J/A+A/642/A56 Diagnostic for accretion/outflow in NGC 2264 (Bonito+, 2020)
The Gaia-ESO Survey: A new diagnostic for accretion and outflow activity in
the young cluster NGC 2264.
Bonito R., Prisinzano L., Venuti L., Damiani F., Micela G., Sacco G.,
Traven G., Biazzo K., Sbordone L., Masseron T., Zwitter T., Gonneau A.,
Bayo A., Roccatagliata V., Randich S., Vink J.S., Jofre P., Flaccomio E.,
Magrini L., Carraro G., Morbidelli L., Frasca A., Monaco L., Rigliaco E.,
Worley C., Hourihane A., Gilmore G., Franciosini E., Lewis J., Koposov S.
<Astron. Astrophys. 642, A56 (2020)>
=2020A&A...642A..56B 2020A&A...642A..56B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Accretion
Keywords: stars: formation - stars: pre-main sequence -
accretion, accretion disks, outflow - stars: winds, outflows -
line: profiles - open clusters and associations: individual: NGC 2264
Abstract:
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.
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).
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.
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 dM/dt 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.
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.
Description:
Table 1. Cname, spectrum used for the measurements, object name,
signal-to-noise ratio, FWZI(Hα) (Å) and velocities of the
wings (blue and red part of the profile) of the Hα line in km/s
for all the objects here analyzed
The information presented in this table refer to all the GES targets,
independently with respect to previous membership selections and their
nature. The cases of interest for this paper are those with Hα
line in emission, but we also report the values for cases with
Hα line in absorption. Caution should be used when considering
the values presented in this table for parameters related to accretion
process when the Hα line is in absorption - see values of
Hα 10% width in the electronic version of this table. These
parameters have been derived from the non-skysubtracted spectra.
The complete version includes more parameters: the coordinates; the
values of Hα 10% width and the mass accretion rate (both the
value from the Natta et al. (2004A&A...424..603N 2004A&A...424..603N) relation and the new
value from the Eq. 1), that have been derived from the
non-skysubtracted spectra (these parameters can be altered by the
nebular emission as discussed in the main text); the extremes of the
[SII] and [NII] doublets calculated by the tool and derived from the
sky-subtracted spectra that give an indication of possible spurious
absorption lines due to an over-subtraction of the nebular
contribution.
All the parameters have been derived in this work.
Table A.1. Cname, spectrum used for the measurements, extremes of the
[SII] doublet calculated by the tool, and FWZI for the spectra
classified as 'good' using our tool.
Among these cases, ∼90% with Hα line in emission are defined
here as "confident accretors". Caution should be used when considering
the values presented in this table for parameters related to accretion
process when the Hα line is in absorption - see values of
Hα 10% width in the electronic version of Table 1. The complete
version of this Table is available in the electronic version of the
paper, and includes the extremes of the [NII] doublet and the object
name. The FELs extremes have been derived by the sky-subtracted
spectra, while the FWZI(Hα) values by the non-skysubtracted
spectra.
Table A.2. Cname, spectrum used for the measurements, extremes of the
[SII] doublet calculated by the tool, and FWZI for the spectra
classified as 'bad using our tool.
The table includes the extremes of the [NII] doublet and the object
name. The FELs extremes have been derived by the sky-subtracted
spectra, while the FWZI(Hα) values by the non-skysubtracted
spectra.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 183 5440 Parameters for all the objects analysed
(1843 objects)
tablea1.dat 120 218 Parameters for the spectra classified as 'good'
using our tool (62 objects)
tablea2.dat 111 56 Parameters for the spectra classified as 'bad'
using our tool (55 objects)
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Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Cname Designation
18- 39 A22 --- Nspec Name of the spectrum
41- 50 A10 --- Object Name of the object
52- 54 I3 --- S/N Signal-to-noise ratio
57- 61 F5.2 0.1nm FWZI(Ha) Full width at zero intensity of
the Halpha line
63- 66 I4 km/s vel(blue) Velocity derived from the blue wing of
the Halpha line
69- 71 I3 km/s vel(red) Velocity derived from the red wing of
the Halpha line
74- 82 F9.5 deg RAdeg Right Ascension (J2000)
84- 91 F8.5 deg DEdeg Declination (J2000)
93- 98 F6.2 0.1nm Ha10(A) Width of the Halpha line at 10% of
its peak (in Angstroem)
100-104 I5 km/s Ha10(km/s) Width of the Halpha line at 10% of
its peak (in km/s)
107-112 F6.2 [Msun/yr] log(dM/dt) log of the mass accretion rate
114-119 F6.2 [Msun/yr] log(dM/dt)new log of the mass accretion rate
as derived from Eq. 1
121-127 F7.2 0.1nm [SII]6717min ?=-99.90 Minimum of [SII]6717 line
from our tool (1)
129-135 F7.2 0.1nm [SII]6717max ?=-99.90 Maximum of [SII]6717 line
from our tool (1)
137-143 F7.2 0.1nm [SII]6731min ?=-99.90 Minimum of [SII]6731 line
from our tool (1)
145-151 F7.2 0.1nm [SII]6731max ?=-99.90 Maximum of [SII]6731 line
from our tool (1)
153-159 F7.2 0.1nm [NII]6548min ?=-99.90 Minimum of [NII]6548 line
from our tool (1)
161-167 F7.2 0.1nm [NII]6548max ?=-99.90 Maximum of [NII]6548 line
from our tool (1)
169-175 F7.2 0.1nm [NII]6583min ?=-99.90 Minimum of [NII]6583 line
from our tool (1)
177-183 F7.2 0.1nm [NII]6583max ?=-99.90 Maximum of [NII]6583 line
from our tool (1)
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Note (1): -99.90 if in absorption.
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Cname Designation
18- 39 A22 --- Nspec Name of the spectrum for 'good' cases
41- 47 F7.2 0.1nm [SII]6717min Minimum of [SII]6717 line from our tool
(Angstroem)
49- 55 F7.2 0.1nm [SII]6717max Maximum of [SII]6717 line from our tool
(Angstroem)
57- 63 F7.2 0.1nm [SII]6731min Minimum of [SII]6731 line from our tool
(Angstroem)
65- 71 F7.2 0.1nm [SII]6731max Maximum of [SII]6731 line from our tool
(Angstroem)
73- 77 F5.2 0.1nm FWZI(Ha) Full width at zero intensity of the Halpha
line (Angstroem)
79- 85 F7.2 0.1nm [NII]6548min Minimum of [NII]6548 line from our tool
(Angstroem)
87- 93 F7.2 0.1nm [NII]6548max Maximum of [NII]6548 line from our tool
(Angstroem)
95-101 F7.2 0.1nm [NII]6583min Minimum of [NII]6583 line from our tool
(Angstroem)
103-109 F7.2 0.1nm [NII]6583max Maximum of [NII]6583 line from our tool
(Angstroem)
111-120 A10 --- Object Name of the object
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Cname Designation
18- 39 A22 --- Nspec Name of the spectrum for 'bad' cases
41- 46 F6.2 0.1nm [SII]6717min ?=-99.90 Minimum of [SII]6717 line from
our tool (Angstroem) (1)
48- 53 F6.2 0.1nm [SII]6717max ?=-99.90 Maximum of [SII]6717 line from
our tool (Angstroem) (1)
55- 60 F6.2 0.1nm [SII]6731min ?=-99.90 Minimum of [SII]6731 line from
our tool (Angstroem) (1)
62- 67 F6.2 0.1nm [SII]6731max ?=-99.90 Maximum of [SII]6731 line from
our tool (Angstroem) (1)
69- 72 F4.2 0.1nm FWZI(Ha) Full width at zero intensity of the Halpha
line (Angstroem) (1)
74- 79 F6.2 0.1nm [NII]6548min ?=-99.90 Minimum of [NII]6548 line from
our tool (Angstroem) (1)
81- 86 F6.2 0.1nm [NII]6548max ?=-99.90 Maximum of [NII]6548 line from
our tool (Angstroem) (1)
88- 93 F6.2 0.1nm [NII]6583min ?=-99.90 Minimum of [NII]6583 line from
our tool (Angstroem) (1)
95-100 F6.2 0.1nm [NII]6583max ?=-99.90 Maximum of [NII]6583 line from
our tool (Angstroem) (1)
102-111 A10 --- Object Name of the object
--------------------------------------------------------------------------------
Note (1): -99.90 = if in absorption
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Acknowledgements:
Rosaria Bonito, rosaria.bonito(at)inaf.it
(End) Rosaria Bonito [NAF - Obs. of Palermo], Patricia Vannier [CDS] 13-Aug-2020