J/A+A/600/A141 Orion A integral shaped filament image (Kainulainen+, 2017)
Resolving the fragmentation of high line-mass filaments with ALMA:
the integral shaped filament in Orion A.
Kainulainen J., Stutz A.M., Stanke T., Abreu-Vicente J., Beuther H.,
Henning T., Johnston K.G., Megeath S.T.
<Astron. Astrophys. 600, A141 (2017)>
=2017A&A...600A.141K 2017A&A...600A.141K (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Radio continuum ; Millimetric/submm sources
Keywords: ISM: clouds - ISM: structure - stars: formation -
ISM: individual objects: OMC-2 - radio continuum: ISM
Abstract:
We study the fragmentation of the nearest high line-mass filament, the
integral shaped filament (ISF, line-mass ∼400M☉/pc) in the Orion
A molecular cloud. We have observed a 1.6pc long section of the ISF
with the Atacama Large Millimetre/submillimeter Array (ALMA) at 3mm
continuum emission, at a resolution of ∼3" (1200AU). We identify from
the region 43 dense cores with masses about a solar mass. 60% of the
ALMA cores are protostellar and 40% are starless. The nearest
neighbour separations of the cores do not show a preferred
fragmentation scale; the frequency of short separations increases down
to 1200AU. We apply a two-point correlation analysis on the dense core
separations and show that the ALMA cores are significantly grouped at
separations below ∼17000AU and strongly grouped below ∼6000AU. The
protostellar and starless cores are grouped differently: only the
starless cores group strongly below ∼6000AU. In addition, the spatial
distribution of the cores indicates periodic grouping of the cores
into groups of ∼30000AU in size, separated by ∼50000AU. The groups
coincide with dust column density peaks detected by Herschel. These
results show hierarchical, two-mode fragmentation in which the
maternal filament periodically fragments into groups of dense cores.
Critically, our results indicate that the fragmentation models for
lower line-mass filaments (∼16M☉/pc) fail to capture the
observed properties of the ISF. We also find that the protostars
identified with Spitzer and Herschel in the ISF are grouped at
separations below ∼17000AU. In contrast, young stars with disks do not
show significant grouping. This suggests that the grouping of dense
cores is partially retained over the protostar lifetime, but not over
the lifetime of stars with disks. This is in agreement with a scenario
where protostars are ejected from the maternal filament by the
slingshot mechanism, a model recently proposed for the ISF. The
separation distributions of the dense cores and protostars may also
provide an evolutionary tracer of filament fragmentation.
Description:
We used the ALMA interferometer during Cycle 2 to observe the northern
part of the ISF at 3mm continuum emission and C18O line emission
(ESO Project ID 2013.1.01114.S, PI Kainulainen). In this paper we only
use the continuum emission data. Both the 12-m and the 7-m (Atacama
Compact Array; ACA) arrays were employed. The 7-m array observations
were conducted on 16th August 2014 and the 12-m array observations in
a compact configuration on 16th January 2015.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
05 35 17.3 -05 23 28 Orion A = M 42
-----------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 147 1 Information on FITS image
isf-3mm.fits 2880 2230 FITS image
--------------------------------------------------------------------------------
See also:
J/ApJ/566/974 : CHANDRA obs. of YSOs in OMC-2 and OMC-3 (Tsujimoto+, 2002)
J/AJ/125/1537 : QUIRC Chandra sources in OMC 2/3 (Tsujimoto+, 2003)
J/ApJ/716/893 : Polarisation at 850mu{m} in OMC-2 and OMC-3 (Poidevin+, 2010)
J/A+A/556/A57 : Transitions in OMC-2 FIR 4 in the far-IR (Kama+, 2013)
J/A+A/588/A30 : Properties of cores in OMC 2/3 (Sadavoy+, 2016)
J/A+A/596/A26 : OMC-2 FIR 3 and FIR 4 [OI] maps (Gonzalez-Garcia+, 2016)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 27 I4 --- Ny Number of pixels along Y-axis
29- 51 A23 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.sss)
53- 59 F7.3 GHz Freq Observed frequency
61- 64 I4 Kibyte size Size of FITS file
66- 77 A12 --- FileName Name of FITS file
79-147 A69 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Jouni Kainulainen, jtkainul(at)mpia.de
(End) Patricia Vannier [CDS] 26-Apr-2017