GALAXIES IN THE FIELD OF THE GAMMA-RAY BURST

GRB 021004I.V. Sokolov, Yu.V. Baryshev, T.A. Fatkhullin

Results (counts of galaxies, photometric red shifts, etc.) of BVRI observations of the field of size 4'.3 x 4'.3 with the host galaxy of the gamma-ray burst GRB 021004 are presented. Observations were carried out with the BTA/SCORPIO. The catalog of galaxies found in this field includes 261 objects with the signal/noise ratio more than 4 in each filter. This restriction defines the following values of the limit stellar magnitudes: 26.0 (B), 25.5 (V), 25.0 (R), 24.5 (I). The exposure times were 3600s (B), 3600s (V), 2700s (R), 1800s (I). Photometric red shifts of these galaxies up to z ~ 3.5 were determined.

The field of the host galaxy of the gamma-ray burst GRB 021004 was observed photometrically with the 6-meter telescope of SAO RAS on November 30 and December 1, 2002. Conditions of observations were photometric; the image quality of 1.3" was measured as the full width at half maximum (FWHM) of the image of stellar-like objects in the field. The coordinates of the host galaxy are ; α2000.0 = 0h26m54s.4, δ2000.0 = 18°3'44".42, which corresponds to the galactic latitude and longitude b = - 43°5'37".1, l = 114°4'34".3. Observations were carried out with the device SCORPIO mounted in the primary focus of the 6-meter telescope of SAO RAS. The CCD TK1024 of size 1024x1024 was used as the light detector. The size of an element of resolution is 24 microns, which corresponds to the angular scale of 0".289 per element. The CCD sensitivity curve and wideband filters set in SCORPIO implement a photometric system close to the standard Johnson-Cousins BVRI system (Bessel, 1990).

The BVRI fields of the host galaxy of GRB 021004 with the exposure times. In the B image 311 detected objects (S/N>3) are marked: extended objects are in blue, stellar-like objects are in red, the cross marks the host galaxy.

Texp = 3600 s Texp = 3600 s

Texp = 2700 s Texp = 1800 s

Diagrams “Stellar magnitude - color” for objects with S/N>3.

Two-color diagrams of objects (S/N>3) detected in the 4 filters.

Two-color diagrams of stellar-like objects.

Differential and integral counts of objects with S/N>3

Differential and integral counts of objects with S/N>3

Differential and integral counts of objects with S/N>3

Diagrams "St.magn. - HyperZ photometrical redshift". The Seaton (MW) extinction law was used.

The Hubble diagram for host galaxies and BTA-field galaxies of GRB 021004 and GRB 000926. Vertical bars are typical errors of estimations of photometric z. Filled squares are for BTA data of host galaxies. Filled circles are for data from the telescopes Keck, VLT and HST. Empty squares are for galaxies with power-law continuum.

Гистограмма z