J/AJ/141/134 New classification of young planetary nebulae (Sahai+, 2011)
Young planetary nebulae: Hubble Space Telescope imaging and a new morphological
classification system.
Sahai R., Morris M.R., Villar G.G.
<Astron. J., 141, 134 (2011)>
=2011AJ....141..134S 2011AJ....141..134S
ADC_Keywords: Planetary nebulae ; Morphology
Keywords: circumstellar matter - ISM: jets and outflows -
planetary nebulae: general - stars: AGB and post-AGB -
stars: mass-loss - techniques: image processing
Abstract:
Using Hubble Space Telescope images of 119 young planetary nebulae
(PNs), most of which have not previously been published, we have
devised a comprehensive morphological classification system for these
objects. This system generalizes a recently devised system for
pre-planetary nebulae, which are the immediate progenitors of PNs.
Unlike previous classification studies, we have focused primarily on
young PNs rather than all PNs, because the former best show the
influences or symmetries imposed on them by the dominant physical
processes operating at the first and primary stage of the shaping
process. Older PNs develop instabilities, interact with the ambient
interstellar medium, and are subject to the passage of photoionization
fronts, all of which obscure the underlying symmetries and geometries
imposed early on. Our classification system is designed to suffer
minimal prejudice regarding the underlying physical causes of the
different shapes and structures seen in our PN sample, however, in
many cases, physical causes are readily suggested by the geometry,
along with the kinematics that have been measured in some systems.
Secondary characteristics in our system, such as ansae, indicate the
impact of a jet upon a slower-moving, prior wind; a waist is the
signature of a strong equatorial concentration of matter, whether it
be outflowing or in a bound Keplerian disk, and point symmetry
indicates a secular trend, presumably precession, in the orientation
of the central driver of a rapid, collimated outflow.
Description:
The objects included in this work mostly come from several surveys
with HST/WFPC2, most of them fitting the selection criterion of ST98,
namely, that the [OIII] λ5007/Hα flux ratio, Rexc, be
less than about unity used to select young PNs.
We apply our new morphological classification scheme to a new sample
of PNe recently imaged as part of the SNAPshot survey of PNs with the
WFC3/HST instrument (GO 11657, PI: Stanghellini). See Table 5.
All images discussed in this paper which were taken with WFPC2 were
downloaded from the HST archive of pipeline-calibrated images
maintained at the Canadian Astronomy Data Centre (CADC). The images
taken with Advanced Camera for Surveys (ACS) or WFC3 are
pipeline-calibrated images downloaded from the StScI/MAST archive.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 132 38 *Morphological classification codes
table3.dat 119 119 Properties of young planetary nebulae
table5.dat 69 47 Morphological classification for PNs
from HST program GO 11657
notes.dat 80 141 Notes
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Note on table2.dat: We have calculated the fractions of objects in different
primary classes (Table 4), both using the sub-sample of PNs in which
Rexc≤1 (96 objects) and the full sample (119 objects): the
differences are not statistically significant. Here is Table 4:
-----------------------------------------------------
Classification Number Fraction Number Fraction
Rexc≤1 All objects
-----------------------------------------------------
B 27 0.28 33 0.28
M 18 0.19 23 0.20
E 32 0.34 37 0.31
I 6 0.063 8 0.068
R 4 0.042 4 0.034
L 7 0.074 10 0.085
S 2 0.021 4 0.034
-----------------------------------------------------
Point Symmetry
-----------------------------------------------------
B, ps^c 12 0.44 14 0.45
M, ps^d 15 0.83 19 0.83
E, ps^e 13 0.41 15 0.42
ps^f 42 0.44 53 0.45
-----------------------------------------------------
Notes.
c = Number of point-symmetric objects in class B, and as a fraction
of the total in class B.
d = Number of point-symmetric objects in class M, and as a fraction
of the total in class M.
e = Number of point-symmetric objects in class E, and as a fraction
of the total in class E.
f = Total number and fraction of point-symmetric objects, including
objects of the S primary class, which is point symmetric by definition.
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
V/84 : Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker+, 1992)
J/A+AS/76/317 : Possible new PNe in IRAS PSC (Preite-Martinez, 1988)
J/ApJS/112/487 : Planetary nebulae classification (Soker 1997)
J/A+AS/132/13 : Planetary nebulae radial velocities (Durand+ 1998)
J/A+A/458/173 : Optical spectroscopy of 253 IRAS sources (Suarez+, 2006)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Char [PS] Primary or Secondary characteristics
3- 4 A2 --- Type Characteristics used for the class (1)
6- 12 A7 --- Class Classification code
18-132 A115 --- Text Explanation of the classification code
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Note (1): Type of classification as follows:
NS = Nebular Shape
L = Lobes
CR = Central Region
CS = Central Star
O = Other Nebular Characteristics
PS = Point Symmetry
H = Halo
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Sam Sample (≤1 or >1) defined from line ratio
Rexc=[OIII]λ5007/Hα ratio
5- 12 A8 --- PK Object name in PK (Perek-Kohoutek) format
14- 23 A10 --- PNG Object name in PNG format
25- 26 I2 --- n_PNG [12/54]? Note on object, in notes.dat file
28- 31 A4 --- P Primary classification and secondary descriptor
related to whether the lobes (or the shell in
the case of an E primary classification) are
open or closed (1)
33- 42 A10 --- CR Secondary descriptors for the central region (1)
44- 54 A11 --- PS Secondary descriptors describing the symmetry (1)
55- 68 A14 --- OS All remaining secondary descriptors (1)
70 A1 --- l_Rexc Limit flag on Rexc
71- 74 F4.2 --- Rexc [0/4.5] Line flux ratio
Rexc=[OIII]λ5007/Hα
78- 82 F5.2 arcsec Size [0.6/61.3] Angular size of the object
84- 87 F4.1 km/s V1 [5.5/41]? Expansion velocity measured from the
[NII]λ6583 line ratio as listed in the
Acker+ (1992, V/84)
89 A1 --- l_V2 Limit flag on V2
90- 93 F4.1 km/s V2 [4/70]? Expansion velocity measured from the
[OIII] line as listed in the Acker+ (1992, V/84)
96-100 F5.2 kpc Dist [0.6/24.8]? Distance to the object
102-106 I5 yr Age [170/13676]? Derived expansion age
108-113 F6.3 arcsec Xbox [2.2/69.7]? Size of the panel (along the
horizontal axis) in the figure of the object
(∼size of nebula)
115-119 A5 --- Fig The number of the figure showing the object
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Note (1): Morphological classification (explained in table2.dat),
divided into four parts:
* (1) the primary classification and the secondary descriptor related
to whether the lobes (or the shell in the case of an E primary
classification) are open or closed
* (2) the secondary descriptors for the central region,
* (3) the secondary descriptors describing point symmetry
* (4) all remaining secondary descriptors.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Sam Sample with Rexc=[OIII]λ5007/Hα
ratio ≤1 or >1
11- 20 A10 --- PNG Object name in PNG format
22 A1 --- f_PNG Flag on PNG (1)
24- 26 A3 --- P Primary classification
28- 35 A8 --- CR Secondary descriptors for the central region
37- 46 A10 --- PS Secondary descriptors describing the symmetry
48- 55 A8 --- OS All remaining secondary descriptors
57 A1 --- l_Rexc Limit flag on Rexc
59- 63 F5.3 --- Rexc [0/4] Line flux ratio
Rexc=[OIII]λ5007/Hα
65- 69 F5.2 --- Fig [19/20.9]? The number of the figure
showing the object
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Note (1): Flag as follows:
a = PNG344.2+04.7: although we assign B as the primary class, this object
may be intrinsically multipolar (M), with the inner bright lobe pair
component having its axis projected along the axis of the larger,
faint primary lobe pair.
b = PNG048.5+04.2: the axis of the bipolar lobes, which are apparently
inclined at a relatively small inclination to the line of sight, is
oriented at p.a. ∼50°. An elongated diffuse nebulous structure can
be seen with its major axis at p.a.∼140°, but gives its rather
limited radial extent, we tentatively classify it as a halo, i.e., as
h(e,d)?.
c = PNG053.3+24.0: the "t" descriptor refers to the bright structure
oriented with its long axis along p.a. ~-20°; however, it is
possible that this structure is actually a lobe structure, similar to
that seen in the multipolar PPN, IRAS19475+3119
(Sahai+ 2007ApJ...658..410S 2007ApJ...658..410S), suggesting the alternative
classification M, c, *, ib, ps(m,ib), h(e).
d = PNG068.7+01.9: we use "a?" for the qualifier in the halo
descriptor, since only a single, partial arc-like feature is seen.
e = PNG285.4+01.5: we assign the feature at p.a.~-50° the minor lobe
descriptor ml, but it is possible that this is a planar structure
whose radial density distribution has a sharp outer edge, in which
case it would be better described by the w(b) descriptor used for PPNs
(SMSC07). We use "a?" for the qualifier in the halo descriptor, since
only a single, partial arc-like feature is seen.
f = PNG309.5-02.9: we assign this a primary class L; the collimated
lobes are seen weakly at p.a. ∼70°. The bright structure surrounding
the central star is an inner bubble, and the torus is the ring-like
structure which is brightest on the right side of the central star in
the image.
g = PNG343.4+11.9: a well-defined nebular shell is not seen in this
object; we assume that the inner bright region oriented at p.a.~-15°
represents the primary nebula, and the surrounding diffuse structure
is the halo.
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Note Note number
4- 80 A77 --- Text Text of the note
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 04-Aug-2012