Subaru/HiCIAO $HK_{\rm s}$ imaging of LkH$\alpha$ 330 - disk's color discussion and simultaneous detection of gap and spiral-like structures

Abstract

We present $H$- and $K_{\rm s}$-bands observations of the LkH$\alpha$ 330 disk with a simultaneous detection of a large gap and spiral-like structures. The morphology of the outer disk ($r\sim$$0\farcs3$) at PA=0--45$^\circ$ and PA=180--290$^\circ$ is affected by a density wave-induced spiral despite the possibility of "cavity-like" structures. We have also investigated the azimuthal profiles at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like structures and semi-major axis. Azimuthal analysis shows that the disk has an asymmetric dust distribution. The radial profiles in the major-axis direction (PA=$83^\circ$ and $263^\circ$) suggest that the outer region ($r\geq0\farcs25$) may be influenced by shadows of the inner region of the disk. The spiral-like directions (PA=10$^\circ$ and 230$^\circ$) show different radial profiles, which suggests that the surfaces of the spiral-like structures are highly flared and/or have different dust properties. Finally, a color-map of the disk shows a lack of an outer eastern region in the $H$-band disk, which indicates the presence of a clump-like object in the innermost region ($<1$ au), which occasionally casts a directional shadow onto the disk.

Full text

arXiv:1804.05934v2 [astro-ph.EP] 8 Jun 2018
Draft version June 12, 2018
Preprint typeset using L
A
T
E
X style emulateap j v. 01/23/15
SUBARU/HICIAO HKSIMAGING OF LKHα330 - MULTI-BAND DETECTION OF THE GAP AND
SPIRAL-LIKE STRUCTURES
Taichi Uyama1, Jun Hashimoto2, Takayuki Muto3, Eiji Akiyama4, Ruobing Dong5, Jerome de Leon1, Itsuki
Sakon1, Tomoyuki Kudo6, Nobuhiko Kusakabe2, Masayuki Kuzuhara2, Mickael Bonnefoy7, Lyu Abe8,
Wolfgang Brandner9, Timothy D. Brandt10,11, Joseph C. Carson12,9, Thayne Currie6, Sebastian Egner6,
Markus Feldt9, Jeffrey Fung13, Miwa Goto14, Carol A. Grady15,16,17, Olivier Guyon2,6,5, Yutaka Hayano6,
Masahiko Hayashi18, Saeko S. Hayashi6, Thomas Henning9, Klaus W. Hodapp19, Miki Ishii18 , Masanori Iye18,
Markus Janson21, Ryo Kandori18, Gillian R. Knapp21, Jungmi Kwon20, Taro Matsuo22, Satoshi Mayama23,
Michael W. Mcelwain15, Shoken Miyama24, Jun-Ichi Morino18, Amaya Moro-Martin21,25, Tetsuo Nishimura6,
Tae-Soo Pyo6, Eugene Serabyn26, Michael L. Sitko27,28, Takuya Suenaga18,29, Hiroshi Suto2,18, Ryuji Suzuki18,
Yasuhiro H. Takahashi1,18, Michihiro Takami30, Naruhisa Takato6, Hiroshi Terada18, Christian Thalmann31,
Edwin L. Turner21,32, Makoto Watanabe33, John Wisniewski34, Toru Yamada35, Yi Yang29, Hideki Takami18,
Tomonori Usuda18, and Motohide Tamura1,2,18
Draft version June 12, 2018
ABSTRACT
We present H- and Ks-bands observations of the LkHα330 disk with a multi-band detection of
the large gap and spiral-like structures. The morphology of the outer disk (r∼0.
′′3) at PA=0–45◦
and PA=180–290◦are likely density wave-induced spirals and comparison between our observational
results and simulations suggests a planet formation. We have also investigated the azimuthal profiles
at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like
structures and semi-major axis. Azimuthal analysis shows a large variety in wavelength and implies
that the disk has non-axisymmetric dust distributions. The radial profiles in the major-axis direction
(PA=271◦) suggest that the outer region (r≥0.
′′25) may be influenced by shadows of the inner region
of the disk. The spiral-like directions (PA=10◦and 230◦) show different radial profiles, which suggests
that the surfaces of the spiral-like structures are highly flared and/or have different dust properties.
Finally, a color-map of the disk shows a lack of an outer eastern region in the H-band disk, which
may hint the presence of an inner object that casts a directional shadow onto the disk.
1Department of Astronomy, The University of Tokyo, 7-3-1,
Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
2Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo
181-8588, Japan
3Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-
Shinjuku, Shinjuku-ku, Tokyo, 163-8677, Japan
4Chile Observatory, National Astronomical Observatory of
Japan, 2-21-2, Osawa, Mitaka, Tokyo, 181-8588, Japan
5Steward Observatory, University of Arizona, Tucson, AZ
85721, USA
6National Astronomical Observatory of Japan, Subaru Tele-
scope, National Institutes of Natural Sciences, Hilo, HI 96720,
USA
7Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble,
France
8Laboratoire Lagrange (UMR 7293), Universite de Nice-
Sophia Antipolis, CNRS, Observatoire de la Coted’azur, 28 av-
enue Valrose, 06108 Nice Cedex 2, France
9Max Planck Institute for Astronomy, K¨onigstuhl 17, 69117
Heidelberg, Germany
10 Department of Physics, University of California-Santa Bar-
bara, Santa Barbara, CA, USA
11 Astrophysics Department, Institute for Advanced Study,
Princeton, NJ, USA
12 Department of Physics and Astronomy, College of
Charleston, 66 George St., Charleston, SC 29424, USA
13 Department of Astronomy, University of California, Berke-
ley, CA, USA
14 Universit¨ats-Sternwarte M¨unchen, Ludwig-Maximilians-
Universit¨at, Scheinerstr. 1, 81679 M ¨unchen,Germany
15 Exoplanets and Stellar Astrophysics Laboratory, Code 667,
Goddard Space Flight Center, Greenbelt, MD 20771, USA
16 Eureka Scientific, 2452 Delmer, Suite 100, Oakland
CA96002, USA
17 Goddard Center for Astrobiology
18 National Astronomical Observatory of Japan, 2-21-1, Os-
awa, Mitaka, Tokyo, 181-8588, Japan
19 Institute for Astronomy, University of Hawaii, 640 N. Ao-
hoku Place, Hilo, HI 96720, USA
20 Institute of Space and Astronautical Science, JAXA, 3-1-1
Yoshinodai, Sagamihara, Kanagawa Japan
21 Department of Astrophysical Science, Princeton University,
Peyton Hall, Ivy Lane, Princeton, NJ08544, USA
22 Department of Earth and Space Science, Graduate School
of Science, Osaka University, 1-1 Machikaneyamacho, Toyonaka,
Osaka 560-0043, Japan
23 SOKENDAI(The Graduate University for Advanced Stud-
ies), Shonan International Village, Hayama-cho, Miura-gun,
Kanagawa 240-0193, Japan
24 Hiroshima University, 1-3-2, Kagamiyama, Higashihi-
roshima, Hiroshima 739-8511, Japan
25 Department of Astrophysics, CAB-CSIC/INTA, 28850
Torrej´on de Ardoz, Madrid, Spain
26 Jet Propulsion Laboratory, California Institute of Technol-
ogy, Pasadena, CA, 171-113, USA
27 Department of Physics, University of Cincinnati, Cincin-
nati, OH 45221, USA
28 Center for Extrasolar Planetary Systems, Space Science In-
stitute, 4750 Walnut St, Suite 205, Boulder, CO 80301, USA
29 Department of Astronomical Science, The Graduate Uni-
versity for Advanced Studies, 2-21-1, Osawa, Mitaka, Tokyo,
181-8588, Japan
30 Institute of Astronomy and Astrophysics, Academia Sinica,
P.O. Box 23-141, Taipei 10617, Taiwan
31 Swiss Federal Institute of Technology (ETH Zurich), Insti-
tute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich,
Switzerland
32 Kavli Institute for Physics and Mathematics of the Uni-
verse, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa,
Chiba 277-8568, Japan
33 Department of Cosmosciences, Hokkaido University, Kita-
ku, Sapporo, Hokkaido 060-0810, Japan
34 H. L. Dodge Department of Physics & Astronomy, Univer-
sity of Oklahoma, 440 W Brooks St Norman, OK 73019, USA

2
1. INTRODUCTION
A protoplanetary disk loses almost all of its mass af-
ter a few million years (Haisch et al. 2001; Currie et al.
2009; Cloutier et al. 2014; Ribas et al. 2015), during
which the disk can be perturbed by accretion, jets,
photoevaporation, dust growth, and planet formation
(e.g., Crida & Morbidelli 2007; Armitage 2011). Pre-
vious theoretical simulations predicted gaps within
disks, which is likely related to planet formation (e.g.,
Marsh & Mahoney 1992; Rice et al. 2003; Zhu et al.
2011, 2012). In recent years, dozens of high-spatial
resolution observations have revealed a diversity of
shapes within disks such as gaps, rings, and spiral
features (e.g., Hashimoto et al. 2011; Muto et al. 2012;
ALMA Partnership et al. 2015; P´erez et al. 2016). Ra-
dio observations allow investigation of the gas and dust
distributions of disk and infrared (IR) observations pro-
vide scattered light information from the surface of disks.
Particularly, possible planet-disk interactions for many of
these disk shapes have been suggested (Zhu et al. 2015;
Dong & Fung 2017), as well as other predictions such as
dust sintering (Okuzumi et al. 2016). However, the num-
ber of reported companion candidates within the disks
is much smaller than the number of asymmetric disks
(Quanz et al. 2013; Reggiani et al. 2014; Currie et al.
2015; Sallum et al. 2015; Reggiani et al. 2017). There-
fore continuing explorations of disk and companions is
important for the study of planet formation and disk
evolution mechanisms.
A class of disks having an inner cavity, called tran-
sitional disks, is of particular interest in studying the
disk evolution and dissipation. Some of the transitional
disks are expected to harbor a small inner disk that
is optically thick in optical/near-IR around a central
star and are called pre-transitional disks (Espaillat et al.
2010, 2014). In this paper, we report the result of near
infrared scattered light imaging observations of LkHα
330. LkHα330 is a young stellar ob ject (YSO) in the
Perseus association ((RA,DEC) =(03 45 48.28, +32 24
11.9)). This system exhibits the spectral feature of a pre-
transitional disk (Espaillat et al. 2014) and Brown et al.
(2007) suggested an inner disk by showing polycyclic aro-
matic hydro-carbon features. Furthermore, mm and sub-
mm observations have reported that the disk has a large
(∼0.
′′16–0.
′′27) gap (Brown et al. 2008; Andrews et al.
2011; Isella et al. 2013) and IR observations have sug-
gested spirals (Akiyama et al. 2016). These studies sug-
gest grain growth and possibly unseen planets within the
disk that may cause the large gap and spirals. To follow-
up the earlier studies on this intriguing system we con-
ducted H- and Ks-bands observations of LkHα330 as
a part of the Strategic Explorations of Exoplanets and
Disks with Subaru (SEEDS; Tamura 2009) project.
In this paper we describe our observations and data
reduction in Section 2 and present our results and data
analyses are shown in Section 3. In Section 4 we dis-
cuss the detected features in the disk and summarize our
results.
2. OBSERVATIONS AND DATA REDUCTION
35 Astronomical Institute, Tohoku University, Aoba-ku,
Sendai, Miyagi 980-8578, Japan
The observations and data for LkHα330, which are
analyzed in this study, have been reported previously in
Uyama et al. (2017).
We made H-band (∼1.6 µm) observations of LkHα330
in 2014 October and Ks-band (∼2.2 µm) observations
in 2015 January with Subaru/HiCIAO (Suzuki et al.
2010a) combined with classical AO system AO 188
(Hayano et al. 2008). A typical FWHM of each unsat-
urated point-spread function (PSF) is ∼80 mas in the
H-band and ∼70 mas in the Ks-band. The data of this
study were obtained without a coronagraph for both the
H- and Ks-band observations. Note that Akiyama et al.
(2016) also used Subaru/HiCIAO to observe this system
in 2011 December but adopted a 0.
′′4 coronagraph mask,
which prevents exploration of the gap region of the disk.
The data sets were taken by combining polarization dif-
ferential imaging (PDI) to investigate faint disk struc-
tures and angular differential imaging (ADI) to detect
substellar companions around the central star. Detailed
observation logs are shown in the SEEDS/YSO com-
prehensive report of Uyama et al. (2017), which applied
only ADI reduction (Marois et al. 2006; Lafreniere et al.
2007) for companion explorations. This study focuses
on the data analysis of PDI. We used the “quad-PDI”
(qPDI) mode where two Wollaston prisms enable the ac-
quisition of two ordinary and extraordinary rays on one
frame simultaneously. Each field of view is ∼5′′ × ∼5′′
and the plate scale after distortion correction is 9.5
mas/pix. After the first reduction of flat fielding, dis-
tortion correction, and image registration, all the po-
larimetric data sets were reduced in the same way as
Hashimoto et al. (2011, 2012) using IRAF.
3. RESULTS AND DATA ANALYSIS
3.1. Basic Parameters of LkHα330
LkHα330 was assumed to have 250 pc for a dis-
tance, 3 Myr old for an age, and GIII for a spectral
type (Cohen & Kuhi 1979; Enoch et al. 2006) in the pre-
vious studies introduced in Section 1. However, Gaia
DR2 recently reported the distance to be 311 ±8 pc
(Gaia Collaboration et al. 2016, 2018). Therefore we
adopt the GAIA-measured distance in our discussion.
Herczeg & Hillenbrand (2014) estimated a spectral type
of LkHα330 to be F7.0 by analyzing its optical spec-
tra with an assumed distance of 315 pc. We converted
the spectral type of F7.0 to the effective temperature us-
ing the relationship between a spectral type and effective
temperature in Pecaut & Mamajek (2013). We used B
and V-band magnitudes (Mermilliod 1987) to determine
extinction-corrected V-band magnitude, which was con-
verted to a LkHa 330’s bolometric luminosity based on
Pecaut & Mamajek (2013). These effective temperature
and luminosity described above were compared to the
Pisa pre-main sequence evolution tracks (Tognelli et al.
2011). Finally, we estimate a mass and age of LkHα330
to be 2.8±0.2M⊙and 2.5±0.7 Myr, respectively.
3.2. Polarized Intensity Image
We detected a large gap and spiral-like features with
signal-to-noise (S/N) ratios of >30 at the peak of the ring
and >20 at the peak of the spiral regions. Figure 1 shows
Hand Ksr2-scaled polarization intensity (PI) images.
The PI parameter is dependent on r−2and we scaled

3
Figure 1. Subaru/HiCIAO r2-scaled PI image of LkHα330 in the H- (left) and Ks-bands (right). The scale bar is arbitrary. The SMA
(λ=0.87 mm) observation result is overlaid on both images as gray contours. The levels are the same as those shown in Akiyama et al.
(2016). Perpendicular blue lines in the Ksimage represent semi-major and semi-minor axes. North is up and east is left.
Figure 2. Hand KsPolarization vector maps superimposed on the PI maps.
Figure 3. Polarization position angle errors as a radial profile in
each image.
this parameter by multiplying PI image by r2so that
we can more properly see the structures. We note that
this treatment corresponds to neglecting the disk flaring
when calculating scattering angle, and may be problem-
atic when discussing the disk structures quantitatively
(Stolker et al. 2016). In this paper, we present some
characteristic features on radial and azimuthal profiles
and disk asymmetry of the disk, but keep the discussions
on them at more or less qualitative levels. The contours
taken from the Submillimeter Array (SMA) observation
(λ=0.87 mm) discussed in Akiyama et al. (2016) are su-
perimposed on the figures.
To estimate the S/N ratio, we first measured the po-
larization vector as seen in Figure 2 and defined θerr as
the difference of the angle between the polarization vec-
tor and the vector normal to the position vector mea-
sured from the central star. We then calculated radial
profiles (see Figure 3) and converted the polarization an-
gle error into a polarization error using an equation (6)
in Kwon et al. (2016). In this estimate of the error, we
assume that the ”real” polarization vectors are centro-
symmetric around the central star. The observed polar-

4
Table 1
Adopted parameters of the disk
Parameters Previous study This study
semi-major axis [au]a50b–84c54±1
position angle [degree] 80b91±2
inclination [degree] 35b31±3
Note. — a: Angular separations do not change and thus we
scaled the size reported from previous studies by the distance of
310 pc. b: Brown et al. (2008), c: Andrews et al. (2011)
ization pattern is indeed very close to centro-symmetric
(see Figure 2) and the non-azimuthal polarization such
as T Cha (Pohl et al. 2017) is probably negligible. We
define noise as the standard deviation at given annu-
lar areas like ADI contrast limit (see Section 3.7 and
Uyama et al. 2017).
3.3. Gap Region
We traced the inner wall (hereafter we call this the
“ring”) region in the r2-scaled PI images and then fitted
the peak profiles with an elliptic equation ( x−xcen
a)2+
(y−ycen
b)2= 1, in which aand bare the semi-major axis
and semi-minor axis. Table 1 compares the cavity radius,
position angle of the semi-major axis, and inclination
from previous studies and this work. In the calculation
we used the nonlinear least-squares (NLLS) Marquardt-
Levenberg algorithm implemented into gnuplot. The
error bars represent 1σasymptotic standard error. We
note that previous studies used the midplane of the disk
for measuring the gap while we used the surface bright-
ness of the disk. Observations of transitional disks have
systematically revealed bigger cavity sizes in the mm
continuum than in scattered light (Dong et al. 2012),
e.g., PDS 70 (Hashimoto et al. 2012, 2015) and 2MASS
J1604 (Mayama et al. 2012; Dong et al. 2017). This phe-
nomenon may be explained as being due to mm-sized
dust being filtered out at the cavity edge due to gas-dust
coupling effect (e.g., Rice et al. 2006; Zhu et al. 2012;
Dong et al. 2015b). Here we report that LkHα330 is
another example of this class of object. Andrews et al.
(2011) modeled mm continuum emission of the disk and
concluded that the cavity size is 84 au (0.
′′27; see also
Isella et al. 2013). The NIR cavity size seen by Subaru
is only ∼54 au, much smaller than the mm cavity size.
3.4. Spiral-like Region
As discussed in Akiyama et al. (2016) the two peaks
of the SMA continuum are located at spiral-like features.
Interestingly, the surface and midplane distributions at
the south-west region are consistent, while the north-east
region does not exhibit a similar distribution. Figure 4
shows deprojected and r2-scaled PI images and figures 5
and 6 show polar-projected images taken from Figure 4.
We traced the ridge of the spiral-like structures, which
is superimposed on the images (blue crosses). The mor-
phology of the outer region implies that the disk’s rota-
tion is counter-clockwise. Note that we did not change
the scattering angle when depro jecting the PI images but
changed their inclinations to zero only for the purpose of
tracing the peaks of the outer structures.
We can now see clear deviations from the axisymmetric
ring-like structure at r∼200 mas. There are two spiral
structures: one is launched at about PA=290◦and the
other is at PA=70◦. We find that the H- and Ks-band
observations have different shapes of the outer asymmet-
ric features. For the south-west non-axisymmetric fea-
tures, they extend from PA∼290◦to 180◦both in H- and
Ks-bands, and they appear like ”spiral” features. For the
north-east feature, however, the H-band feature extends
from PA∼70◦to 0◦and it does appear like a ”spiral”,
while in the Ks-band, the emission between PA∼40◦and
0◦is missing. The appearance of the north-east feature
in the Ks-band may be described as ”slightly inclined
blob”. Anyway, the inclined spirals can have complex
morphology (e.g., Dong et al. 2016a) and we discuss the
possibility of the spiral in Section 4.1.2.
We could trace the peaks of the south-west struc-
ture between PA=180◦–270◦in the H-band and between
PA=180◦–290◦in the Ks-band. On the other hand, we
could trace the peaks of the north-east structure between
PA=0◦–70◦in the H-band and between PA=40◦–60◦in
the Ks-band. We investigated angles between the roots
of the spirals and the ring by using the H-band result for
north-east structure and the Ks-band result for south-
west structure. The pitch angles are determined to be
∼12◦and ∼16◦for the south-west and north-east struc-
tures, respectively. These values are similar to the SAO
206462 spirals (Muto et al. 2012).
However, we note a weak tendency from the “spiral
top” toward the other side of disk in Figures 5 and 6,
which possibly represents another mechanism. A trail-
ing spiral behaves as a monotonically increasing profile
(Goldreich & Tremaine 1979). The spiral density wave
is likely to be a trailing feature, and it may be difficult
to explain the blob-like morphology that we see in the
north-east in the Ks-band image. Since previous SMA
and CARMA observations did not report any specific fea-
tures except for the central large gap, identifying these
asymmetric outer structures requires follow-up observa-
tions with a high spatial resolution.
3.5. Azimuthal Profiles
3.5.1. Ring Region
We investigated the surface brightness profiles of the
deprojected image after averaging over 5×5 pix so that
we can expect to reduce the noise at the pixel scale. Fig-
ure 7 shows azimuthal profiles of the deprojected PI im-
ages at separations of r= 0.
′′17 and 0.
′′25. We find that
azimuthal profiles at the ring region (r= 0.
′′17) show
strong wavelength dependence. This is in contrast to the
results of multi-band observations of the disk in other
systems (e.g., Benisty et al. 2017). The south direction
(PA∼180◦) is the brightest in the H-band profile. Con-
sidering that the minor axis of the disk is in the north-
south direction (see Section 3.3), this is probably due to
the excess of forward scattering and therefore the south-
ern side of the disk is likely to be the near side. However,
in the Ks-band, the scattered light is the brightest in the
eastern side, which is along the major axis of the disk.
Such a large variation in the scattered light profiles in
different bands might suggest that the dust distribution
is not azimuthally symmetric. This issue will be further
discussed in Section 4.2.1.
3.5.2. Outer Region

5
Figure 4. Depro jected and r2-scaled H- (left) and Ks-band (right) PI images. We additionally plot traced peaks of the spiral-like structure
in the south-west direction using blue crosses. Note that we have changed the scale bars from those in Figure 1 in order to make the outer
structures clearer.
Figure 5. Polar-projected H-band PI image after deprojection
and scaling by squared separations of r2. The color scale is arbi-
trary. In order to make it easier to find outer asymmetric features,
we started PA from −45◦.
Figure 6. As Figure 5 for the Ks-band.
Our H-band profile at r= 0.
′′25 is different from
Akiyama et al. (2016), particularly at the north region.
The previous observation used the coronagraph mask and
did not explore the central region, while our observa-
tion could explore much inner region. Our profile might
be partially influenced by the asymmetric dust distri-
bution of the ring. We also find that these profiles are
quite different from the ring azimuthal profile, particu-
larly the relative decline of the surface brightness at the
forward scattering region. The spiral-like features ap-
pear at r∼0.
′′3 in Figures 5 and 6 but our data sets
suggest that the r∼0.
′′25 area likely belongs to the outer
spiral-like region.
3.6. Radial Profiles
Figure 8 shows radial profiles between 0.
′′15 and 0.
′′45
in both the H- and Ks-band PI images. These profiles
have azimuthal asymmetry. The PAs 10◦and 230◦cor-
respond to both spiral-like features. 91◦and 271◦cor-
respond to the semi-major axis directions. We used the
least squares method on these profiles and a power-law
to investigate the surface structure of the disk. The fit-
ted powers are listed in Table 2. Except at the ring and
spiral-like regions, the surface brightness is in proportion
to the separation, to the power of no larger than 2, and
is different from a flared disk’s behavior. An r−3profile
can be explained with a flat disk (Momose et al. 2015),
which can produce shadows due to surface structures and
make the surface brightness profiles complex.
Within r < 0.
′′26 the Hand Ksprofiles are similar
but have small difference. This difference may reflect a
difference in the ring’s scattering between the H- and
Ks-bands. In both bands the inner regions (H: ≤40
au, K: ≤45 au) behaves as highly flared disks, which
creates shadows outward (H:50–75 au, K: 55–80 au). By
combining these features we can assume that the Ks-
band ring extends more than the H-band ring.
At the outer region the fitted powers are smaller than
−2 along PA=271◦direction, which suggests that the
disk’s surface in the semi-ma jor axis directions also be-
haves as a flat disk influenced by shadows. PA=91◦pro-
file is the semi-major axis direction but mixed with the
spiral-like structure. In PA=10◦and 230◦directions the
profiles exhibit a more gradual change, with a steep de-
crease at separations greater than r > 0.
′′4. These profiles
are consistent with flaring of the spiral-like structure and
these region may have different dust properties.
3.7. Angular Differential Imaging
As companion exploration, Uyama et al. (2017) con-
ducted an ADI reduction of all the LkHα330 data sets
and could not find any companion candidates around the
central star. Figure 9 shows our ADI-reduced image of
the Ks-band observation. We performed ADI-LOCI re-
duction (Lafreniere et al. 2007) and the algorithm auto-
matically masked a ∼0.
′′15 region from the center. Our
ADI-LOCI pipeline did not work properly for the nearly

6
Figure 7. Azimuthal surface brightness profiles at ∼0.
′′17 (left) and ∼0.
′′25 (right).
Table 2
Power-law fit of radial profiles
PA [degree] H Ks
0.
′′1< r ≤0.
′′15 0.
′′15 ≤r≤0.
′′24 0.
′′24 ≤r≤0.
′′40 0.
′′1< r ≤0.
′′18 0.
′′18 ≤r≤0.
′′26 0.
′′26 ≤r≤0.
′′40
10 -0.44 -4.1 -0.65 -0.10 -5.4 -6.5×10−2
91 -1.2 -5.1 -0.91 -1.2 -4.6 -0.70
230 -5.0×10−2-3.5 -1.0 7.8×10−3-4.6 -0.33
271 -6.5×10−2-2.9 -7.0 9.0×10−2-2.4 -5.2
face-on disk, resulting in artificial residual pattern as seen
in Figure 9. Therefore, one cannot discuss the mor-
phology of the disk in the ADI-LOCI reduced image.
Nonetheless, the image can be used to constrain the flux
from a possible point-like source. Some signals remain
around the central star but their S/N ratios of them are
less than 5 and therefore we regard them as being resid-
ual from the PSF subtraction.
The contrast limits have already been described in
Uyama et al. (2017), and were converted into mass lim-
its based on the COND03 model (Baraffe et al. 2003).
Figure 10 shows the mass limit of our observations. We
have set constraints on the mass of potential companions
in the disk down to ∼20 MJ. The shadows correspond to
errors of our age estimation. The conversion was based
on the “hot-start” model (BT-Settl; Allard et al. 2011).
Besides age, planet mass limits could also be uncer-
tain due to assumed planet luminosity evolution models.
“Hot-start” evolutionary models such as those we adopt
are often associated with disk instability formation.
“Cold-start” models (Marley et al. 2007) attempt to
model planet formation by core accretion and yield lower
initial entropies and luminosities and thus higher masses
for a given contrast limit (though see Berardo et al.
2017). However, demographics suggest that companions
with these masses/mass ratios and separations detectable
from our data are likely not planets formed by core accre-
tion (Brandt et al. 2014; Currie et al. 2011). Thus, our
mass limits are likely to probe only companions formed
like binary stars or by disk instability.
4. DISCUSSIONS
The disk around the LkHα330 has complex morphol-
ogy. In this section, we focus on disk features one by
one and discuss the implications on the disk properties,
which will help to synthetically model the disk and to in-
vestigate disk evolution mechanisms such as gap opening
and spiral forming with unseen planets.
4.1. Morphology
4.1.1. Gap
Previous observations of LkHα330 suggested planet
formation within the gap (e.g., Zhu et al. 2012;
Isella et al. 2013). Our ADI reduction could not fully ex-
plore the gap region and thus planet formation remains
a plausible but unconfirmed scenario.
Grain growth (e.g., Birnstiel et al. 2012) and disk wind
(e.g., Suzuki et al. 2010b) are also possible mechanisms
for opening the gap in the disk. A spectral feature of
LkHa 330 is an excess at the mm and sub-mm wave-
length ranges (Brown et al. 2008; Hitchcock in prep.),
which suggests the existence of larger dust and supports
the possibility of grain growth. Investigating disk wind
will require follow-up observations of gas kinematics; the
presence of disk wind is suggested if blue-shift compo-
nents excel in the data. Although photoevaporation can
produce a gap within the disk (e.g., Clarke et al. 2001;
Goto et al. 2006; Owen et al. 2011), the disk mass is
much larger (Mdisk ∼0.01M⋆≥0.02M⊙; Andrews et al.
2011) than expected mass of the photoevaporation stage
(an order of 0.001M⊙; Alexander et al. 2006).
4.1.2. Spiral-like Structures

7
Figure 8. Radial profiles in the H- and Ks-band data sets. The gray lines are power-law-fit results at three separations. The fitted results
are shown in Table 2.

8
Figure 9. ADI-reduced image in the Ks-band. North is up and
the central star is masked by the algorithm.
Figure 10. Mass limits of the ADI-reduced images. The vertical
axis is mass in MJunit and the horizontal axis is the projected
separation. We converted the contrast limit into mass units by the
BT-Settl model assuming that possible companions can clear the
gas and dust locally and that the conversion can ignore extinction
from the disk.
The LkHα330 system may be another disk, after
SAO 206462 (Muto et al. 2012), MWC 758 (Grady et al.
2013), HD 100453 (Wagner et al. 2015), DZ Cha
(Canovas et al. 2018) (note that the inner disk in the AB
Aur system, Hashimoto et al. 2011, has also been sug-
gested to host two spiral arms, Figure 14 in Dong et al.
2016a), that has been discovered to have a pair of
nearly symmetric spiral arms in scattered light. Ex-
cept for HD 100453, which has an M dwarf companion
that is probably driving the arms (Dong et al. 2016b;
Wagner et al. 2018), the origin of the spiral arms in
the other systems is under debate. Two mechanisms
are proposed to explain the morphology of these near
m= 2 arms: gravitational instability (e.g., Dong et al.
2015a), and companion-disk interaction (e.g., Dong et al.
2015a; Zhu et al. 2015). As LkHα330’s disk mass is
perhaps too low to trigger the gravitational instabil-
ity (Mdisk ∼0.01M⋆; Andrews et al. 2011), we consider
companion-disk interactions to constitute a plausible sce-
nario.
We carried out three-dimensional hydrodynamics and
radiative transfer simulations to produce synthetic im-
ages of a pair of planet-induced spiral arms in scattered
light that qualitatively match the Subaru observations
of LkHα330, as shown in Figure 11. The simulation
was conducted based on the planetary-mass-companion
model in Dong et al. (2016a), and is briefly described
here. We use the hydrodynamics code PENGUIN (Fung
2015) to calculate the density structure of a disk per-
turbed by a planet in a circular orbit at 100 au. The
resulting disk structure is translated into near-IR polar-
ized light images using the radiative transfer code HO-
CHUNK3D (Whitney et al. 2013). The planet’s mass
was Mplanet = 0.003M⋆, which corresponds to ∼6MJin
LkHα330. The synthetic image was produced assuming
the object is 310 pc away, and under the actual viewing
angle of the system, PA = 90◦and inclination i= 30◦.
The image was convolved by a Gaussian PSF to achieve
an angular resolution of 0.
′′06. The outer disk exterior to
the planet’s orbit was removed in post-processing. The
model image matches the actual data well, which sug-
gests that the two spiral arms in LkHα330 may be in-
duced by a 5–10MJplanet at ∼120 AU (0.
′′4). At the
current epoch, the planet may be at PA ∼20◦. Note that
these simulations focus on reconstructing a pair of spi-
rals in the LkHα330’s disk and are separate from those
reported in Isella et al. (2013) that predicted unseen pro-
toplanets within the gap region.
4.2. Color Discussion
We have observed LkHα330 in the H- and Ks-bands
and can discuss a disk variation in wavelength. In this
section we focus on the difference between the azimuthal
profile of the ring shown in Figure 12 and a color map of
the disk.
4.2.1. Scattering Properties
We investigated phase functions of a grain-scattering
model in Figure 12 using equations (8) and (9) in
Graham et al. (2007), where we fixed the polarization
parameter of pmax to 1. We put four dotted lines in each
graph by changing the scattering parameter of gand a
coefficient of the phase function in order to compare the
phase functions to the ring profiles. A formula of the
phase function is given by
∝1−g2
4π(1 + g2−2gcos θsin i)3/2·pmax
1−cos2θsin2i
1 + cos2θsin2i,
where θis a scattering angle and iis an inclination. Fig-
ure 13 is a polar diagram of Henyey-Greenstein phase
function (Φ(a) = 1−g2
4π(1+g2−2gcos(a))3/2, where ais a phase
angle; Henyey & Greenstein 1941) by changing gfrom 0
to 0.6, which shows the dependency of scattering angle
on the phase function. Forward scattering angle is given
by π/2−i−βwhere βis an opening angle of the disk
(see figure 9 in Jang-Condell 2017). We assume that
the disk is geometrically thin and βis negligible. Our
adopted phase functions partially deviate from the az-
imuthal profiles of the ring. These phase functions have
similar profiles at the brightest region. The H-band func-
tions with g > 0.5 may be more suitable for the profile
at PA∼90◦–270◦, while g= 0 fits the profile at PA∼90◦
in the Ks-band. However, these functions do not fully
agree with the ring profiles. Apparently at the north
region (PA∼0◦) both rings are much brighter than the

9
Figure 11. Comparison of r2-scaled surface brightness of outer structures in the H-band (left), Ks-band (middle), and model (right)
images. The color bars are arbitrary. We overlay an r= 0.
′′2 mask on all the images because the model calculation focuses on reproducing
only the outer features.
expected phase functions and Ks-band azimuthal profile
three peaks, which cannot be reproduced by a simple
phase function we adopt and may suggest the ring has
non-axisymmetric distribution of dust and/or composi-
tion.
In order to investigate whether such large varia-
tions of the scattering properties with a simple dust
model, we run a Mie scattering code attached to the
HO-CHUNK radiative transfer code (Bohren & Huffman
1983; Whitney et al. 2003) assuming the astronomical
silicates model (Laor & Draine 1993). When we defined
the dust size so as to reproduce the Ks-band g= 0 value
by changing minimum dust size between 1 nm and 300
nm, the gvalue in the H-band was automatically defined
and was always smaller than 0.5. This result indicates
that the ring profiles cannot be described by a simple
dust species distributed all over the entire disk. Our
assumptions and calculations could not characterize the
disk fully but might set particular constraints on the dust
distribution.
Explaining these variations requires non-axisymmetric
pattern of size, density, and composition distributions
and vertical structures. As ALMA revealed that MWC
758 has complexity in its ring (Boehler et al. 2018), ra-
dio interferometric observations will help to reveal dust
size and density distributions. Identifying its composi-
tion requires follow-up observations in other bands, e.g.,
with JWST/MIRI (Wells et al. 2015) or TMT/MICHI
(Sakon et al. 2014). A future integral field spectroscopy
(IFS) in mid-IR wavelength can constrain abundance
of polycyclic aromatic hydrocarbon and silicate. The
wavelength difference of the azimuthal surface brightness
structures shown in Figure 12 may not be simply ex-
plained by the azimuthal variations of the vertical struc-
tures and therefore investigating synthetic dust distribu-
tions will be necessary.
4.2.2. Color Map
Figure 14 shows a color map of the disk generated by
dividing the Ks-band PI image by the H-band PI image.
In this process the Ks-band image is convolved in order
to fit the Ks-band’s PSF to the H-band’s PSF. AO188
worked effectively enough to suppress both PSF’s wings
and the H-band PSF’s core is broader as mentioned in
Section 2. We then re-registered two PDI-reduced images
by defining the center as the elliptical-fit results of the
ring. Finally we normalized the Ks/HPI image by the
Ks/H luminosity of the central star (=2.27 from UCAC4
catalog; Zacharias et al. 2012).
We find that the disk is basically “blue”. This implies
that the typical dust size is small enough for Rayleigh
scattering. However, there are seen some ”redder” re-
gions at (ρ,PA)=(∼0.
′′3, 0◦–30◦) and (0.
′′15–0.
′′4, 45◦–
90◦). The northern part (∼0.
′′3, ∼0◦–30◦) is influenced
by the north-east spiral-like feature that appears only in
the H-band image (see Figures 4, 5, and 6). The in-
ner eastern part (0.
′′15–0.
′′2, 45◦–90◦) corresponds to the
wavelength-difference of the azimuthal profiles, which is
discussed in Section 4.2.1.
The outer eastern part (0.
′′2–0.
′′4, 45◦–90◦) comes from
the lack of an outer scattering area in the H-band
disk. The H-band PI image previously reported in
(Akiyama et al. 2016), which is presented as a r2-scaled
PI image in Figure 16, looks like the Ks-band image.
A comparison of the FWHMs of the previous and our
H-band image shows that our data sets had better AO
efficiency. Therefore our data reduction shows a “red”
region at the outer north-east region. This phenomenon
demonstrates that a possibility of “a directional shadow”
is plausible; namely, when we observed this system, an
inner object occasionally partially veiled starlight and
cast a shadow onto the north-east region of the disk. We
consider a clump-like object moving in the very inner
region. If the orbit of the object is highly misaligned
with the outer disk, we can explain the change of outer
morphology over the 3 months. The orbital separation
is expected to be very near (≤1 au) the central star. Re-
garding the possibility of there being an inner clump, we
refer to CVSO 30 and “dipper” stars. CVSO 30 was re-
ported to harbor a close-in protoplanet candidate based
on transit observations (CVSO 30 b; van Eyken et al.
2012). However, follow-up observations suggested that
the companion candidate is a clump rather than a planet
(Onitsuka et al. 2017). Dipper YSOs revealed by the K2
survey suggest the existence of occulting structures lo-
cated at quite small separations (Ansdell et al. 2016).
Particularly, Ansdell et al. (2016) reported RX J1604.3-
2130A to be a dipper star. This YSO has a face-on disk
with a large gap (e.g., Mayama et al. 2012). Therefore an
inner clump-like object with an orbit highly misaligned
to the outer disk is a possible scenario.
Another possible mechanism of casting shadow in the
outer disk is the existence of an inner disk. Previous disk
observations have revealed shadows on the protoplane-
tary disks induced by inner objects (Garufi et al. 2014;
Pinilla et al. 2015; Canovas et al. 2017; Stolker et al.
2016, 2017; Benisty et al. 2017; Debes et al. 2017). If
LkHα330 has an inner disk that can cast shadows on

10
Figure 12. Azimuthal surface brightness profiles of the deprojected ring region (r∼0.
′′17) in the H-band(left) and Ks-band (right). We
include expected phase functions assuming a uniform dust distribution in the disk.
Figure 13. Polar diagram of Henyey-Greenstein phase function.
The phase angle corresponds to a deviation from the forward-
scattering direction. The radial scale is arbitrary.
the outer disk, non-axisymmetric structures can be ob-
served (Facchini et al. 2018). From the models presented
in Long et al. (2017), we consider that the difference of
the inclination between the inner and the outer disks
is as small as <10◦in order to produce the azimuthal
features observed in H-band. Given that our Ks-band
image, which was taken just 3 months after the H-band
image, however, this rapid change of the shadow feature
can hardly be explained by the change of the orientation
of the inner disk because we do not expect rapid (on the
timescale comparable to Kepler timescale) precession of
the inner disk. The inner disk should have a particular
extinction property to let Ks-band wavelength transmit.
As multi-band observations of HD 100453 (Benisty et al.
2017) did not show clear difference of the shadow struc-
tures, we consider that the shadowing by the inner disk
is unlikely.
In order to investigate this scenario follow-up obser-
vations are required. If the PI signal is detected again
as reported in Akiyama et al. (2016), a clump-like ob-
ject scenario is plausible. However, if follow-up obser-
vations fail to detect a PI signal, other scenarios should
be considered, such as asymmetric dust distribution or
Figure 14. Color map of the LkHα330 disk. The scale bar
represents the PI ratios Ks/H such that red represents a larger
value.
difference of dust properties between the outer and inner
disks.
The authors thank David Lafreni`ere for generously
providing the source code for the LOCI algorithm. The
authors would like to thank the anonymous referees for
their constructive comments and suggestions to improve
the quality of the paper. This research is based on
data collected at the Subaru Telescope, which is op-
erated by the National Astronomical Observatories of
Japan. Based in part on data collected at Subaru tele-
scope and obtained from the SMOKA, which is operated
by the Astronomy Data Center, National Astronomical
Observatory of Japan. Data analysis were carried out
on common use data analysis computer system at the
Astronomy Data Center, ADC, of the National Astro-
nomical Observatory of Japan. This research has made
use of NASA’s Astrophysics Data System Bibliographic
Services. This research has made use of the SIMBAD
database, operated at CDS, Strasbourg, France. This

11
research has made use of the VizieR catalogue access
tool, CDS, Strasbourg, France. The original description
of the VizieR service was published in A&AS 143, 23.
This work was supported by JSPS KAKENHI Grant
Numbers JP17J00934, JP15H02063, JP258826.
The authors wish to acknowledge the very significant
cultural role and reverence that the summit of Mauna
Kea has always had within the indigenous Hawaiian com-
munity. We are most fortunate to have the opportunity
to conduct observations from this mountain.
REFERENCES
Akiyama, E., Hashimoto, J., Liu, H. B., et al. 2016, AJ, 152, 222
Alexander, R. D., Clarke, C. J., & Pringle, J. E. 2006, MNRAS,
369, 229
Allard, F., Homeier, D., & Freytag, B. 2011, in Astronomical
Society of the Pacific Conference Series, Vol. 448, 16th
Cambridge Workshop on Cool Stars, Stellar Systems, and the
Sun, ed. C. Johns-Krull, M. K. Browning, & A. A. West, 91
ALMA Partnership, Brogan, C. L., P´erez, L. M., et al. 2015,
ApJL, 808, L3
Andrews, S. M., Wilner, D. J., Espaillat, C., et al. 2011, ApJ,
732, 42
Ansdell, M., Gaidos, E., Rappaport, S. A., et al. 2016, ApJ, 816,
69
Armitage, P. J. 2011, ARA&A, 49, 195
Baraffe, I., Chabrier, G., Barman, T. S., Allard, F., & Hauschildt,
P. H. 2003, A&A, 402, 701
Benisty, M., Stolker, T., Pohl, A., et al. 2017, A&A, 597,
doi:10.1051/0004-6361/201629798
Berardo, D., Cumming, A., & Marleau, G.-D. 2017, ApJ, 834, 149
Birnstiel, T., Andrews, S. M., & Ercolano, B. 2012, A&A, 544,
A79
Boehler, Y., Ricci, L., Weaver, E., et al. 2018, ApJ, 853, 162
Bohren, C. F., & Huffman, D. R. 1983, Absorption and scattering
of light by small particles
Brandt, T. D., McElwain, M. W., Turner, E. L., et al. 2014, ApJ,
794, 159
Brown, J. M., Blake, G. A., Qi, C., Dullemond, C. P., & Wilner,
D. J. 2008, ApJL, 675, L109
Brown, J. M., Blake, G. A., Dullemond, C. P., et al. 2007, ApJL,
664, L107
Canovas, H., Hardy, A., Zurlo, A., et al. 2017, A&A, 598,
doi:10.1051/0004-6361/201629145
Canovas, H., Montesinos, B., Schreiber, M. R., et al. 2018, A&A,
610, doi:10.1051/0004-6361/201731640
Clarke, C. J., Gendrin, A., & Sotomayor, M. 2001, MNRAS, 328,
485
Cloutier, R., Currie, T., Rieke, G. H., et al. 2014, ApJ, 796, 127
Cohen, M., & Kuhi, L. V. 1979, ApJS, 41, 743
Crida, A., & Morbidelli, A. 2007, MNRAS, 377, 1324
Currie, T., Cloutier, R., Brittain, S., et al. 2015, ApJL, 814, L27
Currie, T., Lada, C. J., Plavchan, P., et al. 2009, ApJ, 698, 1
Currie, T., Burrows, A., Itoh, Y., et al. 2011, ApJ, 729, 128
Debes, J. H., Poteet, C. A., Jang-Condell, H., et al. 2017, ApJ,
835, doi:10.3847/1538-4357/835/2/205
Dong, R., & Fung, J. 2017, ApJ, 835, 146
Dong, R., Fung, J., & Chiang, E. 2016a, ApJ, 826, 75
Dong, R., Zhu, Z., Fung, J., et al. 2016b, ApJL, 816, L12
Dong, R., Zhu, Z., Rafikov, R. R., & Stone, J. M. 2015a, ApJL,
809, L5
Dong, R., Zhu, Z., & Whitney, B. 2015b, ApJ, 809, 93
Dong, R., Rafikov, R., Zhu, Z., et al. 2012, ApJ, 750, 161
Dong, R., van der Marel, N., Hashimoto, J., et al. 2017, ApJ, 836,
201
Enoch, M. L., Young, K. E., Glenn, J., et al. 2006, ApJ, 638, 293
Espaillat, C., D’Alessio, P., Hern´andez, J., et al. 2010, ApJ, 717,
441
Espaillat, C., Muzerolle, J., Najita, J., et al. 2014, Protostars and
Planets VI, 497
Facchini, S., Juh´asz, A., & Lodato, G. 2018, MNRAS, 473, 4459
Fung, J. 2015, PhD thesis, University of Toronto, Canada
Gaia Collaboration, Brown, A. G. A., Vallenari, A., et al. 2018,
ArXiv e-prints, arXiv:1804.09365
Gaia Collaboration, Prusti, T., de Bruijne, J. H. J., et al. 2016,
A&A, 595, doi:10.1051/0004-6361/201629272
Garufi, A., Quanz, S. P., Schmid, H. M., et al. 2014, A&A, 568,
doi:10.1051/0004-6361/201424262
Goldreich, P., & Tremaine, S. 1979, ApJ, 233, 857
Goto, M., Usuda, T., Dullemond, C. P., et al. 2006, ApJ, 652, 758
Grady, C. A., Muto, T., Hashimoto, J., et al. 2013, ApJ, 762, 48
Graham, J. R., Kalas, P. G., & Matthews, B. C. 2007, ApJ, 654,
595
Haisch, Karl E., J., Lada, E. A., & Lada, C. J. 2001, ApJ, 553,
L153
Hashimoto, J., Tamura, M., Muto, T., et al. 2011, ApJL, 729, L17
Hashimoto, J., Dong, R., Kudo, T., et al. 2012, ApJL, 758, L19
Hashimoto, J., Tsukagoshi, T., Brown, J. M., et al. 2015, ApJ,
799, 43
Hayano, Y., Takami, H., Guyon, O., et al. 2008, in Society of
Photo-Optical Instrumentation Engineers (SPIE) Conference
Series, Vol. 7015, Society of Photo-Optical Instrumentation
Engineers (SPIE) Conference Series, 10
Henyey, L. G., & Greenstein, J. L. 1941, ApJ, 93, 70
Herczeg, G. J., & Hillenbrand, L. A. 2014, ApJ, 786, 97
Hitchcock, T. in prep.
Isella, A., P´erez, L. M., Carpenter, J. M., et al. 2013, ApJ, 775, 30
Jang-Condell, H. 2017, ApJ, 835, 12
Kwon, J., Tamura, M., Hough, J. H., Nagata, T., & Kusakabe, N.
2016, AJ, 152, 67
Lafreniere, D., Marois, C., Doyon, R., Nadeau, D., & Artigau, E.
2007, ApJ, 660, 770
Laor, A., & Draine, B. T. 1993, ApJ, 402, 441
Long, Z. C., Fernandes, R. B., Sitko, M., et al. 2017, ApJ, 838, 62
Marley, M. S., Fortney, J. J., Hubickyj, O., Bodenheimer, P., &
Lissauer, J. J. 2007, ApJ, 655, 541
Marois, C., Lafreniere, D., Doyon, R., Macintosh, B., & Nadeau,
D. 2006, ApJ, 641, 556
Marsh, K. A., & Mahoney, M. J. 1992, ApJ, 395, L115
Mayama, S., Hashimoto, J., Muto, T., et al. 2012, ApJL, 760, L26
Mermilliod, J. C. 1987, Astronomy and Astrophysics Supplement
Series, 71, 413
Momose, M., Morita, A., Fukagawa, M., et al. 2015, PASJ, 67, 83
Muto, T., Grady, C. A., Hashimoto, J., et al. 2012, ApJL, 748,
L22
Okuzumi, S., Momose, M., Sirono, S.-i., Kobayashi, H., &
Tanaka, H. 2016, ApJ, 821, 82
Onitsuka, M., Fukui, A., Narita, N., et al. 2017, PASJ, 69, L2
Owen, J. E., Ercolano, B., & Clarke, C. J. 2011, MNRAS, 412, 13
Pecaut, M. J., & Mamajek, E. E. 2013, ApJS, 208, 9
P´erez, L. M., Carpenter, J. M., Andrews, S. M., et al. 2016,
Science, 353, 1519
Pinilla, P., de Boer, J., Benisty, M., et al. 2015, A&A, 584,
doi:10.1051/0004-6361/201526981
Pohl, A., Sissa, E., Langlois, M., et al. 2017, A&A, 605, A34
Quanz, S. P., Amara, A., Meyer, M. R., et al. 2013, ApJL, 766, L1
Reggiani, M., Quanz, S. P., Meyer, M. R., et al. 2014, ApJL, 792,
L23
Reggiani, M., Christiaens, V., Absil, O., et al. 2017, ArXiv
e-prints, arXiv:1710.11393
Ribas, ´
A., Bouy, H., & Mer´ın, B. 2015, A&A, 576,
doi:10.1051/0004-6361/201424846
Rice, W. K. M., Armitage, P. J., Wood, K., & Lodato, G. 2006,
MNRAS, 373, 1619
Rice, W. K. M., Wood, K., Armitage, P. J., Whitney, B. A., &
Bjorkman, J. E. 2003, MNRAS, 342, 79
Sakon, I., Sakon, I., Honda, M., et al. 2014, in TMT in the
Astronomical Landscape of the 2020s, Thirty Meter Telescope
Science Forum, held 16-19 July, 2014 in Tucson Arizona. Online
at ¡A href=”http://conference.ipac.caltech.edu/tmtsf2014/”¿
http://conference.ipac.caltech.edu/tmtsf2014/¡/A¿, id. 22
Sallum, S., Follette, K. B., Eisner, J. A., et al. 2015, Nature, 527,
342
Stolker, T., Dominik, C., Avenhaus, H., et al. 2016, A&A, 595,
doi:10.1051/0004-6361/201528039
Stolker, T., Sitko, M., Lazareff, B., et al. 2017, ApJ, 849,
doi:10.3847/1538-4357/aa886a
Suzuki, R., Kudo, T., Hashimoto, J., et al. 2010a, in Proc. SPIE,
Vol. 7735, 30
Suzuki, T. K., Muto, T., & Inutsuka, S.-i. 2010b, ApJ, 718, 1289

12
Tamura, M. 2009, 1158, 11
Tognelli, E., Prada Moroni, P. G., & Degl’Innocenti, S. 2011,
A&A, 533, A109
Uyama, T., Hashimoto, J., Kuzuhara, M., et al. 2017, AJ, 153,
106
van Eyken, J. C., Ciardi, D. R., von Braun, K., et al. 2012, ApJ,
755, 42
Wagner, K., Apai, D., Kasper, M., & Robberto, M. 2015, ApJL,
813, L2
Wagner, K., Dong, R., Sheehan, P., et al. 2018, ApJ, 854, 130
Wells, M., Pel, J.-W., Glasse, A., et al. 2015, PASP, 127, 646
Whitney, B. A., Robitaille, T. P., Bjorkman, J. E., et al. 2013,
ApJS, 207, 30
Whitney, B. A., Wood, K., Bjorkman, J. E., & Wolff, M. J. 2003,
ApJ, 591, 1049
Zacharias, N., Finch, C. T., Girard, T. M., et al. 2012, VizieR
Online Data Catalog, 1322
Zhu, Z., Dong, R., Stone, J. M., & Rafikov, R. R. 2015, ApJ, 813,
88
Zhu, Z., Nelson, R. P., Dong, R., Espaillat, C., & Hartmann, L.
2012, ApJ, 755, 6
Zhu, Z., Nelson, R. P., Hartmann, L., Espaillat, C., & Calvet, N.
2011, ApJ, 729, doi:10.1088/0004-637X/729/1/47
APPENDIX
ERROR MAP OF POLARIZATION ANGLE
Figure 15, which is made from Figure 2, shows angle error maps in the H- and Ks-bands. These maps are used
for calculating noise profiles of the PI images and details are explained in Section 3. Yellow corresponds to larger
difference from a centro-symmetric pattern of the polarization vectors and causes larger noise in the PI image.
Figure 15. Angle error maps of the H- (left) and Ks-band (right) images. These maps are used for calculating radial noise of the PI
images, which is described in Section 3.
COMPARISON OF OUR RESULTS WITH THE PREVIOUS HICIAO IMAGE
Figure 16 compares our HiCIAO observations with the previous HiCIAO observation that was originally presented
in Akiyama et al. (2016). Our data sets achieved better AO efficiency and are explained in Section 2.
Figure 16. r2-scaled PI images in the H-band taken in 2014 (left), the Ks-band taken in 2015 (center), and the H-band taken in 2011
(right). The right image is masked with a 0.
′′2-radius mask.