J/A+A/573/A19 Cep OB2 Herschel/PACS view (Sicilia-Aguilar+, 2015)
The Herschel/PACS view of the Cep OB 2 region:
Global protoplanetary disk evolution and clumpy star formation.
Sicilia-Aguilar A., Roccatagliata V., Getman K., Riviere-Marichalar P.,
Birnstiel T., Merin B., Fang M., Henning T., Eiroa C., Currie T.
<Astron. Astrophys., 573, A19-19 (2015)>
=2015A&A...573A..19S 2015A&A...573A..19S
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ;
Millimetric/submm sources ; Accretion
Keywords: stars: pre-main sequence - protoplanetary disks - stars: formation -
open clusters and associations: individual: Cep OB2 -
circumstellar matter - stars: individual: HD 206267
Abstract:
The CepOB2 region, with its two intermediate-aged clusters Tr37 and
NGC7160, is a paradigm of sequential star formation and an ideal site
for studies of protoplanetary disk evolution. We use Herschel data to
study the protoplanetary disks and the star formation history of the
region. Herschel/PACS observations at 70 and 160µm probe the disk
properties (mass, dust sizes, structure) and the evolutionary state of
a large number of young stars. Far-IR data also trace the remnant
cloud material and small-scale cloud structure. We detect 95
protoplanetary disks at 70µm, 41 at 160µm, and obtain upper
limits for more than 130 objects. The detection fraction at 70µm
depends on the spectral type (88% for K4 or earlier stars, 17% for M3
or later stars) and on the disk type (∼50% for full and
pre-transitional disks, ∼35% for transitional disks, no
low-excess/depleted disks detected). Non-accreting disks are not
detected, suggesting significantly lower masses. Accreting transition
and pre-transition disks have systematically higher 70µm excesses
than full disks, suggestive of more massive, flared and/or thicker
disks. Herschel data also reveal several mini-clusters in Tr37, which
are small, compact structures containing a few young stars surrounded
by nebulosity. Far-IR data are an excellent probe of the evolution of
disks that are too faint for sub-millimetre observations. We find a
strong link between far-IR emission and accretion, and between the
inner and outer disk structure. Herschel confirms the dichotomy
between accreting and non-accreting transition disks. Accretion is a
powerful measure of global disk evolution: substantial mass depletion
and global evolution need to occur to shut down accretion in a
protoplanetary disk, even if the disk has inner holes. Disks likely
follow different evolutionary paths: low disk masses do not imply
opening inner holes, and having inner holes does not require low disk
masses. The mini-clusters reveal multi-episodic star formation in
Tr37. The long survival of mini-clusters suggest that they formed from
the fragmentation of the same core. Their various morphologies favour
different formation/triggering mechanisms acting within the same
cluster. The beads-on-a-string structure in one mini-cluster is
consistent with gravitational fragmentation or gravitational focusing,
acting on very small scales (solar-mass stars in ∼0.5pc filaments).
Multi-episodic star formation could also produce evolutionary
variations between disks in the same region. Finally, Herschel also
unveils what could be the first heavy mass loss episode of the O6.5
star HD 206267 in Tr 37.
Description:
The Cep OB2 clusters, Tr 37 (centered at 21:38:09, +57:26:48,
J2000) and NGC 7160 (centered at 21:53:40, 62:36:10, J2000), were
observed with the ESA Herschel Space Observatory using the
Photodetector Array Camera and Spectrometer (PACS), as part of the
open time (OT) program "Disk dispersal in Cep OB2" (PI A.
Sicilia-Aguilar). We obtained a total of 23h observing time in
parallel mode at 70 and 160um.
Observations took place between November 2012 and January 2013.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 161 77 PACS photometry of previously known CepOB2
members identified by optical spectroscopy
tablea2.dat 99 20 PACS photometry of CepOB2 members identified by
Spitzer/X-ray/Hα photometry
tablea3.dat 179 119 PACS upper limits for previously known CepOB2
members with disks
tablea4.dat 95 35 PACS upper limits of CepOB2 members identified
by Spitzer/X-ray/Hα photometry
--------------------------------------------------------------------------------
See also:
J/AJ/130/188 : Young stars in Tr 37 and NGC 7160 (Sicilia-Aguilar+, 2005)
J/ApJ/702/1507 : Mid-IR photometry in IC 1396A (Morales-Calderon+, 2009)
J/MNRAS/415/103 : IPHAS T Tauri candidates in IC 1396 (Barentsen+, 2011)
J/MNRAS/426/2917 : X-rays sources in Trumpler 37 (Getman+, 2012)
J/A+A/559/A29 : BR 1202-0725 system in [CII] line (Carniani+, 2013)
J/A+A/551/A34 : SED information for CrA members (Sicilia-Aguilar+, 2013)
Byte-by-byte Description of file: tablea1.dat tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Name (G1)
21- 28 A8 --- SpType Spectral type (1)
30- 34 F5.3 mag AV Absorption in V band (1)
35 A1 --- ---
36- 40 F5.3 mag AV2 ? Second value of absorption in V band (1)
42- 47 F6.1 0.1nm EWHa ?=- Hα equivalent width (1)
48 A1 --- --- [/]
49- 51 I3 0.1nm EWHa2 ?=- Second Hα equivalent width
value (1)
52 A1 --- --- [/]
53- 55 I3 0.1nm EWHa3 ?=- Third Hα equivalent width
value (1)
57- 72 A16 --- 2MASS 2MASS designation (HHMMSSss+DDMMSSs)
74- 75 A2 --- l_F70 [≤ ] Limit (<) or marginal detection
(≤) flag on F70um (2)
76- 80 F5.3 Jy F70 ? Herschel/PACS flux density at 70um
82- 86 F5.3 Jy e_F70 ? rms uncertainty on F70
87 A1 --- u_F70 Uncertainty flag on F70
88- 90 A3 --- n_F70 Note on F70 (3)
92- 93 A2 --- l_F100 [≤ ] Limit (<) or marginal detection
(≤) flag on F100um (2)
94- 99 F6.4 Jy F100 ?=- Herschel/PACS flux density at 100um
100 A1 --- --- [/]
101-105 F5.3 Jy F100b ? Second value of flux density at 100um
107-111 F5.3 Jy e_F100 ? rms uncertainty on F100
112 A1 --- u_F100 Uncertainty flag on F100
113 A1 --- n_F100 [1/2] Note on F100um (3)
116-124 A9 --- Disk Disk type (G2)
125 A1 --- l_Acc Limit flag on Acc
126-130 F5.2 10-8Msun/yr Acc ? Accretion from photometry (4)
131 A1 --- --- [+]
132-135 F4.2 10-8Msun/yr E_Acc ? Error on Accretion (upper value)
136 A1 --- --- [-]
137-140 F4.2 10-8Msun/yr e_Acc ? Error on Accretion (lower value)
141-146 A6 --- n_Acc Accretion from optical spectroscopy (4)
149-178 A30 --- Com Comments (5)
179 A1 --- n_Com [*] Uncertain photometry (6)
--------------------------------------------------------------------------------
Note (1): Spectral types, extinction and Hα EW from Sicilia-Aguilar et al.
(2005AJ....130..188S 2005AJ....130..188S, Cat. J/AJ/130/188, 2013A&A...551A..34S 2013A&A...551A..34S,
Cat. J/A+A/551/A34, 2013A&A...559A..29C 2013A&A...559A..29C, Cat. J/A+A/559/A29). Information on
massive stars from Contreras et al. (2002AJ....124.1585C 2002AJ....124.1585C).
Note (2): Marginal detections (detected objects for which visual inspection
suggests there could be some problems) are marked as ≤ to distinguish from
non-detections.
Note (3): Notes as follows:
1 = The 160um point may be a background object
2 = There is a clear point-source detection, but given the small offset with
respect to the optical counterparts and the lack of Spitzer excess,
it may correspond to a background source
out = out
Note (4): The "Acc" column lists the value of the accretion derived from
U band photometry (Sicilia-Aguilar et al. 2005AJ....130..188S 2005AJ....130..188S,
Cat. J/AJ/130/188, 2010ApJ...710..597S 2010ApJ...710..597S, Cat. J/ApJ/710/597), and the
"n_Acc" ones indicates the presence (yes [Y], no [N], uncertain [U], not
measured [-], added [:] indicates a border-line case) of accretion as revealed
by optical spectroscopy (Sicilia-Aguilar et al., 2005AJ....130..188S 2005AJ....130..188S,
Cat. J/AJ/130/188, 2006AJ....132.2135S 2006AJ....132.2135S, Cat. J/AJ/132/2135). Only
high-resolution spectroscopy produces conclusive values in case of border-line
objects with weak Hα EW, which are otherwise labelled as "uncertain".
The detectability limit for objects considered as non-accreting is
10-11M☉/yr. Note that all objects with accretion upper limits are
confirmed to be accreting (via Hα spectroscopy).
Note (5): The comments include "n" (nebular contamination in the region,
although unless stated, the object is detected), "e" (near edge, the data
are fine but the S/N is poorer than at the map centre).
In tablea3.dat, many of the objects in the IC 1396A globule appear without
photometric data in the red since the upper limits that can be constrained
are of a few Jy and thus not informative.
Note (6): *: The object is clearly seen in the blue although due to the
surrounding nebular emission, the photometry is very uncertain.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat tablea4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- 2MASS 2MASS designation (JHHMMSSss+DDMMss)
18 A1 --- n_2MASS [a] Note (2)
20- 33 A14 --- SpType Spectral type (1)
35- 36 A2 --- l_F70 [≤ ] Marginal detection flag on F70
37- 41 F5.3 Jy F70 Herschel/PACS flux density at 70um
43- 47 F5.3 Jy e_F70 ? rms uncertainty on F70
48 A1 --- u_F70 Uncertainty flag on F70
49 A1 --- n_F70 [1] Note on F70um (2)
51 A1 --- l_F100 Limit flag on F100
52- 56 F5.3 Jy F100 ?=- Herschel/PACS flux density at 100um
58- 62 F5.3 Jy e_F100 ? rms uncertainty on F100
63 A1 --- u_F100 Uncertainty flag on F100
65- 68 A4 --- Ref References (3)
70- 76 A7 --- Disk Disk type (G2)
78- 99 A22 --- Com Comments (4)
--------------------------------------------------------------------------------
Note (1): All spectral types (except the one from HD 206267) are derived from
SED fitting and thus subject to large uncertainties, assuming the extinction
will be within the usual cluster values AV=1-3mag.
Note (2): Notes as follows:
1 = given the presence of cloud and the absence of mid-IR excess, the PACS
excess is most likely nebular and the objects do not have evidence of
disks.
a = A nearby source 21371737+5729207 has bright excess, original coordinates
correspond to a point between both objects.
Note (3): References as follows:
M09 = Mercer et al. 2009AJ....138....7M 2009AJ....138....7M)
MC09 = Morales-Calderon et al. 2009ApJ...702.1507M 2009ApJ...702.1507M, Cat. J/ApJ/702/1507)
B11 = Barentsen et al. 2011MNRAS.415..103B 2011MNRAS.415..103B, Cat. J/MNRAS/415/103)
G12 = Getman et al. 2012MNRAS.426.2917G 2012MNRAS.426.2917G, Cat. J/MNRAS/426/2917)
Note (4): The comments include "m" (marginal detection, marked as ≤ to
distinguish from non-detection), "n" (nebular contamination in the region
resulting in very high upper limits), "e" (near edge, the data are fine but
the S/N is poorer than at the map centre).
--------------------------------------------------------------------------------
Global notes:
Note (G1): Nomenclature note:
* NN-NNNN are [SHB2004] NGC 7160 NN-NNNN in Simbad,
* MVA-NNNN are Cl* Trumpler 37 MVA NNNN,
* KUN-NNN are Cl* Trumpler 37 KUN NNN,
* DG-NNN are Cl* NGC 7160 DG NNN.
Note (G2): Keys to disk types:
N = no disk
F = full disk
TD = transition disk
TD8 = transition disk with an excess at 8um only, usually too faint
to be detected at 24um
PTD = pre-transitional disk
D = depleted disk
Db = debris disk
U = uncertain, usually due to photometric errors/contamination
- = not enough information
--------------------------------------------------------------------------------
History:
* 09-Feb-2015: from electronic version of the journal
* 22-Mar-2015: in table A3(#57), the 2MASS name for 213839749+572753080,
originally 21383975+5727530, was corrected into 21383956+5729164
(End) Patricia Vannier [CDS] 09-Feb-2015