Microwave Observations of Edge-on Protoplanetary Disks: Program Overview and First Results

Abstract

We are undertaking a multi-frequency Expanded Very Large Array (EVLA) survey
of edge-on protoplanetary disks to probe the growth of solids in each disk,
sedimentation of such material into the disk midplane, and the connection of
these phenomena to the planet formation process. The projection of edge-on disk
systems along our line of sight enables a study of the vertical stratification
of large grains with fewer model dependencies than would be required for disks
that are more face-on. Robust studies of the spatial distribution of grains up
to ~1 cm in size are possible with the wavelength range and sensitivity of the
EVLA. In this contribution we describe target selection and observational
strategies. First results concerning the Class 0 source IRAS04368+2557 (L1527
IRS) are presented, including a study of this source's 8.46 GHz continuum
variability over short and long time baselines and an indication that its
protoplanetary disk may have a dearth of pebble-sized grains.

Full text

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arXiv:1106.4519v2 [astro-ph.SR] 24 Jun 2011
Microwave Observations of Edge-on Protoplanetary Disks:
Program Overview and First Results
Carl Melis1,10, G. Duchˆ ene2,3, Laura Chomiuk4,5, Patrick Palmer6, M. D. Perrin7, S. T.
Maddison8, F. M´ enard3, K. Stapelfeldt9, C. Pinte3, G. Duvert3
cmelis@ucsd.edu
ABSTRACT
We are undertaking a multi-frequency Expanded Very Large Array (EVLA)
survey of edge-on protoplanetary disks to probe the growth of solids in each disk,
sedimentation of such material into the disk midplane, and the connection of
these phenomena to the planet formation process. The projection of edge-on
disk systems along our line of sight enables a study of the vertical stratification
of large grains with fewer model dependencies than would be required for disks
that are more face-on. Robust studies of the spatial distribution of grains up to
≈1cm in size are possible with the wavelength range and sensitivity of the EVLA.
In this contribution we describe target selection and observational strategies.
First results concerning the Class 0 source IRAS04368+2557 (L1527IRS) are
presented, including a study of this source’s 8.46GHz continuum variability over
1Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093-0424, USA
2Astronomy Department, 601 Campbell Hall, University of California, Berkeley, CA 94720-3411, USA
3UJF-Grenoble 1/ CNRS-INSU, Institut de Plan´ etologie et d’Astrophysique de Grenoble (IPAG) UMR
5274, BP 53, 38041 Grenoble Cedex 9, France
4Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-66, Cambridge, MA 02138, USA
5A Jansky Fellow of the National Radio Astronomy Observatory
6Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL
60637, USA
7Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21231, USA
8Centre for Astrophysics & Supercomputing, Swinburne University, PO Box 218, Hawthorn, VIC 3122,
Australia
9Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-900, 4800 Oak Grove Drive,
Pasadena, CA 91109, USA
10Joint NSF AAPF Fellow and CASS Postdoctoral Fellow

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short and long time baselines and an indication that its protoplanetary disk may
have a dearth of pebble-sized grains.
Subject headings: accretion, accretion disks — circumstellar matter — planets
and satellites: formation — protoplanetary disks — stars: individual(IRAS04368+2557)
— stars: variables: T Tauri, Herbig Ae/Be
1. Introduction
Both major contending theories of planet formation, core accretion and gravitational
instability, require collection of solid material into a dense mid-plane layer within circum-
stellar disks (e.g., Pollack et al. 1996; Boss 1997; Schr¨ apler & Henning 2004, and references
therein). To understand this first stage in the generation of planetary embryos we must
determine the necessary conditions for grain sedimentation and if the relevant physical pro-
cesses act uniformly with particle size. Numerical simulations incorporating gas drag and
stellar gravity predict that larger grains are expected to settle into the disk mid-plane more
efficiently than smaller grains (e.g., Barri` ere-Fouchet et al. 2005; Laibe et al. 2008). How-
ever, these simulations predict extremely short timescales for the growth and migration of
dust particles that are inconsistent with observations, suggesting that some additional disk
physics needs to be included (see Brauer et al. 2007). Observational results, and modeling
thereof (e.g., Duchˆ ene et al. 2003; Pinte et al. 2007), have begun to lay the foundation for
grain sedimentation and its relation to grain growth, providing evidence in support of larger
grains being more concentrated towards the disk mid-plane. Although these works hint that
grain growth, radial migration, and sedimentation are intimately connected, observations
that resolve the spatial distribution of large grains are necessary to complete this picture.
Study of the largest dust grains and their spatial distribution requires observations at
long wavelengths (commensurate with grain size; e.g., Natta et al. 2004; Wilner et al. 2005;
Rodmann et al. 2006; Lommen et al. 2009). Unambiguous grain vertical distribution in-
formation can only come from protoplanetary disks which are edge-on to our line of sight
(Section 2). Edge-on protoplanetary disk systems imaged in scattered light typically sub-
tend ∼0.3-3′′in the vertical direction (see Table 1 references). To identify vertical grain
stratification, thermal emission from disk atmosphere grains must be separated from that
of grains settled to the disk mid-plane with high angular resolution observations. Hence, to
study the vertical distribution of large grains, one must map edge-on disk systems with a
long-baseline radio interferometer such as the NRAO1Expanded Very Large Array (EVLA;
1The National Radio Astronomy Observatory is a facility of the National Science Foundation operated

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Perley et al. 2011).
In this contribution we present an EVLA survey of edge-on protoplanetary disk sys-
tems. Target selection and observations are discussed, and first results on the source
IRAS04368+2557 are reported.
2. Sample Definition
Edge-on disks are selected because of their favorable geometry: each beam of an edge-on
disk map samples a single disk altitude. From spectral index maps of edge-on disk systems
we will measure the maximum grain size per synthesized beam and hence the vertical distri-
bution of grains as a function of grain size. Some assumptions regarding disk axisymmetry
may be necessary to delineate optical depth effects from true grain size variation, especially
near the disk mid-plane (see also discussion in Section 4.3).
We arbitrarily restrict our sample to disks with inclination angle ?75◦(where 0◦is face-
on to our line of sight) to limit confusion between radial and altitude flux variations. All
sources in our sample have been selected based on the existence of scattered light images that
allow a determination of the disk inclination to a few degrees. Ultimately, such a sample will
enable more powerful global panchromatic analyses (e.g., Pinte et al. 2008; Duchˆ ene et al.
2010).
Disk systems observed in the first EVLA observing cycle are listed in Table 1.
3. Observational Strategy
Preliminary observations aim to identify microwave-bright disks for future mapping and
to characterize the overall degree of grain growth for each disk system based on measure-
ment of their long-wavelength opacity index β (where κν ∝ νβ). The value of β provides
information on the size of grains relative to the observing wavelength, where β?1 indicates
grains comparable to or larger than the observing wavelength (e.g., Beckwith et al. 1990;
Mannings & Emerson 1994; Rodmann et al. 2006; Lommen et al. 2009; Ricci et al. 2010;
Section 4.3 discusses how disk optical depth affects the determination of β). These goals
require total power measurements (i.e., unresolved disk measurements) which are best done
in compact array configurations.
under cooperative agreement by Associated Universities, Inc.

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Disk flux measurements are made at 7 and 13mm. Robust measurement of the opac-
ity index β requires removing emission from processes other than dust thermal emission.
Young stellar objects are known to emit in the microwave due to free-free emission from
ionized jets and disk-winds and gyrosynchrotron emission from coronal processes (see e.g.,
Osten & Wolk 2009, and references therein). Previous works have shown that free-free and
gyrosynchrotron emission (hereafter non-disk emission) can contaminate the 7-13mm wave-
length region at a level that is anywhere from 0-100% of the detected flux (e.g., Natta et al.
2004; Rodmann et al. 2006). It is assumed that measurements longward of 20mm are prob-
ing only non-disk emission (this is not always the case; see Wilner et al. 2005). We perform
observations at both 35 and 60mm so that there are two data points with which to determine
the spectral slope of non-disk emission components.
Non-disk emission is known to be variable (e.g., Osten & Wolk 2009). Proper removal
of this variable emission requires observations of the non-disk component that are as close
in time as possible to observations of the disk component. To obtain quasi-simultaneous
observations across all bands, we intertwined scans at 7, 13, 35, and 60mm within a con-
tinuous observing block (which can span 3-5 hours; see Table 2). Although these disk and
non-disk measurements are not perfectly simultaneous, the assumption is that averaging 35
and 60mm scans taken over the entire observing block will yield an accurate measurement
of the non-disk emission component during 7 and 13mm scans. We test this strategy in
Section 4.2.
4.Case Study: IRAS04368+2557
Of the 11 sources observed in the first EVLA cycle, 9 were detected (Table 1). In this
section observations of IRAS04368+2557 (L1527IRS) are presented as a case study of the
methodologies outlined above.
IRAS04368+2557 is an embedded class 0 object in the L1527 dark cloud in Taurus
(White & Hillenbrand 2004). Although optically faint (e.g., White & Hillenbrand 2004),
IRAS04368+2557 is bright in the sub-millimeter (Chandler & Richer 2000; Andrews & Williams
2005), millimeter (Ohashi et al. 1997; Motte & Andr´ e 2001), and microwave (Rodr´ ıguez & Reipurth
1998; Loinard et al. 2002). Millimeter and sub-millimeter results to date show that IRAS04368+2557
is composed of a substantial envelope that is infalling onto the central source (Ohashi et al.
1997; Chandler & Richer 2000; Motte & Andr´ e 2001; Andrews & Williams 2005).
imaging detects jet emission emanating from the central protostar (Rodr´ ıguez & Reipurth
1998; Reipurth et al. 2004) and provides evidence of a ∼24AU binary companion (Loinard et al.
2002). The disk surrounding the central source is probed most recently by Tobin et al.
VLA

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(2010) who present 3.78µm imaging that resolves the inner envelope and disk structure
of IRAS04368+2557. The only unambiguous detection of disk thermal emission comes
from Loinard et al. (2002) who resolve the disk at 7mm. Our observations provide the
first nearly simultaneous, multiband, compact configuration radio frequency observations of
IRAS04368+2557.
4.1. Observations
IRAS04368+2557 was observed with all 27 EVLA antennas. Some details of the obser-
vations are given in Table 2. The WIDAR correlator was set up with two 128MHz sub-bands
centered on the frequencies listed in Table 2. Each sub-band had 4 polarization products
(RR, LL, RL, LR) and sixty-four 2000kHz channels. Observations at 7 and 13mm were per-
formed in “fast-switching” mode; target source scans were interleaved with frequent visits to
a nearby calibration source to freeze out rapid atmospheric phase fluctuations. Cycle times
of 2 and 4 minutes were used for 7 and 13mm, respectively. The primary calibration source
3C286 was used to measure the complex bandpass and to set the absolute flux scale.
To probe the stability of the non-disk emission component over long and short time
baselines we retrieved VLA archival 35mm observations of IRAS04368+2557 (see Table
2). To maintain homogeneity in this data set we only use observations performed with all
VLA antennas. VLA observations were made in both circular polarizations with an effective
bandwidth of 92MHz centered at a frequency of 8.46GHz. Data from AR0350 and AR0465
are presented in Rodr´ ıguez & Reipurth (1998) and Reipurth et al. (2004), respectively. All
other data are unpublished to the best of our knowledge. While our reductions agree well
with those of Rodr´ ıguez & Reipurth (1998), we find a significantly lower flux density for
IRAS04368+2557 than do Reipurth et al. (2004).
measurement is consistent with what is displayed in Figure 2 of Reipurth et al. (2004), but
that this and our measurement are both inconsistent with what is listed in their Table 2.
Further investigation shows that our
All data are reduced using the Astronomical Image Processing Software (AIPS; Greisen
2003). VLA data are edited and calibrated following standard VLA data reduction proce-
dures. EVLA data are edited and calibrated in a similar manner, except for the addition of
first pass fringe fitting to set the interferometer delays (performed on the primary calibrator,
3C286) and bandpass calibration. Standard high-frequency reduction techniques are em-
ployed for 7mm data. IRAS04368+2557 is detected at all observed frequencies with ?10σ
significance. We assume absolute flux density scale systematic uncertainties of 15% and 5%
for 7 and 13mm, respectively; these are included in the Table 2 uncertainties. Absolute flux
densities for 35 and 60mm are assumed to be limited by the rms noise level in CLEANed

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maps. Figure 1 shows contour maps from the EVLA data; IRAS04368+2557 is not resolved
in any of the EVLA images.
4.2. Centimetric Variability
Figure 2 presents 35mm measurements of IRAS04368+2557 from each epoch listed
in Table 2. Inter-epoch measurements are made by imaging all data obtained in the time
interval listed for that epoch. Intra-epoch measurements are made by imaging the smallest
time interval that yields an ≈10σ detection of IRAS04368+2557.
Except for the 2002 data, no significant (>3σ) inter-epoch variability is detected. The
2002 observations were done with the most extended array configuration and emission struc-
tures could have been resolved out by the widely separated baselines resulting in lower than
average flux densities. Intra-epoch measurements reveal two transient events. The first is a
mini-flare observed near the end of the 26 minute long UT 1997 Aug 14 scan. The second
is the radio jet detected by Reipurth et al. (2004) which appears only near the end of the
UT 2002 Feb 08 data set. Out of eighteen ≈25 minute long 35mm IRAS04368+2557 se-
quences, one exhibits a flare event and one exhibits a jet event. The occurrence rate of such
events in 25 minute windows is ∼6% if the events are unique and ∼11% if they are the same
phenomenon.
Compared to previous studies of young stellar object centimetric variability (e.g., Forbrich et al.
2006, 2007; Choi et al. 2008; Osten & Wolk 2009), the results presented herein appear to
agree best with the Osten & Wolk (2009) study of short and long term variability in six
young stellar objects. At a wavelength of 60mm they find that 4 out of 6 young stellar
objects show short term variability and that 3 out of 6 objects show long term variability
(the positive variability detections are not necessarily from the same objects in each group).
Hence, their results suggest that young stellar objects appear to be just as likely to have
short term variability as they are to exhibit long term variability. Such conclusions seem
to contradict the results of Forbrich et al. (2006, 2007) and Choi et al. (2008), where it is
found that there are generally lower levels of variability on shorter timescales. However, of
the above mentioned studies, only Osten & Wolk (2009) analyze variability on intra-epoch
(less than day) timescales. It could be the case that even seemingly stable sources have
sporadic variability that can only be probed on the shortest timescales. If the event occur-
rence rate derived above for IRAS04368+2557 is representative of stars in the same class,
then such sources might exhibit short-duration flares in as many as one out of ten 25 minute
observing windows. However, since less than ten sources have been probed on intra-epoch
timescales, it is likely premature to extend their results to other sources. Monitoring similar

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to that presented here and in Osten & Wolk (2009) of new and previously studied young
stellar objects can further address variability timescales and strength in a more statistical
sense.
For weak flare events like those detected here, averaging over the duration of an observ-
ing block sufficiently suppresses the flare effect. Stronger flares can likely be identified by
analyzing all data in a time-series fashion. No strong flares are present in the EVLA data.
4.3. Disk Emission Spectral Index
Figure 3 shows the EVLA flux measurements of IRAS04368+2557 with literature mea-
surements at millimeter and sub-millimeter wavelengths. The 450 and 850µm measurements
(Andrews & Williams 2005) were made with beam sizes of 9 and 15′′, respectively, while the
1.3mm measurement (Motte & Andr´ e 2001) was made with a beam size of 11′′. The 2.7mm
measurement (Ohashi et al. 1997) was made with a synthesized beam size of 6′′× 4.9′′(PA
+163◦).
The non-disk emission component is fit with α35−60mm=0.33±0.17 (where α is the spec-
tral index Fν ∝ να), consistent with non-disk indices assumed by Rodmann et al. (2006).
An extrapolation of the non-disk emission fit is subtracted from 7 and 13mm measure-
ments; uncertainties of each flux measurement and the spectral index are propagated into
the corrected flux uncertainties. We calculate for IRAS04368+2557 α0.45−1mm=1.93±0.25
and α1−7mm=2.87±0.17 using the corrected 7mm flux density. We use different spectral
indices for wavelengths ?1mm and ?1mm since single power-law fits to all sub-millimeter
and millimeter data points are discrepant with the 450µm flux measurement at the ≈5σ
level. The spectral index from 450µm to 1.3mm is consistent with Rayleigh-Jeans emis-
sion suggesting that the disk is opaque at these wavelengths. In the case of the 450µm
to 2.7mm measurements, there is likely contamination from extended envelope structure
detected around IRAS04368+2557 (see below and Ohashi et al. 1997; Chandler & Richer
2000; Motte & Andr´ e 2001; Andrews & Williams 2005). If these measurements are contam-
inated by envelope emission, then the disk-only α1−7mmis smaller (flatter) than the value
quoted above. It is noted that the EVLA 7mm flux measurement is roughly consistent with
the total flux density estimated for the resolved structures detected by Loinard et al. (2002).
This suggests that the disk structure is fairly compact (relative to the envelope structure), in
agreement with scattered light images presented by Tobin et al. (2010). IRAS04368+2557
is resolved at wavelengths shorter than 7mm with beam sizes larger than the EVLA 7mm
synthesized beam implying that those flux measurements include envelope emission. Syn-
thesis of the above suggests that accurate measurement of grain growth from spectral indices

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requires data sets having beam sizes comparable to the disk angular size when contaminating
sources are present.
Extracting an opacity index β from the above measured α1−7mmis complicated not only
by envelope contamination but also by edge-on disk geometry. When calculating β one must
account for optically thick inner disk emission sampled by the flux measurements. Should
no optically thick emission be present, then β is simply α1−7mm−2. In the case that optically
thick emission is present in the measurements, β takes the form of (1 + ∆)(α1−7mm−2)
where ∆ is the ratio of optically thick to optically thin emission (Beckwith et al. 1990). As
discussed above, the disk orbiting IRAS04368+2557 appears to be completely opaque out
to wavelengths as long as ∼1mm. Thus, significant optically thick emission may be present
even at wavelengths near 10mm. Estimates of ∆ are typically made assuming some disk
mass density profile and by measuring the temperature profile from spectral indices and disk
flux levels in the optically thick wavelength regime (Beckwith et al. 1990; Rodmann et al.
2006). However, Equation 10 of Beckwith et al. (1990) shows that mapping spectral indices
and disk flux levels into temperature profiles is confounded when disks are nearly edge-on.
Modeling of edge-on disk spectral energy distributions and resolved images can recover their
true disk temperature profiles. Due to this additional modeling and envelope contamination
uncertainties, we leave derivation of the opacity index for the IRAS04368+2557 disk to
future works.
The 13mm measurement appears to fall short of the ν2.87fit after being corrected for
non-disk emission. This flux deficit suggests a break in the disk emission spectral index
from 7 to 13mm, but is marginally significant. If envelope contamination is present as
discussed above, then its removal would increase the significance of the deficient corrected
13mm measurement. Comparison to other protoplanetary disk systems shows that such
a break would be unusual (e.g., Wilner et al. 2005; Rodmann et al. 2006; Lommen et al.
2009) and suggestive of a cut-off near pebble-sizes in the disk grain size distribution. If these
characteristics of IRAS04368+2557 are confirmed, then there may be a connection between
its potential ∼24AU binary companion (Loinard et al. 2002), its apparent 7mm outer disk
truncation (Loinard et al. 2002), and its possible lack of large disk grains.
5. Conclusions
We are carrying out an Expanded Very Large Array program to map the vertical distri-
bution of large grains in edge-on protoplanetary disks. The ultimate goal of this survey is to
study grain growth and sedimentation as the first stages of planet formation. Our compact
array observational strategy aims to provide accurate disk thermal emission measurements

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in the microwave by sampling non-disk emission in concert with disk measurements. First
EVLA results for IRAS04368+2557 show that the protoplanetary disk around this source
is likely optically thick out to millimeter wavelengths and that it may have a dearth of
“pebble-sized” grains.
We thank the anonymous referee for comments that helped improve this work. C.M.
acknowledges support from the National Science Foundation under award No. AST-1003318.
M.D.P. was supported by NSF Postdoctoral Fellowship No. AST-0702933.
and G.D. acknowledge PNPS of CNRS/INSU, and ANR (contract ANR-07-BLAN-0221) of
France for financial support. C.P. acknowledges funding from the European Commission’s
7thFramework Program (contract PIEF-GA-2008-220891) and from ANR under contract
ANR-2010-JCJC-0504-01.
F.M., C.P.,
Facilities: EVLA (), VLA ()
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DECLINATION (J2000)
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Fig. 1.— EVLA images of IRAS04368+2557. The top row shows 7mm (left) and 13mm
(right) maps while the bottom row shows 35mm (left) and 60mm (right) maps. Half-power
contours of the beam are shown in the bottom left of each plot, beam sizes can be found in
Table 2. Contour levels start at −2 times the map rms noise level (dashed contours) and
increment by 4 times the map rms noise level (0.2 mJy, 0.1 mJy, 30 µJy, and 33 µJy for 7,
13, 35, and 60mm respectively).

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– 13 –
0 1000 2000 3000 4000 5000 6000
Julian Date − 2450000 (Days)
0.5

0.7

0.9
Flux Density (mJy)
0102030405060
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 1996 May 12
0510152025
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 1997 Aug 14
05101520
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 1999 Jan 26
0100200300400500
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 2002 Feb 08
0100200300400
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 2002 Mar 02
0100200300400500
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 2002 Mar 04
051015
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 2003 Jan 04
050100150
Time since block start (minutes)
0.4
0.9
1.4
Flux Density (mJy)
UT 2010 Jul 30
Fig. 2.— X-band (8.46GHz; 35mm) measurements of IRAS04368+2557. The top panel
presents inter-epoch measurements (one measurement for each date listed in Table 2; EVLA
data are in red). The dotted line is the mean flux level of all compact array measurements.
The lower panels show intra-epoch measurements for the date listed in each plot. The
abscissa shows time since the Table 2 UT start time of each epoch. Note the mini-flare
detected on UT 1997 Aug 14.

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– 14 –
110100
Wavelength (mm)
0.1
1.0
10.0
100.0
1000.0
Flux Density (mJy)
ν
1.93
ν
2.87
ν
0.33
Fig. 3.— IRAS04368+2557 long-wavelength spectral energy distribution. Uncertainties are
1σ. Red data points longward of 3mm are EVLA data. See Section 4.3 and Table 2 for
measurement beam sizes. The 450µm to 2.7mm measurement errors include 10-25% absolute
flux scale systematic uncertainties. The dotted line fits the 35 and 60mm measurements
which are assumed to be entirely due to non-disk emission (this fit does not include the
13mm data point). Lower, blue triangle data points are corrected measurements (Section
4.3); the 13mm uncertainty extends to 0. The ν2.87fit does not include the corrected 13mm
measurement. See Section 4.3 for a discussion of the two disk emission spectral indices used.

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Table 1.EVLA D-array Observed Targets
Name RADECSpectral
Type
Disk
Class
Inclination
(◦)
Disk Sizea
(′′)
RefDetected?b
(J2000 Phase Center)
Haro 6−5B
IRAS04302+2247
HV Tau C
IRAS04368+2557
CB 26
PDS 144 Nc
LFAM1d
Oph E MM3
Flying Saucer
Gomez’s Hamburger
HH 200
04 22 01.0
04 33 16.5
04 38 35.5
04 39 53.6
04 59 50.7
15 49 15.4
16 26 21.8
16 27 05.9
16 28 13.2
18 09 13.4
20 57 06.6
+26 57 35
+22 53 20
+26 10 41
+26 03 06
+52 04 44
−26 00 52
−24 22 51
−24 37 08
−24 31 39
−32 10 50
+77 36 56
K5
−
II
I
II
0
I-II
II
I
II
II
II
II
75
87
84
85
85
83
85
87
86
84
87
4
2
1,2,3
1,3,4
5,6,7
1,8
9
10,11
12,13,14
12,15
12,16
17,18,19
20,21
Y
Y
Y
Y
Y
Y
Y
Y
N
Y
N
M0
−
0.7
1
2.8
0.8
1
1
4.3
12
1.5
−
A2
−
−
−
A0
−
References. — (1) White & Hillenbrand (2004), (2) Krist et al. (1998), (3) Stark et al. (2006), (4) Wolf et al.
(2003), (5) Appenzeller et al. (2005), (6) Stapelfeldt et al. (2003), (7) Duchˆ ene et al. (2010), (8) Tobin et al.
(2010), (9) Sauter et al. (2009), (10) Vieira et al. (2003), (11) Perrin et al. (2006), (12) van Kempen et al. (2009),
(13) Bontemps et al. (2001), (14) Duchˆ ene et al. (2007), (15) Brandner et al. (2000), (16) Grosso et al. (2003),
(17) Ruiz et al. (1987), (18) Bujarrabal et al. (2008), (19) Bujarrabal et al. (2009), (20) Bally et al. (1995), (21)
Devine et al. (2009).
aDisk angular diameter from optical scattered light or millimeter imaging. In its most extended array configu-