J/ApJ/438/813 Stellar population in ρ Oph cloud core (Strom+, 1995)
The evolutionary status of the stellar population in the ρ Ophiuchi
cloud core
STROM K.M., KEPNER J., STROM S.E.
<Astrophys. J. 438, 813 (1995)>
=1995ApJ...438..813S 1995ApJ...438..813S (SIMBAD/NED BibCode)
ADC_Keywords: Regional catalog; Positional data; Photometry, infrared;
Cross identifications
Keywords: circumstellar matter - infrared: stars -
ISM: individual (ρ Ophiuchi) -
stars: luminosity function, mass function -
stars: pre-main-sequence - surveys
Abstract:
This contribution reports the results of an infrared imaging survey
aimed at characterizing the stellar populations associated with the
three densest star-forming cores in the Ophiuchus molecular cloud
complex. The survey has sufficient sensitivity at J, H, and K (at
5σ limits of 16.5, 15.4 and 14.2) to provide a complete census
of embedded young stellar objects (YSOs) with masses greater than the
hydrogen-burning limit, provided that their ages are less than 3 Myr
and that they are obscured by no more than ∼18 mag of visual
extinction. Our data suggest (1) a large fraction (>70%) of the
sources located within the cores are still surrounded by circumstellar
disks and/or envelopes; and (2) the shape of the initial mass function
for masses, M<1Msun, appears to be consistent with that derived from
the solar neighborhood. We also report the results of a deeper imaging
survey of centimeter continuum sources (14 sources) in these
star-forming cores and in the larger Ophiuchus complex (eight
sources). A large fraction 11/14) of the radio sources associated with
the cores appear to have infrared excesses diagnostic of circumstellar
accretion disks and/or infalling circumstellar envelopes. In these
cases, the centimeter continuum radiation most likely diagnoses the
ionized component of energetic winds or jets which characterize YSOs
during the disk accretion phase. By contrast, of the eight radio
sources located outside dense cores, only two show infrared excesses.
For the sources which lack infrared excesses, the centimeter continuum
emission is probably produced by gyrosynchrotron radiation arising in
the stellar magnetospheres of weak emission T Tauri stars.
There is some evidence that the frequency of binary companions among
the sample of centimeter continuum sources in the molecular cores may
be higher (by as much as a factor of 3-4) than that among the older,
distributed population of young stars in the larger Ophiuchus cloud
complex.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1 81 52 Photometry data from the SQIID Mosaic
table2 69 52 Derived values from the SQIID data
table3 80 67 Data for stars with photometry of lower
accuracy
table4 86 93 Infrared data for the ρ Ophiuchi cloud
VLA sources
table6 72 5 Multiplicity measures of VLA sources
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Table 5: Identified pairs in the VLA sample (LFAM: Leous et al. 1991)
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Primary Secondary Sep. AK Core
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LFAM 2 LFAM 1 9"7 3.8 A
S 2 LFAM 3 10"6 3.1 A
LFAM 5 LFAM 4 9"7 A
LFAM 9SW LFAM 9NE 1"2 0.5 A
LFAM 15N LFAM 15S 6"3 0.05 A
LFAM 33 LFAM 33N 7"3 2.75 E/F
LFAM 30E LFAM 30W 3"3 0.3 E/F
LFAM 30S 3"9 2.5 E/F
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Multiple VLA Sources in Cores Outside the LFAM Survey
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WL 5 YLW 12A 6"5 1.1 B
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Multiple VLA Sources in All Cores with Separation Below 1"
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S1 A S1 B 0"02 1.8 A
SR 12A SR 12B 0"30 0.1 E/F
VSSG 14A VSSG 14B 0"10 0.8 B
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Byte-by-byte Description of file: table1 table3
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (1950)
4- 5 I2 min RAm Right ascension (1950)
7- 10 F4.1 s RAs Right ascension (1950)
14 A1 --- DE- Declination sign
15- 16 I2 deg DEd Declination (1950)
18- 19 I2 arcmin DEm Declination (1950)
21- 22 I2 arcsec DEs Declination (1950)
25- 29 F5.2 mag Kmag K magnitude
32- 35 F4.2 mag e_Kmag ? Error on K magnitude
37 A1 --- l_J-H [><] Limit flag on J-H
38- 41 F4.2 mag J-H ? J-H colour index
42 A1 --- n_J-H [b] See Note (1)
44- 47 F4.2 mag e_J-H ? Error on J-H
51 A1 --- l_H-K [><] Limit flag on H-K
52- 55 F4.2 mag H-K ? H-K colour index
56 A1 --- n_H-K [b] See Note (1)
58- 61 F4.2 mag e_H-K ? Error on H-K
64- 66 A3 --- Core Dense molecular core association (2)
69- 71 A3 --- Type Type of stars (3)
73 A1 --- n_Id [a] See Note (4)
74- 81 A8 --- Id Identification
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Note (1): When 'b': This object falls on a small gap in the H mosaic.
J=16.15±0.20.
Note (2): A = Oph A
B = Oph B
E/F= Oph E/F
Note (3): P= Photospheric; Stars which fall within the domain of the normal,
reddened main-sequence dwarfs
D= Disk; Stars which fall redward of the reddening vector extending
from the latest main-sequence dwarfs but blueward of the reddening
vector extending upward from the reddest colors predicted for
an optically thick, physically thin accretion disk
E= Envelope; Stars which lie rightward of reddened accretion disk
colors
Stars which lie within 1σ of a domain boundary are denoted
P/D or D/E.
Note (4): When 'a': These objects are nebulous, and the photometric center
shifts with wavelengths
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (1950)
4- 5 I2 min RAm Right ascension (1950)
7- 10 F4.1 s RAs Right ascension (1950)
14 A1 --- DE- Declination sign
15- 16 I2 deg DEd Declination (1950)
18- 19 I2 arcmin DEm Declination (1950)
21- 22 I2 arcsec DEs Declination (1950)
25- 28 F4.2 mag J10 ? Derived reddening-corrected absolute
J magnitude
31- 34 F4.2 mag A1J ? Extinction A1J (1)
37- 40 F4.2 mag J20 ? Reddening-corrected absolute
J magnitude (2)
43- 46 F4.2 mag A2J ? Extinction A2J (2)
49 A1 --- l_Mass0.3 Limit flag on mass
50- 53 F4.2 solMass Mass0.3 ? Mass derived from D'Antona and
Mazzitelli (1994) tracks assuming a cluster
age of 0.3Myr
54 A1 --- n_Mass0.3 [f] foreground
55 A1 --- l_Mass1 Limit flag on mass
56- 59 F4.2 solMass Mass1 ? Mass derived from D'Antona and
Mazzitelli (1994) tracks assuming a cluster
age of 1Myr
60 A1 --- n_Mass1 [f] foreground
62- 69 A8 --- Id Identification
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Note (1): Derived from the (J-H), (H-K) diagram for stars whose reddened
colours place them within the domain occupied by stars surrounded by
accretion disk
Note (2): Derived from the J, (J-H) color-magnitude diagram for objects
which lie within the domain occupied by normal reddening stars;
an isochrone corresponding to an age of 0.3Myr is assumed in
estimating A2J
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Byte-by-byte Description of file: table4
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Bytes Format Units Label Explanations
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1- 8 A8 --- Object Object
11 A1 --- l_Jmag [>] Limit flag on J magnitude
12- 16 F5.2 mag Jmag ? J magnitude
17 A1 --- q_Jmag [ABCD] Error on J magnitude (1)
19 A1 --- l_Hmag [>] Limit flag on H magnitude
20- 24 F5.2 mag Hmag ? H magnitude
25 A1 --- q_Hmag [ABCD] Error on H magnitude (1)
28 A1 --- l_Kmag [>] Limit flag on Kmag
29- 33 F5.2 mag Kmag ? K magnitude
34 A1 --- q_Kmag [ABCD] Error on K magnitude (1)
36 A1 --- l_L'mag Limit flag on L' magnitude
37- 41 F5.2 mag L'mag ? L' magnitude
42 A1 --- q_L'mag [ABCD] Error on L' magnitude (1)
43 A1 --- l_Mmag [>] Limit flag on Mmag
44- 48 F5.2 mag Mmag ? M magnitude
49 A1 --- q_Mmag [ABCD] Error on M magnitude (1)
51 A1 --- l_J-H [>] Limit flag on J-H
52- 56 F5.2 mag J-H ? J-H colour index
57 A1 --- u_J-H Uncertainty flag on J-H
58 A1 --- l_H-K [>] Limit flag on H-K
59- 62 F4.2 mag H-K ? H-K colour index
63 A1 --- u_H-K Uncertainty flag on H-K
64 A1 --- l_K-L' [><] Limit flag on K-L'
65- 68 F4.2 mag K-L' ? K-L' colour index
69 A1 --- u_K-L' Uncertainty flag on K-L'
71- 74 F4.2 mag K-M ? K-M colour index
75 A1 --- u_K-M Uncertainty flag on K-M
77- 87 A11 --- Notes Notes (2)
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Note (1): The quality index is defined as:
A, uncertainty <10%;
B, uncertainty between 10 and 20%;
C, uncertainty between 20 and 30%;
D, the uncertainty is probably larger than 30%, not due to photon
statistics, but due to other problems such as close companions
and problems dealing with a very nonflat background.
Note (2): Keys to notes:
(1): Objects 1 and 2 correspond to GSS 30 NIRS 3 and 2 of Tamura et
al. 1991. They lie within the reflection nebulosity surrounding
GSS 30 complicating measurement of the fluxes attributable to
these objects. They are separated by 11"6. Object 2 is also
IRS 2 of Castelaz et al.1985
(2): Reflection nebulosity is associated with this object. A bright
star (K=7.3) lies 10"4 away at P.A. 145deg
(3): This pair is separated by 1"15 at P.A. 67deg
(4): This object illuminates a large reflection nebulosity in the
near-infrared as well as on the POSS red plate
(5): These objects are separated by 6"3 at P.A. 170deg. The northern
object lies nearest to the VLA position
(6): The L' and M magnitudes were measured on the night following
the J, H, and K measurements
(7): The lunar occultation observation of Simon et al. 1987 and the
speckle observations of Zinnecker, Chelli & Perrier 1987 require
two components. The best-fit model of Simon et al.1987 requires
85% of the light at K in an object of 7.1 mas diameter and 15%
of the light in a halo of 415 mas diameter. A reflection nebula
is associated with this object
(8): This object resolves into a close triple. 30W is at 3.3" at
P.A. 269deg from 30E. 30S is at 3.9" at P.A.232deg from 30E.
Both Barsony et al 1989 and Rieke, Ashok, & Boyle 1989 had found
this object to be double
(9): This object also illuminates a reflection nebula. The secondary
lies at 7.3" at P.A. 323deg
(10): Owing to a slight telescope drift, this northern component only
appeared in the L' and M frames of object 33. However, the
J, H, and K magnitudes can be measured on our SQIID frames.
Those values are given here for completeness
(11): Lunar occultation studies (Simon et al.1987) have resolved this
object. No Fresnel interference was seen; this object could
be modeled with geometrical optics. A satisfactory fit to the
observations could be made with a uniformly illuminated object
of ∼0.5" extent. This object illuminates a reflection nebula;
the nearest neighbors of this object lie at 26.2" at PA 48deg
(K=10.6) and 23.3" at P.A. 297deg (K=10.5). This nebulosity and
the companions have been discussed by Zinnecker 1989.
The polarization of the nebulosity has been studied by Aspin,
Casali & Walther 1989
(12): These objects have been detected in previous VLA surveys of the
ρ Oph cloud and are also located in core regions. They are
included here as we obtained new data over the full wavelength
range
(13): Also known as El 27 and is a 3 in the list of LFAM (Leous et
al. 1991)
(14): Denoted a6 in the list of LFAM (Leous et al. 1991)
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Byte-by-byte Description of file: table6
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Bytes Format Units Label Explanations
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1- 47 A47 --- Sample Sample
50- 53 F4.2 --- mf Multiplicy frequency (1)
56- 59 F4.2 --- cp Companion probability (2)
62- 65 F4.2 --- pf Pairing factor (3)
67- 68 I2 --- N Number of sources
72 I1 --- Notes ? Notes (4)
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Note (1): Defined as the ratio between the number of multiple systems detected
and the number of all objects (single+multiple) observed. See
Appendix in the paper
Note (2): Defined as the ratio between the number of stellar components
in multiple systems and the number of stellar components in all
objects observed. See Appendix in the paper
Note (3): Defined as the ratio between the number of pair and the number of
multiple systems. See Appendix in the paper
Note (4): Keys to notes:
1: N is the number of sources imaged at the Infrared Telescope
Facility which were bright enough at K to allow a companion
fainter by at least 3 mag to be detected
2: While there are 35 sources in the LFAM 5sigma sample, four of
these can be found in two pairs using our definition Of pairs.
Therefore the total sample must be reduced by two systems
3: Four of the LFAM sources fall along a line centered on a source
which they feel is a background galaxy. These objects have been
eliminated from this sample as they are probable background objects
4: This sample includes the eight 3σ near-infrared identified
objects while eliminating the probable background objects
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References:
Aspin C., Casali M.M., Walther D.M. 1989, in Proc. ESO Workshop on Low-Mass
Star Formation and Pre-Main-Sequence Objects, ed. B. Reipurth (Garching:
European Southern Obs.), 349
Barsony M. et al. 1989, ApJ 346, L93
Castelaz M.W. et al. 1985, ApJ 290, 261
D'Antona F. and Mazzitelli I. 1994, ApJS 90, 467
Leous J.A. et al. 1991, ApJ 379, 683 (LFAM)
Rieke G.H., Ashok N.M., Boyle R.P. 1989, ApJ 339, L71
Simon M. et al. 1987, ApJ 320, 344
Tamura M. et al. 1991, ApJ 378, 611
Zinnecker H. 1989, in Proc. ESO Workshop on Low-Mass Star Formation and
Pre-Main-Sequence Objects, ed. B. Reipurth (Garching: European Southern
Obs.), 447
Zinnecker H., Chelli A., Perrier C. 1987, in IAU Symp. 115, Star Forming
Regions, ed. M. Peimbert and J. Jugako (Dordrecht: Reidel), 71
Historical Notes: Keypunched at CDS
(End) James Marcout, Simona Mei [CDS] 08-Aug-1995