John Menzies SAAO
dsph in Local Group Local Group associated with Galaxy, M31, within ~1 Mpc of centre of mass Galaxy has 25 companion dsph M31 has ~ 26 ~ 3 dsph not associated with either, near boundary dsph have relatively small mass in stars < 25x10 6 M Θ Contribute to construction of large galaxies (eg, Sgr dsph) Little or no current star formation July 2014 Vienna 2
AGB stars Brightest stars bolometrically in dsph, particularly prominent in NIR Post RGB evolutionary stage, undergoing mass loss to varying degrees (up to ~ fewx10-5 M Θ /yr) contribute significantly to ISM and later generation of stars most in dsph appear to be C stars, many are variable July 2014 Vienna 3
Photometric monitoring in J,H,K S of brightest accessible dsph with IRSF at SAAO, Sutherland Search for Variability in particular Patricia Whitelock, Michael Feast, Noriyuki Matsunaga and other Japanese colleagues July 2014 Vienna 4
Fornax Most massive MW dsph Extended SFH (deboer et al,2013,a&a,544,73) [M/H] range -0.6 to -2 Peak at -0.9 (Gullieuszik et al 2007) CM diagram: RGB with diagonal TRGB Numerous AGB stars extend to v red J-K SR variables, Miras Iscohrones 2Gyr, 10Gyr, [M/H] ~ -0.9 Whitelock P A et al. MNRAS 2009;394:795-809 July 2014 Vienna 5
Spectral types available for many stars C,S,M Shown on CM diagram and 2-colour diagram Extreme (H-K) colours cf LMC C stars Thick dust shells Dust mass-loss rate ~5x10-9 M Θ /yr (Lagadec et al 2008) Whitelock P A et al. MNRAS 2009;394:795-809 July 2014 Vienna 6
Stars with J-K S > 1.0 appear to be variable Typically 18 epochs of observation Std dev a measure of variability Amplitude increases towards redder colours (red points variables from optical (Bersier&Wood (2002)) Whitelock P A et al. MNRAS 2009;394:795-809 July 2014 Vienna 7
Variables SR Miras Non-periodic Whitelock P A et al. MNRAS 2009;394:795-809 July 2014 Vienna 8
Leo I Low-level star formation over a long period with a burst from 1-3 Gyr ago (Dolphin 2002) Very narrow distribution of [M/H], peaking at -1.2 (Gullieuszik et al 2002) CM diagram shows a well-populated AGB above a narrow RGB TRGB K S = 16.14 AGB has C stars, SR and Mira variables Isochrones for 10Gyr and 2 Gyr with typical metallicity Menzies J W et al. MNRAS 2010;406:86-94 July 2014 Vienna 9
Two colour diagram for Leo I 2 colour diagram shows reddest stars significantly redder than LMC Dust shells Menzies J W et al. MNRAS 2010;406:86-94
Menzies et al 2002: 4 extremely red variables, positions but no periods determined we have not been able to find any relationship whatsoever between those coordinates and reality Held E V et al. MNRAS 2010;404:1475-1489 July 2014 Vienna 11
V image K image Held E V et al. MNRAS 2010;404:1475-1489 July 2014 Vienna 12
Miras Long-term trends Menzies J W et al. MNRAS 2010;406:86-94 Vienna 13
Sculptor Predominantly old population (deboer et al 2012) Some evidence of ~2Gyr population (Revaz et al 2009 Range of [Fe/H], -1 to -2, mean -1.58 (Kirby et al 2009), tail to ~-3.0 CM diagram shows little AGB 2 Miras, 6 C stars below TRGB 3 v low metallicity Menzies J W et al. MNRAS 2011;414:3492-3500 July 2014 Vienna 14
C stars below TRGB Young, relatively metalrich? Isochrone 2Gyr [Fe/H]~-1.1 C/O >1 in black (Marigo et al 2008) Or extrinsic? Not variable Menzies J W et al. MNRAS 2011;414:3492-3500 July 2014 Vienna 15
Two-colour diagram for Sculptor MAG29 and V544 periods 554 and 189 d Mira MAG29 significantly red wrt LMC Period 554d suggests it is young Menzies J W et al. MNRAS 2011;414:3492-3500
Sextans Very similar optical CM diagram to Sculptor Mean [Fe/H] = -1.9 (Lee et al 2009) 2 extremely metal-poor stars [Fe/H]<-3 2 Miras (Sakamoto et al 2012) periods 122 and 326 days longer period one is a C star(mauron et al 2004) Matsunaga, priv comm July 2014 Vienna 17
Carina Complex SFH, episodic Most stars formed in 2-6 Gyr episode, [Fe/H] -1.8 to -1.2 Old population >10Gyr [Fe/H]<-1.5 Unpublished CM diagram Field stars, RV members 9 C stars, 3 below TRGB, 3+ variable July 2014 Vienna 18
Leo II Predominantly old population ~9 Gyr (±2). Small intermediate age population (C stars) Low metallicity, mean [Fe/H] ~-1.7, some -1.1 CM diagram shows only C stars Above TRGB, one below One Mira, P=183d Gullieuszik M et al. MNRAS 2008;388:1185-1197
Others in MW System Draco, Ursa Minor Old, similar SFH Carbon stars, at or below TRGB No LPV variable search Cetus, Tucana Tucana 2 old populations, different metallicities 7 possible LPV (@TRGB), No C stars Cetus Old population 1 possible LPV, 6 C stars, 3 below TRGB July 2014 Vienna 20
Sgr dsph Predominantly ~8 Gyr [Fe/H] -0.4 to -0.7 Some -0.25, some -2.0 Early NIR work selected from 2MASS (Whitelock et al 1999) 26 spectroscopic C stars; estimate total ~100 8 Miras Evidence for intermediate age population Lagadec et al 2009 6 C-rich stars, all Miras Batinelli & Demers 2013 Choose probable C stars (J-K) 0 >1.4 from 2MASS 12 new Miras + 13 other red variables McDonald et al 2012 Spectroscopically identified 5 S stars, 19 new C stars McDonald et al 2014 31 reddened AGB stars (J-K)>1.3, 21 LPV, no periods July 2014 Vienna 21
Galaxy Mass* M V * [Fe/H] * C stars Miras x10 6 M Θ Sgr dsph 21-13.5-0.4 51+ 26+ Fornax 20-13.4-0.99 104 7 Leo I 5.5-12.0-1.43 26 7 Cetus 2.6-11.2-1.9 3 (3)? Sculptor 2.3-11.1-1.72 2 (6) 2 Antlia 1.3-10.4-1.6?? Leo II 0.74-9.8-1.62 8 1 Tucana 0.56-9.5-1.95 0? Sextans 0.44-9.3-1.93 2 2 Carina 0.38-9.1-1.72 6 (3) 0 Draco 0.29-8.8-1.93 (6) 0 U Mi 0.29-8.8-2.13 (7) 0 *McConnachie 2012 July 2014 Vienna 22
Mira Variables Distance Indicators Apart from Sgr dsph, dsph have 19 Miras. Same K-logP in LMC for both O- and C stars (Whitelock et al 2008) Also fits dsph Miras but effects of dust shells evident in some dsph Miras Bolometric corrections based on (J-K) colours (Whitelock et al 2006) M bol logp relation fits very well Important to use BC consistently As useful as Cepheids in infrared (Feast & Whitelock 2013) Both 50d Cep and 380d Mira have M K ~ -7.9 At 8μm, 50d Cep and 230d Mira: M 8 ~ -8.3; 380d Mira: M 8 ~-9.2 July 2014 Vienna 23
July 2014 Vienna 24
Galaxy Mass* M V * [Fe/H]* C stars Miras x10 6 M Θ And VII 9.5-12.6-1.4 3 (2)? And II 7.6-12.4-1.64 2 (1)? And I 3.9-11.7-1.78 0? And VI 2.8-11.3-1.3 1 (1)? And III 0.83-10.0-1.78 (1)? And V 0.39-9.1-1.6 0? And X XXIX <~1-10 - - 6.5-1.5 - - 2.3?? *McConnachie 2012 July 2014 Vienna 25