Rosaria (Sara) Bonito

Dipartimento di Fisica e ChimicaUniversita' degli Studi di Palermo

INAF-Osservatorio Astronomico di Palermo

THE PROBLEMS OF SKY SUBTRACTION

AND OF ANOMALOUS MEMBERS IN YOUNG CLUSTERS:

THE CASE OF NGC 6611

FLAMES observations (HR15N setup)

NGC 6611: forthcoming observations

GES

NGC 6611 & GES

(Bonito et al. 2013)

Nebular contribution to Ha emission Strongly varying in space and time Narrower than stellar

FWZI method (as EW and Ha10% cannot be derived)

SKY SUBTRACTION & Ha

FWZI METHOD (1) Zoom +/- 3 A around Ha in sky spectra

FWZI METHOD (2) Normalize: spectrum without the emission line

FWZI METHOD (3) Difference or ratio original

spectrum/spectrum without the emission line

FWZI(Ha) skyFWZI METHOD (4)

< 3 A

FWZI(Ha) star >> FWZI(Ha) sky

FWZI(Halpha) & ACCRETION (Bonito et al. 2013)

Upper limit for EW(Li) using other features in the Li spectral region (Randich et al. 2009)

Median sky subtraction (Jeffries & Oliveira 2005)

SKY SUBTRACTION AND Li (1)

Spurious absorption lines due to [SII] 6717 A

SKY SUBTRACTION AND Li (1)

SKY SUBTRACTION AND Li (2)

No Li No veiling

Age Membership

NGC 6611: forthcoming observations g Vel NGC 2264 NGC 6530

IMPLICATION FOR GES

BWE STARS IN NGC 6611 (Bonito et al. 2013)

+: members from the Guarcello et al. (2010) catalog

: all the targets observed with FLAMES

: BWE stars (with disk)

BWE STARS: WHY?

> 50 %: members(Bonito et al. 2013)

old members? (De Marchi, Panagia, Guarcello, Bonito et al. 2013)

also in other clusters

completeness

age spread?

GES

CONCLUSIONS Sky subtraction FWZI(Ha) method Spurious absorption lines (Li)

Blue with excesses (BWE) stars completeness age spread other clusters (GES)