J/ApJ/871/46 Hectoschelle spectra of 2MASS stars in Cep OB3b (Karnath+, 2019)
The dynamics, structure, and fate of a young cluster during gas dispersal:
Hectoschelle, Chandra, Spitzer, and Gaia observations of Cep OB3b.
Karnath N., Prchlik J.J., Gutermuth R.A., Allen T.S., Megeath S.T.,
Pipher J.L., Wolk S., Jeffries R.D.
<Astrophys. J., 871, 46-46 (2019)>
=2019ApJ...871...46K 2019ApJ...871...46K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open; Spectra, optical; Radial velocities;
Infrared sources; Binaries, spectroscopic
Keywords: open clusters and associations: Cep OB3b
stars: formation; stars: kinematics and dynamics
stars: pre-main sequence; techniques: radial velocities
Abstract:
We present a study of the kinematics and structure of the Cep OB3b
cluster based on new spectra obtained with the Hectoschelle
spectrograph on the MMT and data from Spitzer, Chandra, and Gaia. At a
distance of 819±16pc, Cep OB3b is one of the closest examples of a
young (∼3-5Myr), large (∼3000 total members) cluster at the late
stages of gas dispersal. The cluster is broken into two subclusters
surrounded by a lower density halo. We fit the empirical density law
of King to each subcluster to constrain their sizes and structure. The
richer eastern subcluster has circular symmetry, a modest central
density, and lacks molecular gas toward its core, suggesting it has
undergone expansion due to gas dispersal. In contrast, the western
subcluster deviates from circular symmetry, has a smaller core size,
and contains significant molecular gas near its core, suggesting that
it is in an earlier phase of gas dispersal. We present posterior
probability distributions for the velocity dispersions from the
Hectoschelle spectra. The east will continue to expand and likely form
a bound cluster with ∼35% of stars remaining. The west is undergoing
slower gas dispersal and will potentially form a bound cluster with
∼75% of stars remaining. If the halo dissipates, this will leave two
independent clusters with ∼300 members; proper motions suggest that
the two subcluster are not bound to each other.
Description:
The spectra were obtained on the MMT with Hectoschelle (R∼32000). Five
epochs of observations were taken over five years (2009-2013). These
spectra span 150Å centered on Hα at 6563Å.
The target stars are from the combined visible, infrared, and X-ray
study of Allen+ (2012, J/ApJ/750/125).
A total of 561 spectra (over five epochs; see Tables 2-6) were taken
toward Cep OB3b of 499 distinct stars, 190 of which were identified as
members.
Objects:
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RA (ICRS) DE Designation(s)
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22 55 31.19 +62 38 54.1 Cep OB3b = NAME Ass Cep OB 3
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 62 120 2009-Oct-26 RV results
table3.dat 62 123 2009-Nov-03 RV results
table4.dat 62 88 2010 RV results
table5.dat 62 152 2011 RV results
table6.dat 62 77 2013 RV results
table7.dat 56 99 Potential spectroscopic binary candidates
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See also:
VI/120 : High-resolution synthetic stellar library (Coelho+, 2005)
J/MNRAS/341/805 : UBVI CCD photometry of Cep OB3b (Pozzo+, 2003)
J/AJ/129/363 : Spectroscopy in Orion Nebula Cluster (Sicilia-Aguilar+, 2005)
J/AJ/129/829 : Hα emission stars in NGC 2264 (Dahm+, 2005)
J/A+A/442/1127 : Library of 2500-10500Å synthetic spectra (Munari+, 2005)
J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)
J/MNRAS/375/1220 : BVI photometry of young stars in 10 clusters (Mayne+, 2007)
J/ApJ/676/1109 : Velocities of stars in the ONC (Furesz+, 2008)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/697/1103 : Kinematics of Orion Nebula Cluster (Tobin+, 2009)
J/ApJ/699/1454 : YSOs around Cepheus B (Getman+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/MNRAS/403/545 : Young stars in Cepheus OB3b (Littlefair+, 2010)
J/ApJ/750/125 : Spitzer imaging of Cepheus OB3b cluster (Allen+, 2012)
J/A+A/563/A94 : Kinematics of the Gamma Vel cluster (Jeffries+, 2014)
J/ApJ/786/113 : Extinction law in the Cep OB3b young cluster (Allen+, 2014)
J/ApJ/787/107 : Spatial structure of young stellar clusters. I. (Kuhn+, 2014)
J/ApJ/794/124 : Star forming region NGC 2264 Spitzer sources (Rapson+, 2014)
J/ApJ/799/136 : IN-SYNC. II. Candidate young stars in NGC 1333 (Foster+, 2015)
J/AJ/149/119 : Radial velocities of stars in NGC 2264 (Tobin+, 2015)
J/ApJ/807/27 : IN-SYNC. III. RVs of IC348 stars (Cottaar+, 2015)
J/ApJ/821/8 : Sp. binary population of ONC and NGC2264 (Kounkel+, 2016)
J/A+A/601/A97 : Gaia-ESO Survey: Cha I members (Sacco+, 2017)
J/ApJ/844/138 : Optical spectroscopy toward Orion B fields (Kounkel+, 2017)
J/ApJ/865/73 : GOBELINS. V. Kinematics of Perseus (Ortiz-Leon+, 2018)
J/ApJ/870/32 : Kinematics in young star clusters & associations (Kuhn+, 2019)
Byte-by-byte Description of file: table[2-7].dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS identifier (JHHMMSSss+DDMMSSs)
19- 20 I2 h RAh [22] Hour of right ascension (J2000)
22- 23 I2 min RAm Minute of right ascension (J2000)
25- 29 F5.2 s RAs Second of right ascension (J2000)
31 A1 --- DE- [+] Sign of declination (J2000)
32- 33 I2 deg DEd [62/63] Degree of declination (J2000)
35- 36 I2 arcmin DEm Arcminute of declination (J2000)
38- 42 F5.2 arcsec DEs Arcsecond of declination (J2000)
44- 50 F7.2 km/s RV [-122/58]? Radial velocity
52- 56 F5.2 km/s e_RV [0.19/30]? RV uncertainty
58- 62 F5.2 --- R [0.03/21.2]? R value (not for Table 7) (1)
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Note (1): The R value corresponds to the quality of the cross-correlation and
scales as R=h/(2σa)0.5, where h is the height of the
cross-correlation peak, and σa is the estimated uncertainty
from the rms of the antisymmetric portion of the correlation function.
See Section 3.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 20-Oct-2023