J/MNRAS/506/4232 Chemical abundances of the Orion Complex (Kos+, 2021)
The GALAH survey, Chemical homogeneity of the Orion complex
Kos J., Bland-Hawthorn J., Buder S., Nordlander T., Spina L., Beeson K.L.,
Lind K., Asplund M., Freeman K., Hayden M.R., Lewis G.F., Martell S.L.,
Sharma S., De Silva G., Simpson J.D., Zucker D.B., Zwitter T., Cotar K.,
Horner J., Ting Y.-S., Traven G.
<Mon. Not. R. Astron. Soc. 506, 4232-4250 (2021)>
=2021MNRAS.506.4232K 2021MNRAS.506.4232K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; YSOs ; Optical ; Infrared sources ;
Spectroscopy ; Effective temperatures ; Rotational velocities ;
Abundances
Keywords: astrochemistry - stars: abundances - stars: formation -
stars: pre-main-sequence - open clusters and associations: general
Abstract:
Due to its proximity, the Orion star forming region is often used as a
proxy to study processes related to star formation and to observe
young stars in the environment they were born in. With the release of
Gaia DR2, the distance measurements to the Orion complex are now good
enough that the 3D structure of the complex can be explored. Here we
test the hypothesis that, due to non- trivial structure and dynamics,
and age spread in the Orion complex, the chemical enrichment of
youngest stars by early core-collapse supernovae can be observed. We
obtained spectra of 794 stars of the Orion complex with the HERMES
spectrograph at the Anglo Australian telescope as a part of the GALAH
and GALAH-related surveys. We use the spectra of ∼300 stars to derive
precise atmospheric parameters and chemical abundances of 25 elements
for 15 stellar clusters in the Orion complex. We demonstrate that the
Orion complex is chemically homogeneous and that there was no
self-pollution of young clusters by core-collapse supernovae from
older clusters; with a precision of 0.02 dex in relative alpha-elements
abundance and 0.06 dex in oxygen abundance we would have been able to
detect pollution from a single supernova, given a fortunate location
of the SN and favourable conditions for ISM mixing. We estimate that
the supernova rate in the Orion complex was very low, possibly
producing no supernova by the time the youngest stars of the observed
population formed (from around 21 to 8 Myr ago).
Description:
This work relies on the observing and data reduction infrastructure of
the GALAH survey. Some data were taken as part of the regular GALAH
survey, but most were obtained on a separate observing proposal in
order to target fainter stars and specific populations. Fields from
the regular GALAH survey were observed between 2014 and 2018 and the
fainter fields of the dedicated survey were observed in 2019 February.
Instead of using a straightforward selection function, like that for
GALAH, we first found Orion complex members using the Gaia DR2
position-proper motion-parallax space and the clustering algorithm
presented in Section 3. Then priority was given to stars with Gaia G
magnitudes between 12.0 and 14.5 (roughly 12.25 < VJK < 14.75). The
remaining fibres were filled with Orion members up to one magnitude
fainter. Orion complex members filled most of the fibre positioner's
400 fibres (fibres of HERMES instrument at the 3.9 m
Anglo-Australian Telescope at the Siding Spring Observatory) and any
remaining fibres were positioned to capture field stars in the same
magnitude range. Spectra from all observing programs cover the same
wavelength range: 4718-4903 Å (blue channel), 5649-5873 Å
(green channel), 6481-6739 Å (red channel), and 7590-7890 Å
(infrared channel). All fields/spectra were reduced with the same
GALAH pipeline, regardless from which survey program they were taken.
All together we observed 794 members. Most of the observed stars were
not analysed fully. Final analysis of chemical homogeneity omits many
stars as they are too faint for anything more than a radial velocity
measurement (48 per cent of all observed stars). Nevertheless, these
stars still help constrain the isochrone fits used for age
measurements. Stars are also excluded from the final analysis if they
are hotter than Teff > 7750 K (6 per cent), rotate faster than 40 km/s
(4 per cent), or are double lined binary stars (1 per cent). Some spectra
were rejected based on poor fits of spectral templates (6 per cent).
Finally, 35 per cents of the 794 Orion complex members (277 stars)
constitute our final sample. As fully detailed in the section 4,
element abundances are derived following a bayesian fiiting method
which based on priors parameters such as Teff, log g, v*sin(i),
[M/H] and [α/Fe] where gaussian probability density functions
are first determined. Then, thanks of this bayesian method we fit
synthetic spectra with real spectra to obtain element abundances. All
results are reported in the table.dat.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 350 277 *Photometric, spectroscopic parameters and
abundances for each stars
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Note on table.dat: As explained in the section 4 Spectroscopic parameters and
abundances, we use a Bayesian fitting schema to derive these values,
(general details in the section 4.1.1 General description).
Moreover, all abundances are given as ratio to sun abundances as
[X/H] = log(NX/NH)star - log(NX/NH)☉.
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/MNRAS/478/4513 : GALAH Survey DR2 (Buder+, 2018)
J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Cluster Name of the cluster star's host (Cluster)
15- 33 I19 --- GaiaDR2 Unique source identifier (id)
35- 41 F7.4 deg RAdeg Barycentric right ascension (ICRS)
at Ep=2015.5 (ra)
43- 49 F7.4 deg DEdeg Barycentric declination (ICRS)
at Ep=2015.5 (dec)
51- 56 F6.1 K Teff Effective temperature (T_eff)
58- 61 F4.1 K e_Teff Mean error on Teff (Teffe)
63- 66 F4.2 [cm/s2] logg Surface gravity (log_g)
68- 72 F5.2 [Sun] [M/H] Metallicity ([M/H])
74- 77 F4.2 [Sun] e_[M/H] Mean error on [M/H] ([M/H]_e)
79- 83 F5.2 [Sun] [alpha/Fe] Alpha-element abundance with lines in the
covered bands are Mg, Si, Ca, Ti, and O
([alpha/Fe])
85- 88 F4.2 [Sun] e_[alpha/Fe] Mean error on [alpha/Fe] ([alpha/Fe]_e)
90- 94 F5.2 km/s vsini Projected rotational speed (vsini)
96- 99 F4.2 km/s e_vsini Mean error on vsini (vsini_e)
101-104 F4.2 [Sun] [Li/H] ?=- Lithium abundance (A_Li)
106-109 F4.2 [Sun] e_[Li/H] ?=- Mean error on [Li/H] (ALie)
111-115 F5.2 [Sun] [O/H] ?=- Oxygen abundance (A_O)
117-120 F4.2 [Sun] e_[O/H] ?=- Mean error on [O/H] (AOe)
122-125 F4.2 [Sun] [Na/H] ?=- Sodium abundance (A_Na)
127-130 F4.2 [Sun] e_[Na/H] ?=- Mean error on [Na/H] (ANae)
132-135 F4.2 [Sun] [Mg/H] ?=- Magnesium abundance (A_Mg)
137-140 F4.2 [Sun] e_[Mg/H] ?=- Mean error on [Mg/H] (AMge)
142-145 F4.2 [Sun] [A/H] ?=- Aluminium abundance (A_Al)
147-150 F4.2 [Sun] e_[A/H] ?=- Mean error on [A/H] (AAle)
152-155 F4.2 [Sun] [Si/H] ?=- Silicium abundance (A_Si)
157-160 F4.2 [Sun] e_[Si/H] ?=- Mean error on [Si/H] (ASie)
162-165 F4.2 [Sun] [K/H] ?=- Potassium abundance (A_K)
167-170 F4.2 [Sun] e_[K/H] ?=- Mean error on [K/H] (AKe)
172-175 F4.2 [Sun] [Ca/H] ?=- Calcium abundance (A_Ca)
177-180 F4.2 [Sun] e_[Ca/H] ?=- Mean error on [Ca/H] (ACae)
182-185 F4.2 [Sun] [Sc/H] ?=- Scandium abundance (A_Sc)
187-190 F4.2 [Sun] e_[Sc/H] ?=- Mean error on (ASce)
192-195 F4.2 [Sun] [Ti/H] ?=- Titanium abundance (A_Ti)
197-200 F4.2 [Sun] e_[Ti/H] ?=- Mean error on [Ti/H] (ATie)
202-205 F4.2 [Sun] [V/H] ?=- Vanadium abundance (A_V)
207-210 F4.2 [Sun] e_[V/H] ?=- Mean error on [V/H] (AVe)
212-215 F4.2 [Sun] [Cr/H] ?=- Chromium abundance (A_Cr)
217-220 F4.2 [Sun] e_[Cr/H] ?=- Mean error on [Cr/H] (ACre)
222-225 F4.2 [Sun] [Mn/H] ?=- Manganese abundance (A_Mn)
227-230 F4.2 [Sun] e_[Mn/H] ?=- Mean error on (AMne)
232-235 F4.2 [Sun] [Fe/H] ?=- Iron abundance (A_Fe)
237-240 F4.2 [Sun] e_[Fe/H] ?=- Mean error on [Fe/H] (AFee)
242-245 F4.2 [Sun] [Co/H] ?=- Cobalt abundance (A_Co)
247-250 F4.2 [Sun] e_[Co/H] ?=- Mean error on [Co/H] (ACoe)
252-255 F4.2 [Sun] [Ni/H] ?=- Nickel abundance (A_Ni)
257-260 F4.2 [Sun] e_[Ni/H] ?=- Mean error on [Ni/H] (ANie)
262-265 F4.2 [Sun] [Cu/H] ?=- Copper abundance (A_Cu)
267-270 F4.2 [Sun] e_[Cu/H] ?=- Mean error on [Cu/H] (ACue)
272-275 F4.2 [Sun] [Zn/H] ?=- Zinc abundance (A_Zn)
277-280 F4.2 [Sun] e_[Zn/H] ?=- Mean error on [Zn/H] (AZne)
282-285 F4.2 [Sun] [Rb/H] ?=- Rubidium abundance (A_Rb)
287-290 F4.2 [Sun] e_[Rb/H] ?=- Mean error on [Rb/H] (ARbe)
292-295 F4.2 [Sun] [Y/H] ?=- Yttrium abundance (A_Y)
297-300 F4.2 [Sun] e_[Y/H] ?=- Mean error on [Y/H] (AYe)
302-305 F4.2 [Sun] [Zr/H] ?=- Zirconium abundance (A_Zr)
307-310 F4.2 [Sun] e_[Zr/H] ?=- Mean error on [Zr/H] (AZre)
312-315 F4.2 [Sun] [Ba/H] ?=- Barium abundance (A_Ba)
317-320 F4.2 [Sun] e_[Ba/H] ?=- Mean error on [Ba/H] (ABae)
322-325 F4.2 [Sun] [Ce/H] ?=- Cerium abundance (A_Ce)
327-330 F4.2 [Sun] e_[Ce/H] ?=- Mean error on [Ce/H] (ACee)
332-335 F4.2 [Sun] [Nd/H] ?=- Neodymium abundance (A_Nd)
337-340 F4.2 [Sun] e_[Nd/H] ?=- Mean error on [Nd/H] (ANde)
342-345 F4.2 [Sun] [Eu/H] ?=- Europium abundance (A_Eu)
347-350 F4.2 [Sun] e_[Eu/H] ?=- Mean error on [Eu/H] (AEue)
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 25-Jun-2024