The Cepheid distance to the LMC from the first results of the VISTA Magellanic Cloud (VMC) Survey.

Transcription

1 The Cepheid distance to the LMC from the first results of the VISTA Magellanic Cloud (VMC) Survey. Vincenzo Ripepi Marcella Marconi Maria Ida Moretti Gisella Clementini Maria Rosa Cioni INAF-Osservatorio Astronomico Capodimonte - Italy INAF-Osservatorio Astronomico Capodimonte - Italy INAF-Osservatorio Astronomico di Bologna - Italy INAF-Osservatorio Astronomico di Bologna - Italy Univ. of Hertfordshire, UK & Univ. Observatory Munich, Germany & the VMC team

2 The VMC Survey VMC is an ESO public survey (P.I. M.R. Cioni, see Cioni et al. 2011, A&A, 527, 116) The most sensitive near-infrared survey of the Magellanic Cloud (MC) system Total surveyed area ~ 180 deg 2 (LMC = 116 deg 2 ; SMC = 45 deg 2 ; Bridge = 20 deg 2 ) Specifically designed to have a good sampling of RR Lyrae and Cepheid light curves Started on October 2010 (present completion ~ 11%)

3 VMC Survey: observations Observa)ons in YJKs with 4 m (Paranal, Chile) Data reduc)on with the VISTA Data Flow System (VDFS) pipeline at CASU (Cambridge Astronomical Survey Unit) Catalogues handling through the Vista Science Archive (VSA) Cioni et al. (2011) Cioni et al. (2011) 1 Tile = º x º 1.5

4 The VMC Survey: Science I. Spa)ally resolved SFH II. 3D structure (variable stars, red clump, ) III. The distance to the LMC IV. Stellar sub structures (clusters, streams ) V. PNe, SNRs and other extended sources (galaxies) VI. Differen)al proper mo)on VII.Star forma)on VIII.Tes)ng models of the Magellanic Clouds evolu)on IX. Ex)nc)on maps X.

5 Cepheids in the NIR Low-amplitude light curves Low dependence on reddening PL in J and K linear Low dependence on metallicity Low dispersion (< 0.1 mag) Madore & Freedman (1991) Persson et al. (2004) Caputo, Marconi, Musella 2000 A&A

6 Wesenheit relations W(K,VK)=K-0.13(V-K)=αlogP+β Reddening independent Low metallicity dependence Very low dispersion Ideal for tracing the 3D structure of the MCs Caputo et al Persson et al. 2004

7 VMC Survey: RR Lyrae stars and Cepheids Optical data from EROS II B,R ( V,I) light curves for ( 16000) RR Lyrae stars and( 5800) Cepheids in the LMC (kindly made available to us by J.B. Marquette) OGLE III V,I light-curves and accurate variable star classification in the LMC (3375 Classical Cepheids and RR Lyrae) and SMC (4630 Classical Cepheids and 2475 RR Lyrae) Only two fields completed so far: Gaia field (South Ecliptic Pole test field) Moretti et al. Poster, this conference) 12 Cepheids; 111 RR Lyrae stars ( see 30 Dor region 320 Cepheids and 700 RR Lyrae stars

8 Gaia Field EROS 2 RR Lyrae distribution in LMC; courtesy J.B. Marquette and M.I. Moretti

9 30 Dor Field VMC three color image EROS 2 Cepheid distribution in LMC; courtesy J.B. Marquette and M.I. Moretti

10 Cepheid Light Curves GAIA Field: 4 F 8 FO 30 Dor Field: 161 F 8 F/FO 139 FO 15 FO/SO

11 Results: PLK in 30 Dor

12 Results: PLK and W(K,VK) in 30 Dor Strong differential reddening makes the use of the W(V,K) relation more appropriate.

13 Results: W(V,K) in 30 Dor W(K,VK)F=(-3.260±0.028)logP +(15.830±0.019) rms=0.070 mag W(K,VK)FO=(-3.530±0.025)logP +(15.400±0.008) rms=0.071 mag

14 W(V,K) in 30 Dor: comparison with the literature Persson et al. (2004) sample W(K,VK)F=(-3.359±0.034)logP +(15.91±0.043) rms=0.088 mag 30 Dor sample W(K,VK)F=(-3.260±0.028)logP +(15.830±0.019) rms=0.070 mag Caputo et al. 2000

15 W(V,K) in 30 Dor and LMC sample Persson et al. (2004) sample W(K,VK)F=(-3.359±0.034)logP +(15.91±0.043) rms=0.088 mag 30 Dor sample W(K,VK)F=(-3.260±0.028)logP +(15.830±0.019) rms=0.070 mag

16 W(V,K) in 30 Dor and LMC sample Persson et al. (2004) sample W(K,VK)F=(-3.359±0.034)logP +(15.91±0.043) rms=0.088 mag 30 Dor sample W(K,VK)F=(-3.260±0.028)logP +(15.830±0.019) rms=0.070 mag Joint samples: W(K,VK)F=(-3.325±0.014)logP +(15.87±0.013) rms=0.078 mag

17 W(V,K) in 30 Dor and Gaia fields Perhaps we are observing stars located at different distances from the LMC center

18 W(V,K): Galactic Cepheids with Trig. Parallaxes Trigonometric parallaxes by Benedict et al. (2007) and van Leeuwen et al. (2007) Lutz-Kelker correction by Benedict et al. (2002). LSQ: W(K,VK)F=(-3.28±0.14)logP- (2.61±0.12) rms=0.10 mag LMC slope imposed: W(K,VK)F=-3.325logP-(2.57±0.03) (m-m)0=18.44±0.08 mag

19 W(K,VK) in NCG 1866 Using: Ks-band photometry for NGC 1866 by Storm et al. (2004), Testa et al. (2007); UBVI proprietary data Molinaro et al. (Poster this conference) applied a modified version of the CORS Baade-Wesselink method to 9 cepheids in NGC 1866, deriving (m-m)0=18.56±0.03 mag (random error). (m-m)0=18.54±0.08±sist. mag HV12204

20 Distance to the 30 Dor Field (LMC) from the W(K,VK) Calibrators Method (m-m)0 Dispersion Caputo et al. (2000) Theory 18,69 0,10 Benedict et al. (2007) van Leeuwen et al. (2007) Trigonometric parallaxes 18,44 0,08 Fouque et al. (2007) Various Galactic 18,42 0,08 Gieren et al. (2005) LMC Cep. ISBM 18,43 0,09 Molinaro et al. B-W NGC ,54 0,08 AVERAGE 18,46 0,06

21 Distance to 30 Dor Field (LMC) from W(K,VK) After Clementini et al. (2003)

22 Conclusions VMC survey is going on First results on the Gaia and 30 Dor fields Nice light curves for all pulsating variables, in particular Classical Cepheids and RR Lyrae stars W(K,VK) low dispersion good 3D tracer Using different calibrations we find: (m-m)0[30 Dor]=18.46±0.06 waiting for GAIA direct distance measure of LMC Cepheids