TRGB ..

I.

Sextans A, KPNO 2m telescope

, , . PSF- : DAOPHOT II (Stetson 1987), DoPHOT (Mateo, Schechter 1989), DOLPHOT(Dolphin 2000) , , ,

MS ( ), 10-300 Myr BL ( He ), 10-300 Myr RSG ( He ), 10-300 Myr AGB , > 1 Gyr RGB ( He ), > 1 Gyr RC

Lee et al. (1993)

Lee et al. (1993) , M(I) = -4.0, I(TRGB) 0.1-0.2 magSakai et al. (1996) LF TRGB Mendez et al.(2002), 0.05 mag Makarov et al.(2006), 0.02 mag

KK197 dSph DDO165 dIrr HST/ACS (F814W) HST/WFPC2(F606W)

- KK197 (d=3.9 Mpc) Z=0.001 Girardi et al. (2000)

- DDO 165 (d=3.7 Mpc)

: 1. CMD RGB

: 2. RGB/AGB ITRGB

DDO 165ITRGB= 24.40.1 mag

: 3. 0 = m0,I - MITRGB

m0,I = ITRGB - AI

MITRGB = -4.050.12,

AI -

0 = 25+5 lg d (Mpc)

: 4. 1. : I,TRGB2 = phot2+aper2+zero2+AI2 aper = 0.05 mag zero = 0.05 mag AI - 16% (Schlegel et al. 1998)

2. : MI,TRGB = 0.12 mag (Bellazzini et al. 2001)

3. : res2 = I,TRGB2 + MI,TRGB2

4. :dist2 = d res2/2.17

II. . . .

v = H0d v - , d - Mpc, H0 -

H0 = 70 75 km/s/Mpc

vLG= H0d: ..

: 10 : V (mag), error V (mag), I (mag), error I (mag)VLG , , NED , kk NED [kk98] local_volume

- RGB TRGB

Lee M. et al. 1993, ApJ, 417, 553 Sakai S. et al. 1996, ApJ, 461, 713Bellazzini et al. 2001, ApJ, 556, 635Mendez et al. 2002, AJ, 124, 213Makarov et al. 2006, AJ, 132, 2729A. Dolphin 2000, AJ, 531, 804Stetson P. 1987, PASP, 99, 191Schlegel et al. 1998, ApJ, 500, 525Rizzi et al. 2007, ApJ, 661, 815