J/AJ/153/240 ALMA survey of protoplanetary disks in sigma Ori (Ansdell+, 2017)
An ALMA survey of protoplanetary disks in the σ Orionis cluster.
Ansdell M., Williams J.P., Manara C.F., Miotello A., Facchini S.,
van der Marel N., Testi L., van Dishoeck E.F.
<Astron. J., 153, 240-240 (2017)>
=2017AJ....153..240A 2017AJ....153..240A (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Associations, stellar ; YSOs ; Radio lines ;
Photometry, millimetric/submm ; Spectral types ; Stars, masses
Keywords: accretion, accretion disks - circumstellar matter -
planets and satellites: formation - protoplanetary disks -
stars: pre-main sequence - stars: protostars
Abstract:
The σ Orionis cluster is important for studying protoplanetary
disk evolution, as its intermediate age (∼3-5Myr) is comparable to the
median disk lifetime. We use ALMA to conduct a high-sensitivity survey
of dust and gas in 92 protoplanetary disks around σ Orionis
members with M*≳0.1M☉. Our observations cover the 1.33mm
continuum and several CO J=2-1 lines: out of 92 sources, we detect 37
in the millimeter continuum and 6 in 12CO, 3 in 13CO, and none in
C18O. Using the continuum emission to estimate dust mass, we find
only 11 disks with Mdust≳10M⊕, indicating that after only a
few Myr of evolution most disks lack sufficient dust to form giant
planet cores. Stacking the individually undetected continuum sources
limits their average dust mass to 5x lower than that of the faintest
detected disk, supporting theoretical models that indicate rapid
dissipation once disk clearing begins. Comparing the protoplanetary
disk population in σ Orionis to those of other star-forming
regions supports the steady decline in average dust mass and the
steepening of the Mdust-M* relation with age; studying these
evolutionary trends can inform the relative importance of different
disk processes during key eras of planet formation. External
photoevaporation from the central O9 star is influencing disk
evolution throughout the region: dust masses clearly decline with
decreasing separation from the photoionizing source, and the handful
of CO detections exist at projected separations of >1.5pc.
Collectively, our findings indicate that giant planet formation is
inherently rare and/or well underway by a few Myr of age.
Description:
Our sample consists of the 92 Young Stellar Objects (YSOs) in σ
Orionis with infrared excesses consistent with the presence of a
protoplanetary disk. hese sources are identified by cross-matching the
Class II and transition disk (TD) candidates from the Spitzer survey
of Hernandez et al. 2007 (Cat. J/ApJ/662/1067) with the Mayrit catalog
(Caballero 2008, Cat. J/A+A/478/667). Both catalogs are expected to be
complete down to the brown dwarf limit. Disk classifications are based
on the Spitzer/Infrared Array Camera (IRAC) Spectral Energy
Distribution (SED) slope, as described in Hernandez et al. 2007 (Cat.
J/ApJ/662/1067). We also include in our sample a Class I disk (source
1153), as it is located near the Spitzer/IRAC color cutoff for Class
II disks.
Our Band 6 Atacama Large Millimeter/sub-millimeter Array (ALMA)
observations were obtained on 2016 July 30 and 31 during Cycle 3
(Project ID: 2015.1.00089.S; PI: Williams). The array configuration
used 36 and 37 12m antennas on July 30 and 31, respectively, with
baselines of 15-1124m on both runs. The correlator setup included two
broadband continuum windows centered on 234.293 and 216.484GHz with
bandwidths of 2.000 and 1.875GHz and channel widths of 15.625 and
0.976MHz, respectively. The bandwidth-weighted mean continuum
frequency was 225.676GHz (1.33mm). The spectral windows covered the
12CO (230.538GHz), 13CO (220.399GHz), and C18O (219.560GHz)
J=2-1 transitions at velocity resolutions of 0.16-0.17km/s. These
spectral windows were centered on 230.531, 220.392, and 219.554GHz
with bandwidths of 11.719MHz and channel widths of 0.122MHz.
On-source integration times were 1.2 minutes per object for an average
continuum rms of 0.15mJy/beam (Table1). This sensitivity was based on
the James Clerk Maxwell Telescope (JCMT)/Submillimeter Common User
Bolometer Array (SCUBA)-2 survey of σ Orionis disks by Williams
et al. 2013 (Cat. J/MNRAS/435/1671), who found that stacking their
individual non-detections revealed a mean 850µm continuum signal of
1.3mJy at 4σ significance. The sensitivity of our ALMA survey
was therefore chosen to provide ∼3-4σ detections of such disks
at 1.3mm, based on an extrapolation of the 850µm mean signal using
a spectral slope of α=2-3.
Table1 presents the 1.33mm continuum flux densities and associated
uncertainties (F1.33mm). Table2 gives our integrated line fluxes or
upper limits.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 80 92 Continuum properties
table2.dat 38 92 Gas properties
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See also:
J/A+A/594/A85 : 2D disk models from CO isotopologues line (Miotello+, 2016)
J/AJ/152/213 : Interferometry and spectroscopy of sig Ori (Schaefer+, 2016)
J/ApJ/831/125 : ALMA 887um obs. of ChaI SFR (Pascucci+, 2016)
J/ApJ/828/46 : ALMA survey of Lupus protoplanetary disks. (Ansdell+, 2016)
J/ApJ/827/142 : ALMA observations of GKM stars in U. Sco (Barenfeld+, 2016)
J/ApJ/794/36 : sig Orionis cluster stellar population (Hernandez+, 2014)
J/MNRAS/435/1671 : SCUBA-2 850um survey in sig Ori cluster (Williams+, 2013)
J/A+A/548/A56 : X-shooter spectra of 12 YSOs (Rigliaco+, 2012)
J/A+A/478/667 : The Mayrit catalogue (Caballero, 2008)
J/ApJ/662/1067 : Sptizer observations of sigma Orionis (Hernandez+, 2007)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- [HHM2007] [73/1369] Source identification number (G1)
6- 7 I2 h RAh Hour of Right Ascension (J2000) (1)
9- 10 I2 min RAm Minute of Right Ascension (J2000) (1)
12- 17 F6.3 s RAs Second of Right Ascension (J2000) (1)
19 A1 --- DE- Sign of the Declination (J2000) (1)
20- 21 I2 deg DEd Degree of Declination (J2000) (1)
23- 24 I2 arcmin DEm Arcminute of Declination (J2000) (1)
26- 30 F5.2 arcsec DEs Arcsecond of Declination (J2000) (1)
32- 35 A4 --- SpT Spectral type (2)
37- 39 F3.1 --- e_SpT Uncertainty in SpT
41- 43 A3 --- r_SpT Reference for SpT (H14, R12, or VJ) (3)
45- 48 F4.2 Msun Mass [0.04/1.71] Stellar mass (M*) (4)
50- 53 F4.2 Msun e_Mass [0.01/0.32] Uncertainty in Mass (4)
55- 59 F5.2 mJy F1.33 [-0.27/15.38] Atacama Large Millimeter/sub-
millimeter Array (ALMA) 1.33mm (225.676GHz)
continuum emission flux density (F1.33mm)
61- 64 F4.2 mJy e_F1.33 [0.13/0.25] Uncertainty in F1.33 (5)
66- 69 F4.2 mJy/beam rms [0.13/0.18] Root-mean-square
71- 75 F5.2 Mgeo Mdust [-1.2/68.48] Dust mass (Mdust) (6)
77- 80 F4.2 Mgeo e_Mdust [0.57/1.12] Uncertainty in Mdust
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Note (1): We detect only 37 out of the 92 observed sources at >3σ
significance (Figure2 in the paper). For detections, the source locations
are the fitted source centers output by uvmodelfit, while for
non-detections they are simply the phase centers of the Atacama Large
Millimeter/sub-millimeter Array (ALMA) observations, which were chosen
based on 2MASS positions. The average offsets from the phase centers for
the detections are Δα=0.057'' and Δδ=-0.096'' (1.9
and -3.2 pixels), both much smaller than the average beam size (Section 3
in the paper).
Note (2): Spectral types were primarily taken from the homogenous sample of
low-resolution optical spectra analyzed in Hernandez et al. 2014
(Cat. J/ApJ/794/36), but supplemented with those from medium-resolution
VLT/X-Shooter spectra when available from Rigliaco et al. 2012
(Cat. J/A+A/548/A56). For the 23 sources that lack spectroscopic
information, we estimate their spectral types using an empirical relation
between V-J color and stellar spectral type; the relation was derived by
measuring synthetic photometry from flux-calibrated VLT/X-Shooter spectra
of Young Stellar Objects (YSOs) with spectral types from G5 to M9.5, then
performing a non-parametric fit of the V-J color versus spectral type
relation (Manara et al. 2017, in prep.). For these sources with
photometrically derived spectral types, we cautiously assume uncertainties
of ±2 spectral subtypes. We note that only 5 out of the 37 continuum
detections have photometrically derived spectral types, which are less
precise than the spectroscopically determined spectral types (Section 2).
Note (3): Reference codes are defined as follows:
H14 = Hernandez et al. 2014 (Cat. J/ApJ/794/36);
R12 = Rigliaco et al. 2012 (Cat. J/A+A/548/A56);
VJ = derived from V-J color indices (see Section 2).
Note (4): We estimate M* values for our sample by comparing their positions on
the Hertzsprung-Russel (HR) diagram to the evolutionary models of Siess et
al. 2000A&A...358..593S 2000A&A...358..593S. In order to place our targets on the HR diagram,
we convert their spectral types to stellar effective temperatures (Teff)
and derive their stellar luminosities (L*) from J-band magnitudes using
the relations in Herczeg & Hillenbrand 2015ApJ...808...23H 2015ApJ...808...23H. The
uncertainties on L* are obtained by propagating the uncertainties on
spectral type and bolometric correction, and thus on distance and optical
extinction (AV). We then calculate the uncertainties on M* using a
Monte Carlo (MC) method, where we take the standard deviation of 1000
estimates of M*, each calculated after randomly perturbing the derived
values of Teff and L* by their uncertainties.
Note (5): The uncertainties are statistical errors and do not include the 10%
absolute flux calibration error (Section 3 in the paper).
Note (6):
Our Mdust estimates, derived using Equation (1) with our F1.33mm
measurements (Section 4.1):
Mdust=Fνd2/KνBν(Tdust), where:
Bν(Tdust) = The Planck function for a characteristic dust
temperature of Tdust=20K (the median for Taurus disks;
Andrews & Williams 2005ApJ...631.1134A 2005ApJ...631.1134A);
Kν = The dust grain opacity. We take Kν as 10cm2/g at
1000GHz and use an opacity power-law index of β=1
(Beckwith et al. 1990AJ.....99..924B 1990AJ.....99..924B);
d = The source distance, taken as 385pc based on the
updated parallax of the σ Ori triple system
(Schaefer et al. 2016, Cat. J/AJ/152/213).
Equation (1) can therefore be approximated as:
Mdust≃1.34*10-5F1.33mm,
where F1.33mm is in mJy and Mdust is in M☉.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- [HHM2007] [73/1369] Source identification number (G1)
6 A1 --- l_F12CO [<] Upper limit flag on FC12O
7- 10 I4 mJy.km/s F12CO [63/1204] The 12CO (230.538GHz) line
intensity (F12CO) (7)
12- 13 I2 mJy.km/s e_F12CO [33/88]? Uncertainty in F12CO (7)
15 A1 --- l_F13CO [<] Upper limit flag on F13CO
16- 18 I3 mJy.km/s F13CO [72/326] The 13CO (220.399 GHz) line
intensity (F13CO) (7)
20- 21 I2 mJy.km/s e_F13CO [54/68]? Uncertainty in F13CO (7)
23 A1 --- l_FC18O [<] Upper limit flag on FC18O
24- 25 I2 mJy.km/s FC18O [48/81] The C18O (219.560GHz) line
intensity (FC18O) (7)
27- 29 F3.1 MJup Mgas [2.4/7.1]? Gas mass (Mgas)
31- 33 F3.1 MJup b_Mgas [1/1]? Lower boundary (minimum mass) of Mgas
(Mgas,min)
35- 38 F4.1 MJup B_Mgas [1/31.4] Upper boundary (maximum mass) of
Mgas (Mgas,max)
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Note (7): Of the 92 targets, only 6 are detected in 12CO, 3 are detected in
13CO, and none are detected in C18O with >4σ significance. All
sources detected in 12CO are detected in the continuum, and all sources
detected in 13CO are detected in 12CO.
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Global Notes:
Note (G1): From Hernandez, Hartmann, Megeath et al. 2007 (Cat. J/ApJ/662/1067).
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 16-Aug-2017