星形成ゼミ
1~8
On the mass segregation of cores and stars 1 Hayley L. Alcock and Richard J. Parker*†分子雲コアが中心集中しているが、前主系列星はそうではない=>分子雲コアが分裂してそうなるのではなく、dynamical evolutionでそうなるやったこと:分子雲とその分裂片のトイモデルを作ってdynamical evolutionで観測を再現できるかどうか確かめた(^ MSRを評価した) CMF(IMF)を再現するように、 300個のコアを用意して、それが710~1100個に分裂するまで計算を続けた
Random fragmentation:コアがランダムに1~5個(同じ質量)に分裂Low-mass fragmentation:軽いコア(<1Mo)が1~5個に分裂High-mass fragmentation:思いコア(>1Mo)が1~5に分裂Migrationは最大で0.5 pc Fragmentsが移動(dynamical ejectionを再現) Amsr = \ +σ5/6/ l subset 〈 l average -O 1/6/ I subset MSR: Mass Segregation Ratio >1:中心集中している<1:離散的
コアがsegregateしてrandom fragmentation/migrationもっとも重いfragments ^msr
(fragments)
Exploring the formation pathways of formamide near young O-type stars V. Allen 1,2,3 , F.F.S. van der Tak ²,3 , A. López-Sepulcre 4,5 , Á. Sánchez-Monge 6 , V.M. Rivilla 7 , and R. Cesaroni7 ¹ NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA; ² Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, the Netherlands; ³ SRON, Landleven 12, 9747 AD Groningen, the Netherlands; 4 CNRS, IPAG, Univ. Grenoble Alpes, F-38000 Grenoble, France; 5 IRAM, 300 rue de la Piscine, 38406 Saint-Martin d’ Hères, France; 6 I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany; 7 INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Florence, Italy E-mail contact: veronica.a.allen at nasa.gov Context. As a building block for amino acids, formamide (NH 2 CHO) is an important molecule in astrobiology and astrochemistry, but its formation path in the interstellar medium is not understood well. Aims. We aim to find empirical evidence to support the chemical relationships of formamide to HNCO and H 2 CO. Methods.  We examine high angular resolution (～0′.2) Atacama Large Millimeter/submillimeter Array (ALMA) maps of six sources in three high-mass star-forming regions and compare the spatial extent, integrated emission peak position, and velocity structure of HNCO and H 2 CO line emission with that of NH 2 CHO by using moment maps. Through spectral modeling, we compare the abundances of these three species. Results. In these sources, the emission peak separation and velocity dispersion of formamide emission is most often similar to HNCO emission, while the velocity structure is generally just as similar to H 2 CO and HNCO (within errors). From the spectral modeling, we see that the abundances between all three of our focus species are correlated, and the relationship between NH 2 CHO and HNCO reproduces the previously demonstrated abundance relationship. Conclusions. In this first interferometric study, which compares two potential parent species to NH 2 CHO, we find that all moment maps for HNCO are more similar to NH 2 CHO than H 2 CO in one of our six sources (G24 A1). For the other five sources, the relationship between NH 2 CHO, HNCO, and H 2 CO is unclear as the different moment maps for each source are not consistently more similar to one species as opposed to the other. Accepted by A&A http://arxiv.org/pdf/1912.11883アストロバイオロジー/ケミストリーにおいて重要な分子種のALMAを用いた観測2 Are Inner Disc Misalignments Common?  ALMA Reveals an Isotropic Outer Disc In- clination Distribution for Young Dipper Stars M. Ansdell 1,2,3 , E. Gaidos 4 , C. Hedges 5 , M. Tazzari 6 , A.L. Kraus 7 et al. 1 Center for Integrative Planetary Science, University of California at Berkeley, Berkeley, CA 94720, USA; ² De- partment of Astronomy, University of California at Berkeley, Berkeley, CA 94720, USA; ³ Flatiron Institute, Simons Foundation, 162 Fifth Ave, New York, NY 10010, USA; 4 Department of Earth Sciences, University of Hawai'i at Mañoa, Honolulu, HI, USA; 5 NASA Ames Research Center, Moffett Blvd, Mountain View, CA 94035, USA; 6 Insti- tute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA, Cambridge, UK; 7 Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA E-mail contact: mansdell at flatironinstitute.org Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tens of percent.  A standard explanation is that dippers host nearly edge-on (70°) protoplanetary discs that allow close-in (<1 au) dust lifted slightly out of the midplane to partially occult the star. The identification of a face-on dipper disc and growing evidence of inner disc misalignments brings this scenario into question.  Thus we uniformly (re)derive the inclinations of 24 dipper discs resolved with (sub-)mm interferometry from ALMA. We find that dipper disc inclinations are consistent with an isotropic distribution over 0°−75°, above which the occurrence rate declines (likely an observational selection effect due to optically thick disc midplanes blocking their host stars).  These findings indicate that the dipper phenomenon is unrelated to the outer (>10 au) disc resolved by ALMA and that inner disc misalignments may be common during the protoplanetary phase. More than one mechanism may contribute to the dipper phenomenon, including accretion-driven warps and "broken" discs caused by inclined (sub-)stellar or planetary companions. Accepted by MNRAS http://arxiv.org/pdf/1912.01610 ALMAを用いたギャップのある円盤の観測内側のdiskと外側のdiskとミスアライメントは割とcommonいくつかのメカニズム(質量降着によるwarpやコンバニ
The Orion Protostellar Explosion and Runaway Stars Revisited:
Stellar Masses, Disk Retention, and an Outflow from BN
John Bally 1 , Adam Ginsburg 2 , Jan Forbrich 3 , and Jaime Vargas-González 3 1 Center for Astrophysics and Space Astronomy, Astrophysical and Planetary Sciences Department, University of Colorado, UCB 389 Boulder, Colorado 80309, USA; ² Department of Astronomy, University of Florida, Bryant Space Science Center, Stadium Road, Gainesville, FL 32611; ³ Centre for Astrophysics Research, School of Physics, Astron- omy and Mathematics, Hertfordshire University, College Lane, Hatfield, AL10 9AB, UK E-mail contact: john.bally@colorado.edu The proper motions of the three stars ejected from Orion's OMC1 cloud core are combined with the requirement that their center of mass is gravitationally bound to OMC1 to show that radio source I (Src I) is likely to have a mass around 15 M ⊙ consistent with recent measurements. Src I, the star with the smallest proper motion, is suspected to be either an AU-scale binary or a protostellar merger remnant produced by a dynamic interaction 〜550 years ago. Near-infrared 2.2 μm images spanning ～21 years confirm the ～55 km/s motion of 'source x' (Src x) away from the site of stellar ejection and point of origin of the explosive OMC1 protostellar outflow. The radial velocities and masses of the Becklin-Neugebauer (BN) object and Src I constrain the radial velocity of Src x to be V LSR = −28 ± 10 km/s. Several high proper-motion radio sources near BN, including Zapata 11 ([ZRK2004] 11) and a diffuse source near IRc 23, may trace a slow bipolar outflow from BN. The massive disk around Src I is likely the surviving portion of a disk that existed prior to the stellar ejection. Though highly perturbed, shocked, and re-oriented by the N-body interaction, enough time has elapsed to allow the disk to relax with its spin axis roughly orthogonal to the proper motion. Accepted by The Astrophysical Journal http://arxiv.org/pdf/2001.00899
4
ALMA OBSERVATIONS REVEAL NO PREFERRED OUTFLOW-FILAMENT AND OUTFLOW-MAGNETIC FIELD ORIENTATIONS 5 T. Baug ¹ , Ke Wang ¹ , Tie Liu ² , Mengyao Tang ³ , Qizhou Zhang ¹ , Di Li ³ , 6 , Eswaraiah Chakali ⁷ , Sheng-Yuan Liu ² A NANDMAYEE T ej 9 , P AUL F. G OLDSMITH 10 , L EONARDO B RONFMAN 11 , S HENG -L I Q IN 3 , V IKTOR L. T OTH 12 , P AK -S HING L 13 , AND KEE-TAE KIM14の向きは大質量星形成領域(IRDC)のoutflowが磁場やフィラメントの向きと相関があるかどうか調べた=>なかったTable 1 Details of targets
ASTEでHCN(4-3)の観測でblue- emission profile県の同意Distances estimated using the Kinematic Distance Calculation Tool of Wenger et al. (2018, http://www.treywenger.com/kd/) ALMA観測:黄色がdriving sourceの位置Blue/Red: CO outflowなぜ相関がないのか: HII領域が発達しており、進化した領域を見ているから- Outflowよりも恒星風からの勢いの方が強くなる-多重星の相互作用により回転の向きがランダムになるから
The Young Suns Exoplanet Survey:  Detection of a wide orbit planetary mass companion
to a solar-type Sco-Cen member A.J. Bohn 1 , M.A. Kenworthy 1 , C. Ginski 2 , C.F. Manara 3 , M.J. Pecaut 4 et al. ¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; ² Sterrenkundig Instituut Anton Pannekoek, Science Park 904, 1098 XH Amsterdam, The Netherlands; ³ European Southern Observatory, Karl- Schwarzschild-Strasse 2, 85748 Garching bei München, Germany;  4 Rockhurst University, Department of Physics, 1100 Rockhurst Road, Kansas City, MO 64110, USA E-mail contact: bohn at strw.leidenuniv.nl The Young Suns Exoplanet Survey (YSES) consists of a homogeneous sample of 70 young, solar-mass stars located in the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an average age of 15±3 Myr. We report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211-6456207) that is located at a distance of 94.6±0.3 pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with VLT/X-SHOOTER constrain the mass of the star to 1.00±0.02 M ⊙ and an age of 16.7±1.4 Myr. The companion TYC 8998-760-1 b is detected at a projected separation of 1 ? 71, which implies a projected physical separation of 162 au. Photometric measurements ranging from Y to M band provide a mass estimate of 14±3 M jup by comparison to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q = 0.013 ± 0.003 with respect to the primary. We rule out additional companions to TYC 8998-760-1 that are more massive than 12 M iup and farther than 12 au away from the host.  Future polarimetric and spectroscopic observations of this system with ground and space based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of the circumstellar environment around this 'young Sun'. Accepted by MNRAS http://arxiv.org/pdf/1912.04284 USco1621 B and USco1556 B: Two wide companions at the deuterium-burning mass limit in Upper Scorpius Patricia Chinchilla 1.2 , Víctor J.S. Béjar 1.2 , Nicolas Lodieu 1.2 , Bartosz Gauza 3.4 , Maria Rosa Zapatero Osorio 5 et al. ¹ Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain; ² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain; ³ Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 4 Janusz Gil Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland; 5 Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain E-mail contact: pcg at iac.es Our aim is to identify analogues of gas giant planets, as companions at wide separations of very young stars.  To identify these objects, we cross correlated the Visible and Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) and the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Clusters Survey (UKIDSS GCS) catalogues to search for common proper motion companions to 1195 already known members of Upper Scorpius (USco; age ～5–10 Myr, distance ～145 pc).  We present the discovery and spectroscopic characterisation of two very wide substellar companions of two early-M stars in Upper Scorpius: USco1621 B and USco1556 B. We obtained optical and near-infrared low-resolution spectroscopy of the candidates to characterise their spectral energy distribution and confirm their membership to the association.  We also acquired adaptive optics images of the primaries and secondaries to search for signs of binarity and close companions. We determined a spectral type of M8.5 in the optical for both companions, along with L0 and L0.5 in the near-infrared for USco1621 B and USco1556 B, respectively. The spectra of the two companions show evident markers of youth.  The comparison with theoretical evolutionary models gives estimated masses of 0.015±0.002 and 0.014±0.002 M ⊙ , with temperatures of 2270±90 and 2240±100 K, respectively. The physical separations between the components of both systems are 2880±20 and 3500±40 AU for USco1621 and USco1556 systems, respectively. We did not find any additional close companion in the adaptive optics images. The probability that the two secondaries are physically bound to their respective primaries, and not chance aliguments of USco members, is 86%, and the probability that none of them are physically related is 1.0%. Accepted by A&A http://arxiv.org/pdf/1912.04150 Seeds of Life in Space (SOLIS) V. Methanol and acetaldehyde in the protostellar jet- driven shocks L1157-B0 and B1 C. Codella¹.², C. Ceccarelli².¹, E. Bianchi², N. Balucani³.².¹, L. Podio¹, P. Caselli², S. Feng².6.7, B. Lefloch², A. López-Sepulcre², R. Neri 8 , S. Spezzano 4 and M. De Simone² L1157のアウトフローショック領域のIRAM-NOEMA観測(Large programの一環) -アセトアルデヒド(CH3CHO)がどのように形成されたかが知りたい複雑な有機分子の起源に迫るgas phase v.s. dust grainどちらか利点1.原始星からのエミッションを除外できる(~0.11 pc離れている)など*先行研究ではNH2CHO(ホルムアミド)はgas phaseらしいことがわかったコントア: 12CO blueshifted outflow 8 N(CH3OH): 1.3e16 cm^-2 N(CH3CHO):7e13 cm^-2他のprotostellar envelope領域(100 au以内)とオーダーで変わらないGasかgrainか切り分けできないFuture work (gas vs grainを切り分けるためには) •ショックが起こった100年以内の領域を見つける•エチルラジカル(CH3CH2)と酸素原子の観測が重要エチルラジカルは現在観測できる知られている周波数帯にない酸素(63μm)はSOFIAが可能