"Ultra‐faint" dwarf galaxies: when size does maer UdR1: INAF – Osservatorio UdR2: INAF – Osservatorio Astronomico di Bologna Astronomico di Capodimonte Gisella Clementini (responsabile) Vincenzo Ripepi (responsabile) Luciana Federici Marcella Marconi Monica Tosi Ilaria Musella Michele Cignoni Massimo Dall’Ora Maria Ida Moretti Giuseppina Coppola Francesca Annibali Alessia Garofalo Ultra-faint Dwarfs Spheroidals galaxies of MW and M31 Milky Way Canes Venatici I Canes Venatici II Hercules Leo IV Leo T Andromeda And V And XI And XII And XIII "Ultra-faint dwarf galaxies": The Milky Way satellites Alessia Garofalo Osservatorio Astronomico di Bologna The dSphs galaxies surronding the Milky Way ''Ultra-faint'' MW dSphs “Bright” MW dSphs Willman I Carina Leo IV Draco LeoV Fornax Coma Leo I Leo T Leo II Bootes I Sculptor Bootes II Sextans Bootes III Ursa Minor Canes Venatici I Sagittarius (Canis Major) Canes Venatici II Hercules Segue I Segue II Leo T Ursa Major I Ursa Major II Belokurov et al.(2007) Pisces I Pisces II The dSphs galaxies surronding the Milky Way ''Ultra-faint'' MW dSphs Willman I Leo IV LeoV Coma Bootes I Bootes II Bootes III Canes Venatici I Canes Venatici II Hercules Segue I Segue II Leo T Ursa Major I Ursa Major II Pisces I Pisces II Four MW UDFs based on WFPC2 HST archive data FOV (HST) 5.7 arcmin² (very central region of UFDs!) The CMDs extend 2.5 mag below the main sequence turn-off Leo IV σV σ (V-I) V ~ 25.5 0.04 0.06 Cvn I V ~ 25.5 0.04 0.07 Cvn II V ~ 24.5 0.04 0.07 Hercules V ~ 25.1 0.03 0.50 Red dots show RR Lyrae stars located in the HST FOV, they trace the HB . Hercules in details... D= 132 kpc Dates Filter Exposure lenght N Total HST data reduction with (sec) Exposure (sec) HSTphot package (Dolphin 2000) February 26 F606W 1200 3 3600 2007 Cross identification of stars F814W 1200 5 6000 beetween HST and ground-based (e.g. WHT+INT+WFI) catalogues INT's FOV HST's FOV Identification of the variable stars UDFs <[Fe/H]> N(RRab/c/d) <Pab> Oo Type • Hercules -2.4 6+3 0.68 Oo II Musella et al. 2011, in preparation Leo T: CMD and light curves obtained from HST WFPC2 archive data... UDFs <[Fe/H]> N(RRab/c/d) <Pab Oo Type > • Leo T -2.1 1 0.60 Oo Int Blue dots ACs/SPCs stars Red dot RRab star ...and SFH! (see Annibali's talk) Ultra-faint dwarf galaxies The Andromeda satellites Giuseppina Coppola INAF Osservatorio Astronomico di Capodimonte The project Context Aims The stellar content of the “ultra-faint” dwarf spheroidal galaxies (UFDs) characterize the stellar recently discovered around M31 (see populations of UFDs and dSph e.g. Martin et al. 2009, ApJ 705, 758) satellites of M31; can provide fundamental insight to derive the early star formation reconstruct the star formation history history; and the merging episodes that led to provide hints on how the M31 the early assembling of the M31 halo. halo has formed Tools Pulsating Variable Stars Color Magnitude Diagrams Pulsating variables trace the different stellar generations in galaxies young (t < 100 Myr) Classical Cepheids, (δ Scuti stars) intermediate age Anomalous Cepheids old (t > 10 Gyr) RR Lyrae, Pop II Cepheids, (SX Phoenicis) Observations and data reduction We are analysing several M31 UFDs and dSphs using HST archive data complemented by time series photometry obtained with the OSIRIS camera at the GRANTECAN, the LBC camera at the LBT, and the DOLORES camera at the TNG. M31 dSphs and UFDs M31 dSphs and UFDs: our HST sample HST M31 dSphs and UFDs: HST + LBT HST LBT M31 dSphs and UFDs: HST + LBT + GTC HST LBT GTC M31 dSphs and UFDs: HST + LBT + GTC +TNG HST LBT GTC TNG M31 dSphs and UFDs: HST + LBT + GTC +TNG HST LBT GTC TNG Data reduction strategy PSF photometry of the time series with: − DAOPHOT/ALLSTAR/ALLFRAME (Stetson 1994) for ground-based obs − HSTPHOT (Dolphin 2000) for HST obs CMDs light curves M31 dSphs and UFDs HST dataset FOV 5.7 arcmin2 And V And XI And XIII And XII M15 NGC6397 M92 M92 Typical errors VTO σV σ(B-V)/(V-I) ≈ 25.5 0.04 0.06 ≈ 27.5 0.18 0.20 RR Lyrae stars in M31 dSphs and UFDs UDFs <[Fe/H]> N(RRab/c/d) <Pab> Oo Type • And V -2.2 >7+3 ??? O??? • And XIII -2.0 12+5 0.66 Oo II • And XI -2.0 in progress • And XII -1.9 in progress And XIII (Contreras et al. 2011) And V (Federici et al. 2011) HST data GTC data The star formation history ! of dwarfs" Francesca Annibali INAF-Osservatorio Astronomico di Bologna" The synthetic CMD method" • Stellar evolution tracks" • Bolometric conversion tables" Monte Carlo" • SF beginning, duration and law" (Mass, Age)" • Metallicity" Interpolate on the tracks" • Reddening" • Initial Mass Function (IMF)" (Log L, log Teff)" • Distance Modulus (DM)" Bolometric corrections" Abs Magnitudes" DM, reddening, phot err" Obs Magnitudes" STOP when " Completeness Retained" N. SIM = N. OBS" Test Rejected" The SFH of LeoT" Leo T (SDSS)" D # 400 kpc" 7 MTO T# 10 M" M/L # 140 M/L LBT data (de Jong et al. 2008)" -3<[Fe/H]<-1.6" The SFH of LeoT" Leo T (SDSS)" D # 400 kpc" 7 MTO T# 10 M" M/L # 140 M/L" LBT data (de Jong et al. 2008)" -3<[Fe/H]<-1.6" WFPC2 data (Clementini et al submitted)" The SFH of LeoTS"imulations by M. Cignoni" Cepheids Leo T (SDSS)" RR Lyrae D # 400 kpc" 7 MTO T# 10 M" M/L # 140 M/L WFPC2 data (Clementini et al submitted)" -3<[Fe/H]<-1.6" The SFH of LeoTS"imulations by M. Cignoni" Cepheids Leo T (SDSS)" RR Lyrae D # 400 kpc" 7 MTO T# 10 M" M/L # 140 M/L" WFPC2 data (Clementini et al submitted)" Comparison with late-type dwarfs: D # 18 Mpc" 8 IZw 18" MTO T# 10 M" －－ (V, I) CMDs" 1/30 Z 1/50 Z 5 My 10 My ACS/WFC data" 20 My FOV: 50” x 50 “ = 4 x 4 kpc2" seondary body" main body" N E Contreras-Ramos et al. 2011" Comparison with late-type dwarfs: D # 18 Mpc" 8 IZw 18" MTO T# 10 M" －－ 1/30 Z 1/50 Z ACS/WFC data" FOV: 50” x 50 “ = 4 x 4 kpc2" seondary body" main body" N E Contreras-Ramos et al. 2011" Comparison with late-type dwarfs: D # 18 Mpc" 8 IZw 18" MTO T# 10 M" －－ 1/30 Z 1/50 Z ACS/WFC data" FOV: 50” x 50 “ = 4 x 4 kpc2" N E Annibali et al. In prep." Summary" Variable stars CMDs/ SFH" •MW UFDs" Canes Venatici I: RR-Lyrae old + int(?)" (HST/WFPC2 +" Canes Venatici II: RR-Lyrae GC like" ground-based data)" Hercules: RR-Lyrae GC like" Leo IV: RR-Lyrae GC like" Leo T: RR-Lyrae + Cepheids old + int + young " •M31 And V: RR-Lyrae GC like " And XI: RR-Lyrae GC like " satellites" And XII: in progress GC like" (HST/WFPC2 +" And XIII: in progress GC like" ground-based data)" •Compare with e.g. IZw18, in progress other metal-poor dwarfs".