ![]() |
+42![]() ![]() ![]() |
Velocity(hel)(km sec-1) | 1198![]() |
780![]() |
Distance (Mpc) | 20.7 | 13.1 |
B-mag | 16.5![]() |
16.0![]() |
MB | -15.1 | -14.6 |
12+log(O/H) | 7.58![]() |
7.68![]() |
Angular size (
![]() |
12![]() ![]() |
60![]() ![]() |
Linear size (kpc) | 1.3![]() |
4.2![]() |
![]() ![]() |
![]() |
Galaxy | |||||
1013+3809 | 1442+4250 | ||||
Ion | F(![]() ![]() |
I(![]() ![]() |
F(![]() ![]() |
I(![]() ![]() |
|
3727 [O II] ..................... | 0.830 ![]() |
0.911 ![]() |
0.649 ![]() |
0.663 ![]() |
|
4101 H![]() |
0.270 ![]() |
0.296 ![]() |
0.191 ![]() |
0.253 ![]() |
|
4340 H![]() |
0.449 ![]() |
0.474 ![]() |
0.425 ![]() |
0.472 ![]() |
|
4363 [O III] ................... | 0.114 ![]() |
0.118 ![]() |
0.123 ![]() |
0.121 ![]() |
|
4861 H![]() |
1.000 ![]() |
1.000 ![]() |
1.000 ![]() |
1.000 ![]() |
|
4959 [O III] ................... | 1.416 ![]() |
1.398 ![]() |
1.734 ![]() |
1.661 ![]() |
|
5007 [O III] ................... | 4.303 ![]() |
4.233 ![]() |
5.076 ![]() |
4.852 ![]() |
|
6563 H![]() |
... | ... | 3.053 ![]() |
2.772 ![]() |
|
Te ............................... | 18000![]() |
16876![]() |
|||
C(H![]() |
0.14 ![]() |
0.09 ![]() |
|||
F(H![]() ![]() |
544 | 186 | |||
EW(H![]() |
117 ![]() |
144.6 ![]() |
|||
EW(abs) Å ................... | 0.65 ![]() |
5.65 ![]() |
|||
z (obs.)........................... | 0.00407![]() |
0.00260![]() |
![]() |