J/ApJ/819/143 HCO+ and N2D+ dense cores in Perseus (Campbell+, 2016)
Contraction signatures toward dense cores in the Perseus molecular cloud.
Campbell J.L., Friesen R.K., Martin P.G., Caselli P., Kauffmann J.,
Pineda J.E.
<Astrophys. J., 819, 143 (2016)>
=2016ApJ...819..143C 2016ApJ...819..143C (SIMBAD/NED BibCode)
ADC_Keywords: Radio lines ; Molecular clouds ; Velocity dispersion ;
Interstellar medium
Keywords: ISM: individual: Perseus; ISM: jets and outflows;
ISM: kinematics and dynamics; ISM: molecules;
radio lines: ISM; stars: formation
Abstract:
We report the results of an HCO+ (3-2) and N2D+ (3-2) molecular
line survey performed toward 91 dense cores in the Perseus molecular
cloud using the James Clerk Maxwell Telescope, to identify the
fraction of starless and protostellar cores with systematic radial
motions. We quantify the HCO+ asymmetry using a dimensionless
asymmetry parameter δv, and identify 20 cores with significant
blue or red line asymmetries in optically thick emission indicative of
collapsing or expanding motions, respectively. We separately fit the
HCO+ profiles with an analytic collapse model and determine
contraction (expansion) speeds toward 22 cores. Comparing the
δv and collapse model results, we find that δv is a
good tracer of core contraction if the optically thin emission is
aligned with the model-derived systemic velocity. The contraction
speeds range from subsonic (0.03km/s) to supersonic (0.40km/s), where
the supersonic contraction speeds may trace global rather than local
core contraction. Most cores have contraction speeds significantly
less than their free-fall speeds. Only 7 of 28 starless cores have
spectra well-fit by the collapse model, which more than doubles (15 of
28) for protostellar cores. Starless cores with masses greater than
the Jeans mass (M/MJ>1) are somewhat more likely to show contraction
motions. We find no trend of optically thin non-thermal line width
with M/MJ, suggesting that any undetected contraction motions are
small and subsonic. Most starless cores in Perseus are either not in a
state of collapse or expansion, or are in a very early stage of
collapse.
Description:
Table 1 summarizes the 91 dense cores observed, with their Right
Ascension and Declination pointing positions.
Pointed observations of the Perseus cores were performed using the
James Clerk Maxwell Telescope (JCMT). Targets were observed in the
HCO+ (3-2) and N2D+ (3-2) rotational transitions in position-switching
mode, with assumed rest frequencies of 267.557619GHz and
231.321665GHz, respectively. The spectral resolution was 30.5kHz,
corresponding to a velocity resolution of 0.03km/s for HCO+ (3-2) and
0.04km/s for N2D+ (3-2). Observations were conducted between 2007
September and 2009 September.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 66 91 Summary of observations
table2.dat 119 30 *Summary of Perseus dense core kinematics
table4.dat 44 58 Continuum masses and stability of the Perseus cores
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Note on table2.dat: Hyperfine structure in NH3 allows for very accurate
velocity measurements (see Rosolowsky et al. 2008, J/ApJS/175/509
for details).
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See also:
J/ApJS/220/11 : SEDs of Spitzer YSOs in the Gould Belt (Dunham+, 2015)
J/ApJ/786/29 : Catalog of distances to molecular clouds (Schlafly+, 2014)
J/MNRAS/402/603 : SCUBA cores in Perseus mol. cloud (Curtis+, 2010)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/696/298 : Dense cores in Perseus (Foster+, 2009)
J/ApJ/692/973 : Protostars in Perseus, Serpens and Ophiuchus (Enoch+, 2009)
J/ApJS/175/509 : Ammonia spectral atlas in Perseus (Rosolowsky+, 2008)
J/A+A/472/187 : submm cores in Perseus (Hatchell+, 2007)
J/ApJ/668/1042 : Dense cores in Perseus molecular cloud (Kirk+, 2007)
J/ApJ/646/1009 : Structures of dust in Perseus molecular cloud (Kirk+, 2006)
J/ApJ/638/293 : 1.1mm sources in the Perseus Molecular Cloud (Enoch+, 2006)
J/ApJS/125/161 : A database of dense cores mapped in ammonia (Jijina+, 1999)
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Name Source designation (1)
6- 10 A5 --- f_Name [ ,b-f] Flag(s) on Name (2)
12- 14 I3 --- Bolo [1/121]? Bolo number
(<[EYG2006] Bolo NNN> in Simbad)
16 I1 h RAh Hour of right ascension (J2000)
18- 19 I2 min RAm Minute of right ascension (J2000)
21- 24 F4.1 s RAs Second of right ascension (J2000)
26 A1 --- DE- Sign of declination (J2000)
27- 28 I2 deg DEd Degree of declination (J2000)
30- 31 I2 arcmin DEm Arcminute of declination (J2000)
33- 36 F4.1 arcsec DEs Arcsecond of declination (J2000)
38- 42 F5.2 K Tpk1 [0.4/10.7]? HCO+ peak temperature
44- 47 F4.2 K rms1 [0.08/1.3] HCO+ rms
49- 52 F4.2 --- Tpk2 [0.4/2.1]? N2D+ peak temperature
53 A1 --- f_Tpk2 [f] Flag on Tpk2 (2)
55- 58 F4.2 --- rms2 [0.07/0.4]? N2D+ rms
60 A1 --- Proto Protestellar? (Y or N)
62- 66 A5 --- Ref ID reference (3)
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Note (1): Names as given in JCMT proposal ID M07BU33 and the archive of
the spectral data
(http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/jcmt/).
S# indicate target first identified in JCMT dust maps obtained with
SCUBA (Kirk et al. 2006, J/ApJ/646/1009;
<[KJD2006] SMM JHHMMmm+DDMMm> in Simbad)
D# for objects from a list prepared from the far-infrared-based
dust map produced by Schnee et al. (2008ApJ...684.1228S 2008ApJ...684.1228S)
See section 2 for further explanations.
Note (2): Flag as follows:
b = Classified as protostellar based on the detection of associated outflows,
despite lacking infrared point-source detections.
c = HCO+ (3-2) line profiles too complex for the analysis in this paper.
d = Systemic velocity sufficiently aligned with brightest HCO+ peak
(Section 4).
e = More than one nearby (<40") YSO (Section 2).
f = More than one dense core along the line of sight (Section 4).
Note (3): Letters of the YSO reference ID designating their catalog source:
J = Jorgensen et al. (2007ApJ...656..293J 2007ApJ...656..293J; <[JJK2007] NN> in Simbad),
E = Enoch et al. (2009, J/ApJ/692/973; <[EES2009] Per-emb NN> in Simbad),
D = Dunham et al. (2015, J/ApJS/220/11),
C = Chen et al. (2010ApJ...715.1344C 2010ApJ...715.1344C),
P = Pineda et al. (2011ApJ...743..201P 2011ApJ...743..201P),
S = Schnee et al. (2012ApJ...745...18S 2012ApJ...745...18S)
and associated source number in that catalog where applicable.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Name Source designation
6 A1 --- f_Name Flag on Name (1)
8- 14 F7.4 km/s Vthin [3.5/10.3] N2D+/N2H+/NH3 systemic velocity
16- 21 F6.4 km/s e_Vthin [0/0.1] Vthin uncertainty
23- 28 F6.4 km/s Sthin [0.1/0.7] N2D+/N2H+/NH3 velocity dispersion
30- 35 F6.4 km/s e_Sthin [0/0.09] Sthin uncertainty
37 A1 --- r_OID Reference ID (2)
38- 40 I3 --- OID ? Number identifier in Ref
42- 47 F6.3 km/s Vmod [4/10.1]? HCO+ HILL5 model-derived systemic
velocity
49- 53 F5.3 km/s e_Vmod [0.007/0.03]? Vmod uncertainty
55- 59 F5.3 km/s Sigma [0.1/0.6]? HCO+ HILL5 velocity dispersion
61- 65 F5.3 km/s e_Sigma [0.005/0.08]? Sigma uncertainty
67- 71 F5.2 km/s Vin [-0.6/0.4]? HCO+ HILL5 contraction velocity (3)
73- 76 F4.2 km/s e_Vin [0.01/0.2]? Vin uncertainty
78- 81 F4.1 K Tex [6.8/19.1]? HCO+ HILL5 excitation temperature
83- 85 F3.1 K e_Tex [0.1/0.8]? Tex uncertainty
87- 89 F3.1 --- tau [0.8/7]? HCO+ HILL5 optical depth
91- 93 F3.1 --- e_tau [0.1/0.8]? tau uncertainty
95- 97 F3.1 --- Chi2 [0.7/5.3]? HCO+ HILL5 reduced χ2 goodness
of fit parameter
99-103 F5.2 --- delV [-1.2/0.9]? Dimensionless asymmetry parameter
(δv) (4)
105-108 F4.2 --- e_delV [0.01/0.2]? delV uncertainty
110-114 F5.2 --- delV* [-1.2/1]? Modified asymmetry parameter (5)
116-119 F4.2 --- e_delV* [0.02/0.3]? delV* uncertainty
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Note (1): Flag as follows:
b = Broad line wings in HCO+ profiles fit by a Gaussian and removed before
modeling with HILL5 (Section 4.2).
c = Low S/N N2D+ source (Section 4.1).
Note (2): Letters of the optically thin reference ID designating the catalog
source as follows:
K = N2H+ (Kirk et al. 2007, J/ApJ/668/1042; <[KJT2007] NNN> in Simbad) and
R = NH3 (Rosolowsky et al. 2008, J/ApJS/175/509;
<[RPF2008] NH3SRC NNN> in Simbad) surveys
Note (3): Negative contraction velocities (Vin<0) imply outward motions.
Note (4): Mardones et al. (1997ApJ...489..719M 1997ApJ...489..719M) defined a dimensionless
asymmetry parameter to quantify asymmetries in multi-peaked line
profiles: Equation (1):
δv=(Vthick-Vthin)/ΔVthin
where blue asymmetries (δv<0) identify candidate dense cores
undergoing collapse. Here Vthick is the line of sight velocity of
the brightest component in the optically thick line profile, Vthin
is the line of sight velocity of the optically thin line tracing the
systemic velocity of the dense core, and ΔVthin is the full
width at half maximum (FWHM) of the optically thin line.
See section 1.
Note (5): This modified asymmetry parameter replaces the systemic velocity
Vthin with the HILL5 model-derived systemic velocity Vmod in
Equation (1). See section 5.1.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Set "Starless" or "Protostellar"
14- 17 A4 --- Name Source designation or "Mean"
19- 22 F4.2 pc Reff [0.01/0.2] Effective core radius from the
continuum surveys
24- 26 F3.1 Msun Mass [0.2/7.2] Derived core mass
28- 31 F4.1 K Tk [9/16.4] Gas kinetic temperature (1)
33- 36 F4.2 km/s SigNT [0.08/0.5]? Non-thermal velocity dispersion
38- 40 F3.1 Msun MJ [0.5/3.7] Jeans mass
42- 44 F3.1 --- M/MJ [0.2/5.8] Ratio of core mass to Jeans mass
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Note (1): For cores with no overlap with
Rosolowsky et al. (2008, J/ApJS/175/509), we set Td=11K, the mean
TK for all detected cores in Perseus.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 26-May-2016