J/ApJ/975/162 Spectra of brown dwarf candidates in ONC from JWST (Luhman+, 2024)
JWST/NIRSpec observations of brown dwarfs in the Orion Nebula Cluster.
Luhman K.L., Alves de Oliveira C., Baraffe I., Chabrier G., Manjavacas E.,
Parker R.J., Tremblin P.
<Astrophys. J., 975, 162 (2024)>
=2024ApJ...975..162L 2024ApJ...975..162L
ADC_Keywords: Stars, brown dwarf; YSOs; Star Forming Region; Clusters, open;
MK spectral classification; Spectra, infrared
Keywords: Brown dwarfs ; L dwarfs ; Star forming regions ;
Initial mass function ; James Webb Space Telescope ;
Circumstellar disks ; Protoplanetary disks ; Proplyds ; Protostars
Abstract:
We have used the multiobject mode of the Near-Infrared Spectrograph
(NIRSpec) on board the James Webb Space Telescope (JWST) to obtain
low-resolution 1-5um spectra of 22 brown dwarf candidates in the
Orion Nebula Cluster, which were selected with archival images from
the Hubble Space Telescope. One of the targets was previously
classified as a Herbig-Haro (HH) object and exhibits strong emission
in HI, H2, and the fundamental band of CO, further demonstrating
that HH objects can have bright emission in that CO band. The
remaining targets have late spectral types (M6.5 to early L) and are
young based on gravity-sensitive features, as expected for low-mass
members of the cluster. According to theoretical evolutionary models,
these objects should have masses that range from the hydrogen burning
limit to 0.003-0.007M☉. Two of the NIRSpec targets were
identified as proplyds in earlier analysis of Hubble images. They have
spectral types of M6.5 and M7.5, making them two of the coolest and
least massive known proplyds. Another brown dwarf shows absorption
bands at 3-5um from ices containing H2O, CO2, OCN-, and CO,
indicating that it is either an edge-on class II system or a class I
protostar. It is the coolest and least massive object that has
detections of these ice features. In addition, it appears to be the
first candidate for a protostellar brown dwarf that has spectroscopy
confirming its late spectral type.
Description:
We pursued spectroscopy of brown dwarf candidates in the ONC with
NIRSpec on the James Webb Space Telescope (JWST) through the
guaranteed time observation program 1228 (PI: C. Alves de Oliveira)
with 2.6h allocated. The targets for NIRSpec were selected from
near-IR images obtained with the Wide Field Camera 3 (WFC3) on the
Hubble Space Telescope (HST) in 2015 through Treasury program 13826
(PI: M. Robberto). The observations utilized NIRSpec's microshutter
assembly (MSA).
We used the MSA Planning Tool (MPT) in the Astronomer's Proposal Tool
(APT) to design two MSA configurations for observing a subset of the
brown dwarf candidates identified with WFC3. A total of 14 targets were
observed in each of the two MSA configurations. Three sources were
present in both configurations, so the total number of targets was 25.
The observations with the two MSA configurations were performed on
2023 February 22 (UT). At each of the three nod positions, one
exposure was taken, which utilized five groups, six integrations, and
the NRSRAPID readout pattern. The latter was chosen to avoid
saturation for the brightest targets. In a given MSA configuration,
the total exposure time for three exposures was 1160s. The charged
time was 2.58hr.
Objects:
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RA (2000) DE Designation(s)
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05 34 59.99 -05 29 00.0 ONC = NAME Orion Nebula Cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 53 22 Sources in the Orion Nebula Cluster (ONC) observed
with JWST/NIRSpec
sp/* . 22 Individual JWST/NIRSpec spectra of brown dwarf
candidates in ASCII format
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See also:
J/AJ/111/846 : Orion HST survey (O'Dell+ 1996)
J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997)
J/A+A/337/403 : Low-mass stars evolutionary models (Baraffe+ 1998)
J/AJ/117/1375 : Orion Trapezium cluster (Simon+, 1999)
J/ApJ/540/236 : KH phot. of Orion Nebula Cluster (Hillenbrand+, 2000)
J/ApJ/540/1016 : K-band & NICMOS phot.: Trapezium Cluster (Luhman+, 2000)
J/ApJ/573/366 : Infrared photometry of Trapezium cluster (Muench+, 2002)
J/other/ARA+A/43.195 : L and T dwarf stars (Kirkpatrick, 2005)
J/MNRAS/361/211 : JHK photometry of brown dwarfs in Orion (Lucas+, 2005)
J/ApJS/179/249 : Low-luminosity embedded protostar population (Dunham+, 2008)
J/AJ/136/2136 : HST/ACS Atlas of Great Orion Nebula proplyds (Ricci+, 2008)
J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)
J/AJ/139/950 : JHKs photometry in ONC (Robberto+, 2010)
J/A+A/534/A10 : HST/NICMOS III imaging in ONC (Andersen+, 2011)
J/ApJ/748/14 : ONC population data from WFI observations (Da Rio+, 2012)
J/AJ/146/85 : Spec. types: 1576 optical stars in ONC (Hillenbrand+, 2013)
J/ApJS/207/10 : HST Treasury Program on the ONC (Robberto+, 2013)
J/ApJ/782/8 : Spectroscopy of 104 objects in the ONC (Ingraham+, 2014)
J/MNRAS/461/1734 : HAWK-I JHK phot. of the Orion Nebula Cloud (Drass+, 2016)
J/ApJ/826/16 : ALMA & GeMS observations of the OMC1 region (Eisner+, 2016)
J/A+A/587/A153 : VISION I. VISTA Orion A Survey (Meingast+, 2016)
J/AJ/153/46 : Spectroscopy of candidate members in Taurus (Luhman+, 2017)
J/ApJ/896/79 : HST survey: ONC in H20 1.4um abs. band. I. (Robberto+, 2020)
J/AJ/163/26 : Sco-Cen memb. & sp. obs. in other clouds (Luhman+, 2022)
J/A+A/657/A131 : Ten new systems with O stars (Maiz Apellaniz+, 2022)
J/AJ/168/230 : Phot. substellar candidates in ONC with JWST (Luhman, 2024)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [67/143] Identifier
5- 18 A14 --- OName Other name(s)
20- 28 F9.6 deg RAdeg [83.78/83.85] Right ascension (J2000)
30- 38 F9.6 deg DEdeg [-5.4/-5.3] Declination (J2000)
40- 44 A5 --- SpT Spectral type
46- 49 F4.2 --- AK [0.03/1.6]? Extinction estimate
51- 53 A3 --- IRex? Infrared excess? (1)
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Note (1): Flags as follows:
yes = >0.5mag at 3-5um (3 occurrences)
no = no IR excess (9 occurrences)
no? = extinctions and photospheric colors are uncertain, difficult to
reliably identify excesses from disks; no large excess but smaller
excesses are possible (5 occurrences)
? = may have small excesses (∼0.2mag), but data at longer wavelengths
are needed for confirming the presence of disks (4 occurrences)
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.3 um lambda [0.6/5.3] Wavelength
7- 13 F7.4 --- Flux [-0.11/10.6] Fλ, normalized by the
flux density at 1.68um
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 30-Jun-2025