J/A+A/620/A27 Taurus ultra-wide pairs. II. (Joncour+, 2018)
Multiplicity and clustering in Taurus star forming region.
II. From ultra-wide pairs to dense NESTs
Joncour I., Duchene G., Moraux E., Motte F.
<Astron. Astrophys. 620, A27 (2018)>
=2018A&A...620A..27J 2018A&A...620A..27J (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Stars, double and multiple
Keywords: methods: statistical - binaries: visual -
open clusters and associations: individual: Taurus - ISM: structure -
stars: formation
Abstract:
Multiplicity and clustering of young pre-main sequence stars appear as
critical clues to understand and constrain the star formation process.
Taurus is the archetypical example of the most quiescent star forming
regions that may still retain primeval signatures of star formation.
This work identifies local overdense stellar structures as a critical
scale between wide pairs and loose groups in Taurus.
Using the density-based spatial clustering of applications with noise
(dbscan) algorithm, and setting its free parameters based on the
one-point correlation function and the k-nearest neighbor statistics,
we have extracted reliably overdense structures from the sky-projected
spatial distribution of stars.
Nearly half of the entire stellar population in Taurus is found to be
concentrated in 20 very dense, tiny and prolate regions called NESTs
(for Nested Elementary STructures). They are regularly spaced (∼2pc)
and mainly oriented along the principal gas filaments axes. Each NEST
contains between four and 23 stars. Inside NESTs, the surface density
of stars may be as high as 2500pc-2 and the mean value is
340pc-2. Nearly half (11) of these NESTs contain about 75% of the
class 0 and I objects. The balance between Class I, II, and, III
fraction within the NESTs suggests that they may be ordered as an
evolutionary temporal scheme, some of them getting infertile with
time, while other still giving birth to young stars. We have inferred
that only 20% of stars in Taurus do not belong to any kind of stellar
groups (either multiple system, ultra wide pairs or NESTs). The
mass-size relation for stellar NESTs is very close to the
Bonnor-Ebert expectation. The range in mass is about the same as
that of dense molecular cores. The distribution in size is bimodal
peaking at 12.5 and 50kAU and the distribution of the number of YSOs
in NESTs as a function of size exhibits two regimes.
We propose that the NESTs in their two size regimes represent the
spatial imprints of stellar distribution at birth as they may have
emerged within few millions years from their natal cloud either from a
single core or from a chain of cores. We have identified them as the
preferred sites of star formation in Taurus. These NESTs are the
regions of highest stellar density and intermediate spatial scale
structures between ultra-wide pairs and loose groups.
Description:
The catalogue of young stars located in NESTs within the Taurus star
forming region. The NEST, stands for Nested Elementary STrucures, are
high stellar density regions detected with a high reliability above
random expectations using dbscan algorithm and nearest neighbor
statistics. As much as nearly half the stellar population of Taurus
are located in those NESTs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 76 151 Young stars in NESTs (Taurus)
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See also:
J/AJ/135/2496 : Near-IR survey of Class I protostars (Connelley+, 2008)
J/ApJS/186/111 : Spitzer observations of Taurus members (Luhman+, 2010)
J/ApJS/186/259 : Taurus Spitzer survey: new candidate members (Rebull+, 2010)
J/ApJ/731/8 : Multiple star formation in Taurus-Auriga (Kraus+, 2011)
J/ApJ/727/64 : Young stellar groups 7 their most massive stars (Kirk+, 2011)
J/ApJ/757/141 : Companion IR detection limits in young associations
(Kraus+, 2012)
J/ApJ/784/126 : Infrared photometry of all known members in Taurus
(Esplin+, 2014)
J/ApJ/799/155 : Sub-stellar companions in Taurus (Daemgen+, 2015)
J/A+A/599/A14 : Taurus ultra-wide pairs (Joncour+, 2017)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/151] Index number of star in NESTs
5- 6 I2 --- NEST [1/20] Identification number of NEST structure
8- 24 A17 --- 2MASS 2MASS ID (star)
26- 44 A19 --- Name Name (Star)
46- 51 F6.3 deg RAdeg Right ascension (J2000)
53- 58 F6.3 deg DEdeg Declination (J2000)
60- 64 A5 --- SpType Spectral Type of (primary) star
66- 70 F5.3 Msun Mass Mass of the (primary) star
72- 74 A3 --- Class Class of the (primary) star
76 I1 --- Nstar Total number of star included in the system
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Acknowledgements:
Isabelle Joncour, isabelle.joncour(at)univ-grenoble-alpes.fr
References:
Joncour et al., Paper I 2017A&A...599A..14J 2017A&A...599A..14J, Cat. J/A+A/599/A14
(End) Isabelle Joncour [Univ. Grenoble Alpes] Patricia Vannier [CDS] 28-Sep-2018