Non-axisymmetric structure in million-year-old discs around intermediate-mass stars

Transcription

1 Non-axisymmetric structure in million-year-old discs around intermediate-mass stars Misato Fukagawa (NAOJ) C. A. Grady, J. P. Wisniewski, Y. Ohta, M. Momose, Y. Matura, T. Kotani, Y. Okamoto, J. Hashimoto, T. Muto, M. Sitko, K. Follette, M. Bonnefoy, N. Kusakabe, M. Tamura, SEEDS/HiCIAO/IRCS/AO188 Collaboration

2 Proto-planetary discs in this talk: discs around ~2 solar-mass stars Compared to TTS Higher frequency of giant planets (e.g., Johnson et al. 2010) Planets detected in direct imaging HR 8799, β Pic, HD Marois et al. (2010) Lagrange et al. (2010) Rameau et al. (2013)

3 Proto-planetary discs in this talk 0.1 Myr Age: 1 10 Myr Herbig Ae/Fe stars (F, A-type) T eff = K M * 2 M 1 Myr Optically thick (L IR /L * Nearby, isolated 0.1), gaseous Single stars; companions not known at the time of target selection 10 Myr 100 Myr NAOJ

4 Scattered-light imaging in near-infrared For optically thick discs, Sensitive to dust in the upper surface of the disc Grains with high scattering efficiency small, (sub- )micron dust 1. Dust sedimentation toward the mid-plane 2. Temperature structure AU

5 Disc imaging with Subaru 1. Higher angular resolution Adaptive optics ( seeing 0.6 ) ~0.07 at 1.6 m 10 AU at 140 pc 28 AU at 400 pc 2. Inner region Polarization differential imaging Inner working radius ~ AU at 140 pc 80 AU at 400 pc Observable = polarized intensity

6 No gaps Variable shadowing? 0.5 =70 AU NIR, thermal shadowing Scattered light was detected when the system is fainter in near-infrared thermal emission. dust growth and sedimentation Kusakabe et al. (2012)

7 Gapped Spiral arms within ~100 AU Two arms seem common Spirals preferentially found for warm (>6000 K) discs? 50 AU 50 AU South Muto et al. (2012) Grady et al. (2013)

8 Gapped Spiral arms within ~100 AU Two arms seem common Spirals preferentially found for warm (>6000 K) discs? 50 AU South Garufi et al. (2013) Benisty et al. (2015) (de-projected, multiplied by r 2 )

9 Gapped Arm-like structure, non-axisymmetry within ~100 AU Evidence of spiral is weaker, but still not axi-symmetric. 100 AU Ohta et al. (submitted.) 100 AU Follette et al. (2014) Momose et al. (2015), Quanz et al. (2013)

10 V1247 Ori: one-armed spiral? Inner disk at 0.2 AU + gap to 46 AU. Companion with the mass ratio, q > ~0.1, is excluded. An arc or a spiral with small pitch angle at 108 AU. 0.2 =77 AU Ohta et al. submitted. (de-projected, multiplied by r 2 ) Kraus et al. (2013)

11 Gapped Arm-like structure beyond 200 AU Large-scale arms seem to disks with remnant envelopes Sometimes, the arm was detected in CO (Tang et al. 2012, Christiaens et al. 2014) Massive, long-lived disc? Hashimoto et al. (2011)

12 Gapped Arm-like structure beyond 200 AU Large-scale arms seem to disks with remnant envelopes Sometimes, the arm was detected in CO (Tang et al. 2012, Christiaens et al. 2014) Massive, long-lived disc? Tang et al. (2012) 1000 AU 280 AU Grady et al. (1999)

13 Gapped Arm-like structure beyond 200 AU Large-scale arms seem to disks with remnant envelopes Sometimes, the arm was detected in CO (Tang et al. 2012, Christiaens et al. 2014) Massive, long-lived disc? AU 100 AU Ardila et al. (2007) Boccaletti et al. (2013)

14 Companions with extreme mass ratio Intermediate-mass stars w/o protoplanetary disks in Sco-Cen (10 20 Myr) q~ Hinkley et al. (2015)

15 Summary Over 10 discs around Herbig Ae stars were directly imaged in scattered light with <0.1 (<14 40 AU) resolution with 8-m class telescopes. Most discs with large (>10 AU) gaps show distinct non-axisymmetry, suggesting presence of companions probably with extreme mass ratio. Non-gapped disks are variable with time in scattered-light, suggesting that their dust discs are already settled. Formation of planets/(sub)stellar companions may occur before 1 Myr. Important to observe discs at < 1 Myr. Companion search in 1 30 AU with mass ratio < 0.1 will be important.