TY - JOUR
T1 - The Gaia-ESO Survey
T2 - A new diagnostic for accretion and outflow activity in the young cluster NGC 2264
AU - Bonito, R.
AU - Prisinzano, L.
AU - Venuti, L.
AU - Damiani, F.
AU - Micela, G.
AU - Sacco, G.
AU - Traven, G.
AU - Biazzo, K.
AU - Sbordone, L.
AU - Masseron, T.
AU - Zwitter, T.
AU - Gonneau, A.
AU - Bayo, A.
AU - Roccatagliata, V.
AU - Randich, S.
AU - Vink, J. S.
AU - Jofre, P.
AU - Flaccomio, E.
AU - Magrini, L.
AU - Carraro, G.
AU - Morbidelli, L.
AU - Frasca, A.
AU - Monaco, L.
AU - Rigliaco, E.
AU - Worley, C.
AU - Hourihane, A.
AU - Gilmore, G.
AU - Franciosini, E.
AU - Lewis, J.
AU - Koposov, S.
N1 - Funding Information:
Acknowledgements. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under program IDs 188.B-3002, 193.B.0936, and 197.B-1074. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the Gaia-ESO Survey Data Archive, prepared and hosted by the WideField Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council. We thank the anonymous referee for their useful comments and suggestions. R.B. would like to thank Dr. Serena Benatti (INAF – Osservatorio Astronomico di Palermo) and Dr. Costanza Argiroffi (University of Palermo – Dept. Of Physics and Chemistry) for their kind help. R. B., L. P., and F. D. acknowledge modest financial contribution from the agreement ASI-INAF n.2017-14.H.O. R. B. acknowledges financial support by PRIN-INAF 2013 Disks, jets and the dawn of planets (PI: Nisini). A. G. acknowledges support from the European Union FP7 programme through ERC grant number 32036 and from the UK space agency. T. Z. acknowledges the financial support from the Slovenian Research Agency (research core funding No. P1-0188). T. M. acknowledges support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant AYA-2017-88254-P. E. R. is supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 664931. L. V. acknowledges support by an appointment to the NASA Postdoctoral Program at the NASA Ames Research Center, administered by Universities Space Research Association under contract with NASA.
Publisher Copyright:
© ESO 2020.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - Context. NGC 2264 is a young cluster whose accretion properties can be investigated in detail by taking advantage of the FLAMES data in the context of the Gaia-ESO Survey. In fact, the analysis of the Hα emission line profile can provide us with information about the accretion and ejection activity of young stars. However, a strong nebular emission that contributes to the Hα emission can alter the profiles, with consequences for their physical interpretation. Aims. Our study is aimed at investigating the accretion and ejection properties of NGC 2264 by applying a proper treatment of the sky contribution to the Hα and forbidden emission lines (FELs; [SII] and [NII] doublets). Methods. We developed a tool, the OHαNA-method, to handle the strong nebular contribution and spectra with spurious profiles of the Hα and FELs, namely altered Hα profiles or absorption features artificially created where emission lines (FELs) are expected. We derived the quantitative measurements of relevant parameters to describe the accretion and ejection processes in young members of NGC 2264, focusing on reliable quantities derived from the width of the lines, which is relatively unaffected by the nebular emission, unlike the intensity peak, which can be altered significantly. Results. We derive the quantitative measurements related to the Hα emission line and discuss the comparison between the original and sky-subtracted spectra. We thus reveal possible profile alterations with consequences for their physical interpretation. Furthermore, we show the analysis of the variability for multi-epoch observations, also deriving the velocity of the infalling and outflowing plasma from the wings of the broad Hα emission line (in accreting stars). We also explore the mass accretion rate versus full width at zero intensity of the Hα line, namely M versus FWZI(Hα), a correlation based on the width of the emission line, which is expected to be more robust with respect to any measurement derived from the peak (e.g., Hα10%) and possibly altered by the nebular contribution. Conclusions. We are able to ascertain that more than 20% of the confirmed accretors, which have already been identified in NGC 2264, are affected by the alteration of their line profiles due to the contribution of the nebular emission. Therefore, this is an important issue to consider when investigating accretion and ejection processes in young stellar clusters. While a small fraction of spectra can be unequivocally classified as either unaffected by nebular emission or dominated by nebular emission, the majority (> 90%) represent intermediate cases whose spectral features have to be investigated in detail to derive reliable measurements of the relevant parameters and their physical implications.
AB - Context. NGC 2264 is a young cluster whose accretion properties can be investigated in detail by taking advantage of the FLAMES data in the context of the Gaia-ESO Survey. In fact, the analysis of the Hα emission line profile can provide us with information about the accretion and ejection activity of young stars. However, a strong nebular emission that contributes to the Hα emission can alter the profiles, with consequences for their physical interpretation. Aims. Our study is aimed at investigating the accretion and ejection properties of NGC 2264 by applying a proper treatment of the sky contribution to the Hα and forbidden emission lines (FELs; [SII] and [NII] doublets). Methods. We developed a tool, the OHαNA-method, to handle the strong nebular contribution and spectra with spurious profiles of the Hα and FELs, namely altered Hα profiles or absorption features artificially created where emission lines (FELs) are expected. We derived the quantitative measurements of relevant parameters to describe the accretion and ejection processes in young members of NGC 2264, focusing on reliable quantities derived from the width of the lines, which is relatively unaffected by the nebular emission, unlike the intensity peak, which can be altered significantly. Results. We derive the quantitative measurements related to the Hα emission line and discuss the comparison between the original and sky-subtracted spectra. We thus reveal possible profile alterations with consequences for their physical interpretation. Furthermore, we show the analysis of the variability for multi-epoch observations, also deriving the velocity of the infalling and outflowing plasma from the wings of the broad Hα emission line (in accreting stars). We also explore the mass accretion rate versus full width at zero intensity of the Hα line, namely M versus FWZI(Hα), a correlation based on the width of the emission line, which is expected to be more robust with respect to any measurement derived from the peak (e.g., Hα10%) and possibly altered by the nebular contribution. Conclusions. We are able to ascertain that more than 20% of the confirmed accretors, which have already been identified in NGC 2264, are affected by the alteration of their line profiles due to the contribution of the nebular emission. Therefore, this is an important issue to consider when investigating accretion and ejection processes in young stellar clusters. While a small fraction of spectra can be unequivocally classified as either unaffected by nebular emission or dominated by nebular emission, the majority (> 90%) represent intermediate cases whose spectral features have to be investigated in detail to derive reliable measurements of the relevant parameters and their physical implications.
KW - Accretion, accretion disks
KW - Line: profiles
KW - Open clusters and associations: individual: NGC 2264
KW - Stars: formation
KW - Stars: pre-main sequence
KW - Stars: winds, outflows
UR - http://www.scopus.com/inward/record.url?scp=85093935515&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202037942
DO - 10.1051/0004-6361/202037942
M3 - Article
AN - SCOPUS:85093935515
SN - 0004-6361
VL - 642
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A56
ER -