VIMOS@VLT observations of Dolidze 25

Vincenzo Ripepi INAF-Osservatorio Astronomico di Capodimonte, Naples, Italy Collaborators: J.M. Alcalá, F.Cusano, M. Marconi (INAF-OAC) LOI partecipants-PMS collaboration EGBW VIMOS@VLT observations of Dolidze 25

Motivation Primary interest the search for PMS  Scuti candidates for COROT  Interest for young open cluster (age < 10 Myr) in the vicinity of COROT Primary targets, i.e. observed in any case in the EXO field.

Dolidze 25: Properties • Dolidze 25 is a young cluster associated with the HII region S284 • it is far (heliocentric distance > 5.5 Kpc) • it is metal poor: Lennon et al. 1990 found that Dolidze 25 is deficient in metals approximately by a factor 6  somewhat in disagreement with respect to the expected abundance gradient of the disc. • Dolidze 25 could be connected with the Canis Major Dwarf Galaxy which is supposed to be merging with our Galaxy • Dolidze 25 is poorly studies as a SFR. Due to the low metallicity, it represent an ideal object to study matal deficient PMS objects, which would be the counterpart of “normal” TTauri and intermediate mass PMS. • Spectral classification (using spectra) for a relevant number of stars  useful for characterize stars in the exo field.

Galactic model by Cignoni & Degl’Innocenti, Private Comm. Observations: Imaging • Observations in RI with VIMOS@VLT (pre-Imaging data) • Data reduction using psf photometry DAOPHOT/ALLSTAR (Stetson 1987) • Accurate photometric calibrations using Stetson’s extension of Landolt (1992) standards. • Pre-Imaging (+2MASS data+EGBW data) used to select targets for the spectroscopy. High priority to objects showing IR excess.

Observations:multiobject spectroscopy • Medium Resolution: 2.5 Å/pixel (spectral reange 5050-8700 Å)  up to 50 slits per CCD, i.e up to 200 per exposure • High Resolution Red: 0.6 Å/pixel (spectral reange 6350-7500 Å)  > 40 slits per CCD, i.e up to 170 per exposure •  • ~ 900 spectra with MR grism  spectral classification • ~ 550 spectra with HR_red grism  study of PMS stars (if any!) • Preliminary data reduction with ESO VIMOS pipeline (but no defringing, bad sky subtraction for HR and strange features in Q3 for MR) • 100% MR spectra extracted • 50% HR spectra extracted

Results: the HR diagram

Results: spectra

Conclusions and future actions • Dolidze 25 show a rich population of H emission young stars • A few objects are PMS intermediate mass candidates. Four stars fall within the instability strip for PMS  Scuti pulsation • faint objects: but for R~16.5 mag we should be able to do asteroseismology for PMS  Scuti candidates • no problem to study mid/long term variations (UX Ori like) • Several brightKM stars with (and without) Hemission In the future we plan to: • reduce better the data + calibration in flux • obtain spectral classification for all the stars • study membership (UCAC2) • time series photometry for interesting objects – not easy, faint objects • Preparation of proposal in the AP context asking for a few windows in the EXO field. • PMS collaboration • Open to everybody: if you are interested please contact me: • ripepi@na.astro.it

VIMOS@VLT observations of Dolidze 25