Instituto de Astrofìsica de Canarias Photometric and spectroscopic properties of stellar populations in the Carina dSph galxy M. Monelli Instituto de Astrofìsica de Canarias Concepcion, Jan 8-14, 2007
dSph/dE dSph/dIrr dIrr Spirals S. Hidalgo
An example: the field of IC1613 Rt~15' ACS
An example: the field of IC1613 Rt~15' I. Drozdovski ACS + Subaru
An example: the field of IC1613 Rt~15' ACS + Subaru CFHT
(m-M)0 D(Kpc) Mv (TO) Rcore (') Rtidal (') Galaxy satellites 18.5-22 50-250 22.5-26 6-16 10-80(?) M31 satellites 23.5-24.5 500-800 27-28.5 <3 5-17 Isolated <26 <1600 <30 <5 North telescope Mirror (m) Obs type F.o.v. SuprimeCam SUBARU 8 Imaging 30'x24' PrimeFocus WHT 4.2 16'x16' MegaCam CFHT 3.6 1°x1° WFC INT 2.5 34'x34' South VIMOS VLT Ima/spec 16'x18' MOSAICII CTIO 4 36'x36' WFI 2.2 ESO 2.2 33'x34' FORS1/2 7'x7' FLAMES Spec 25'x25' ACS HST 2.4 imaging 3'x3'
TO star, Mv~3.5 D~200Kpc, (m-M)=21.5 mv(TO)~25 D~2Mpc, (m-M)=26.5 mv(TO)~30 D~770Kpc, (m-M)=24.5 mv(TO)~28 S. Hidalgo
Use different approaches! 4m telescopes + wide-field imagers 8m telescopes + medium-field cameras HST + spectroscopy (8m + multi-object spect.) Global understanding of the properties of nearby galaxies (SFH, variables, radial gradients, tidal interactions…)
WIDE FIELD OBSERVATIONS!! Carina: Observational issues 1°x1° DSS Extended low surface brightness low central density (m-M)0 ~ 20.15 D ~ 100 Kpc Mv ~ -9.3 Rcore ~ 9 Rtidal ~ 29 (47’) (Mateo 1998) WIDE FIELD OBSERVATIONS!!
Why Carina? complex star formation history (Smecker-Hane et al. 1996) ( mix of stellar populations) recent episode (<1Gyr) (Monelli et al. 2003) sizable sample of variable stars (Dall’Ora et al. 2003) high M/L ( ~30 M☼ /L☼) DM? controversial evidence of extra-tidal stars: tidal interactions with the Galaxy or extended halo ? (Hayashi et al 2003, Kazantzidis et al 2004, Monelli et al. 2004, Munoz et al. 2006)
The Carina Project: Long term photometric and spetroscopic project aimed at studying the stellar content of the Carina dSph galaxy G. Bono, R. Buonanno, V. Castellani, C.E. Corsi, F. Caputo, L. Pulone (INAF-Rome Obs.) A.R. Walker (CTIO) M. Dall’Ora, V. Ripepi (INAF-Capodimonte Obs.) A. Munteanu (Univ. Pompeu Fabra) P.B. Stetson (DAO) H.A Smith (MSU) A. Aparicio, C. Gallart (IAC) M. Nonino (INAF-Trieste) F. Thévenin (Nice Obs.) P. Francois (Paris Obs.)
CAREFUL WITH THE CALIBRATION!! The data set: central region Instr. f.o.v. Filter Tot.exp. Date 2.2m ESO 32x33 60 B 30,500s 5-7 Jan 2000 0.23/px 63 V 30,300s + archive CTIO 4m 36x36 54 B 21,200s 19 Dec 1999 0.27/px 54 V 13,000s 8-9 Jan 2000 22 U 22,000s Dec 2004 19 I 5,700s Jan 2005 Photometric reduction with DAOPHOTII/ALLFRAME (Stetson 1987, 1994) ~2,900 frames CAREFUL WITH THE CALIBRATION!! WARNING!!!
Results: color-magnitude diagram ~30000 stars (|sharp|<0.2) DM = 20.24 E(B-V) = 0.03 Z = 0.004 [Fe/H] = -1.7 isochrones superposition: Old population ~11Gyr Intermediate pop. ~3-7 Gyr Young pop ~0.6-1 Gyr
Results: spatial distribution The intermediate-age stellar population is more concentrated toward the centre; old stars are distributed in a sort of diffused halo. The peak of the distribution of the old stars is offset by ~2´.
Spectroscopic data sets GIRAFFE RA DEC λ(nm) exp time (hr) tot # stars 1 06:41:37 -50:57:58 LR8 820-940 (CaT) R~6500 18 ESO archive 1100 (RGB, AGB + field) 2 06:41:00 -50:45:06 15 3 06:42:51 -50:52:50 10 4 06:39:50 -51:04:00 7.5 5 06:42:05 -51:10:00 16 FORS2 A 06:42:03 -50:54:00 1028z (CaT) 773-930 2.6 330 (RGB,HB,MS, TO, variables + field) - 1400V 456-586 (Mg triplet) R~2000 2.9 B 06:42:00 -50:50:30 C 06:41:38 -50:55:34 D 06:41:26 -51:57:30 E 06:40:51 -51:07:56 1.3
Complementary samples FLAMES (archive): based on EIS photometry (Koch et al. 2006) FORS2: based on our photometry Complementary samples
Two main questions: 1) Do the different populations present different kinematical properties? 2) Is there any spread in the chemical composition among different populations?
WARNING!! FLAMES: Uncertainties in sky subtraction: partially masked in the vr determination but show up with the individual abundance determination FORS2: day/night mask positioning abundances Centroid positioning in the slit vr
Work in progress… Different peak?? Hidden systematics?? FLAMES (1095) FORS2 (150) Work in progress… Different peak?? Hidden systematics??
Variable Stars Multiple stellar populations different families of variable stars present in the same system, both in H- and He-burning phases Bright variables as tracers of stellar populations
19 Anomalous Cepheids
79 RRLyrae 19 Anomalous Cepheids
13 binaries 79 RRLyrae 19 Anomalous Cepheids
270 candidates/unclassified 13 binaries 79 RRLyrae 19 Anomalous Cepheids
Outer fields: tidal tails? We observed selected regions around Carina. Deep images were collected in order to use Main Sequence stars as tracers of the stellar content. C, D 30' B 52' E 60' A 1.5 ˚ α, β 2˚ γ 4.5˚ CTIO 4m 2.2m ESO
Conclusions USE DIFFERENT APPROACHES!!