Measuring the Distribution and Excitation of Cometary CH3OH Using ALMA
M. A. Cordiner, S. B. Charnley, M. J. Mumma, D. Bockelée-Morvan, N. Biver, G. Villanueva, L. Paganini, S. N. Milam, A. J. Remijan, D. C. Lis, J. Crovisier, J. B… 展开作者
M. A. Cordiner, S. B. Charnley, M. J. Mumma, D. Bockelée-Morvan, N. Biver, G. Villanueva, L. Paganini, S. N. Milam, A. J. Remijan, D. C. Lis, J. Crovisier, J. Boissier, Y. -J. Kuan, I. M. Coulson
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Submitted to Astronomy in Focus, Volume 1. Based on work presented at the XXIXth IAU General Assembly, August 2015
The Atacama Large Millimeter/submillimeter Array (ALMA) was used to obtain measurements of spatially and spectrally resolved CH$_3$OH emission from comet C/2012 K1 (PanSTARRS) on 28-29 June 2014. Detection of 12-14 emission lines of CH$_3$OH on each day permitted the derivation of spatially-resolved rotational temperature profiles (averaged along the line of sight), for the innermost 5000 km of the coma. On each day, the CH$_3$OH distribution was centrally peaked and approximately consistent with spherically symmetric, uniform outflow. The azimuthally-averaged CH$_3$OH rotational temperature ($T_{rot}$) as a function of sky-projected nucleocentric distance ($ρ$), fell by about 40 K between $ρ=0$ and 2500 km on 28 June, whereas on 29 June, $T_{rot}$ fell by about 50 K between $ρ=$0 km and 1500 km. A remarkable ($\sim50$ K) rise in $T_{rot}$ at $ρ=$1500-2500 km on 29 June was not present on 28 June. The observed variations in CH$_3$OH rotational temperature are interpreted primarily as a result of variations in the coma kinetic temperature due to adiabatic cooling, and heating through Solar irradiation, but collisional and radiative non-LTE excitation processes also play a role.
Low mass stars might offer today the best opportunities to detect and characterise planetary systems, especially those harbouring close-in low mass temperate planets. Among those stars, TRAPPIST-1 is exceptional since it has seven Earth-sized planets, of which three could sustain liquid water on their surfaces. Here we present new and deep ALMA observations of TRAPPIST-1 to look for an exo-Kuiper belt which can provide clues about the formation and architecture of this system. Our observations at 0.88 mm did not detect dust emission, but can place an upper limit of 23$μ$Jy if the belt is small…
We report the first survey of molecular emission from cometary volatiles using standalone Atacama Compact Array (ACA) observations of the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2015 ER61 (PanSTARRS) carried out on UT 2017 April 11 and 15, shortly after its April 4 outburst. These measurements of HCN, CS, CH$_3$OH, H$_2$CO, and HNC (along with continuum emission from dust) probed the inner coma of C/2015 ER61, revealing asymmetric outgassing and discerning parent from daughter/distributed source species. This work presents spectrally integrated flux maps, autocorrela…
Observations of the sungrazing comet C/2012 S1 (ISON) were carried out using the Atacama Large Millimeter/submillimeter Array (ALMA) at a heliocentric distance of 0.58-0.54 AU (pre-perihelion) on 2013 November 16-17. Temporally resolved measurements of the coma distributions of HNC, CH$_3$OH, H$_2$CO and dust were obtained over the course of about an hour on each day. During the period UT 10:10-11:00 on Nov. 16, the comet displayed a remarkable drop in activity, manifested as a $>42$% decline in the molecular line and continuum fluxes. The H$_2$CO observations are consistent with an abrupt, $\…
A Multi-Wavelength Study of Comet C/2022 E3 (ZTF): Complementary ALMA and JWST Investigations of Water and Methanol in Cometary Comae
University of Virginia（弗吉尼亚大学）；NASA Goddard Space Flight Center（NASA戈达德太空飞行中心）；Catholic University of America（美利坚天主教大学）；American University（美国大学）；National Radio Astronomy Observatory（国家射电天文台）；Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université（巴黎天文台、巴黎文理研究大学、法国国家科学研究中心、索邦大学、巴黎西岱大学、CY塞尔吉-蓬图瓦兹大学）；Institut de Radioastronomie Millimetrique（毫米波射电天文学研究所）
本研究利用JWST和ALMA对彗星C/2022 E3 (ZTF)的多波段观测，分析了水和甲醇的分布及旋转温度变化，揭示了彗核 coma 中的化学特征与热力学过程。
The optical properties of the second generation dust that we observe in debris disks remain quite elusive, whether it is the absorption efficiencies at millimeter wavelengths or the (un)polarized phase function at near-infrared wavelengths. Thankfully the same particles are experiencing forces that are size dependent (e.g., radiation pressure), and with high angular resolution observations we can take advantage of this natural spatial segregation. Observations at different wavelengths probe different ranges of sizes, and there is therefore a great synergy in multi-wavelength observations to be…
New 12C/13C and 14N/15N isotopic ratio measurements in Jupiter's stratosphere revealed by ALMA
Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS（波尔多天体物理学实验室，波尔多大学，法国国家科学研究中心）；LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎天文台 LIRA 实验室，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎西岱大学）；Max-Planck-Institute for Solar System Research, Göttingen（马克斯·普朗克太阳系研究所）
We present a CO(2-1) and 1240 um continuum survey of 23 debris disks with spectral types B9-G1, observed at an angular resolution of 0.5-1 arcsec with the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was selected for large infrared excess and age ~10 Myr, to characterize the prevalence of molecular gas emission in young debris disks. We identify three CO-rich debris disks, plus two additional tentative (3-sigma) CO detections. Twenty disks were detected in the continuum at the >3-sigma level. For the 12 disks in the sample that are spatially resolved by our observations, we …
We present a spatially resolved map of integrated-intensity and abundance of Neptune's stratospheric hydrogen cyanide (HCN). The analyzed data were obtained from the archived 2016 observation of the Atacama Large Millimeter/submillimeter Array. A 0.42 $\times$ 0.39 arcseconds synthesized beam, which is equivalent to a latitudinal resolution of $\sim$20 degrees at the disk center, was fine enough to resolve Neptune's 2.24 arcseconds diameter disk. After correcting the effect of different optical path lengths, a spatial distribution of HCN emissions is derived over Neptune's disk, and it clearly…
Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially-resolved distributions of HCN, HNC, H$_2$CO and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution $\approx0.5''$), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distri…
Accurate disk mass measurements are necessary to constrain disk evolution and the timescale of planet formation, but such measurements are difficult to make and are very dependent on assumptions. Here we look at the assumption that the disk is optically thin at radio wavelengths and the effect of this assumption on measurements of disk dust mass. We model the optical to radio spectral energy distributions (SEDs) of 41 protoplanetary disks located in the young (~1-3 Myr old) Lupus star-forming region, including 0.89 mm, 1.33 mm, and 3 mm flux densities when available. We measure disk dust masse…
The proposed CUBES spectrograph for ESO's Very Large Telescope will be an exceptionally powerful instrument for the study of comets. The gas coma of a comet contains a large number of emission features in the near-UV range covered by CUBES (305-400 nm), which are diagnostic of the composition of the ices in its nucleus and the chemistry in the coma. Production rates and relative ratios between different species reveal how much ice is present and inform models of the conditions in the early solar system. In particular, CUBES will lead to advances in detection of water from very faint comets, re…
The Evolution in Coma Molecular Composition of Comet C/2017 K2 (PanSTARRS) Across the H$_2$O Sublimation Zone: ALMA Imaging of an H$_2$O-Dominated Coma
NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；American University（美国大学）；The Catholic University of America（美利坚天主教大学）；National Radio Astronomy Observatory（美国国家射电天文台）；Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎天文台、巴黎文理研究大学、法国国家科学研究中心、索邦大学、巴黎西岱大学）
Turbulence is a crucial factor in many models of planet formation, but it has only been directly constrained among a small number of planet forming disks. Building on the upper limits on turbulence placed in disks around HD 163296 and TW Hya, we present ALMA CO J=2-1 line observations at $\sim0.3"$ (20-50 au) resolution and 80 ms$^{-1}$ channel spacing of the disks around DM Tau, MWC 480, and V4046 Sgr. Using parametric models of disk structure, we robustly detect non-thermal gas motions around DM Tau of between 0.25 c$_s$ and 0.33 c$_s$, with the range dominated by systematic effects, making …
Cometary studies suggest that the organic composition of the early Solar Nebula was rich in complex nitrile species such a CH$_3$CN. Recent ALMA detections in protoplanetary disks suggest that these species may be common during planet and comet formation, but connecting gas phase measurements to cometary abundances first requires constraints on formation chemistry and distributions of these species. We present here the detection of seven spatially resolved transitions of CH$_3$CN in the protoplanetary disk around the T-Tauri star TW Hya. Using a rotational diagram analysis we find a disk-avera…
Small organic molecules, such as C2H, HCN, and H2CO, are tracers of the C, N, and O budget in protoplanetary disks. We present high angular resolution (10-50 au) observations of C2H, HCN, and H2CO lines in five protoplanetary disks from the Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program. We derive column density and excitation temperature profiles for HCN and C2H, and find that the HCN emission arises in a temperate (20-30 K) layer in the disk, while C2H is present in relatively warmer (20-60 K) layers. In the case of HD 163296, we find a decrease in column density for …
The spectrum of stars in the submillimeter to centimeter wavelength range remains poorly constrained due to a lack of data for most spectral types. An accurate characterization of stellar emission in this regime is needed to test stellar atmosphere models, and is also essential for revealing emission associated with unresolved circumstellar debris. We present ALMA observations of the three nearby, main-sequence, debris-poor, F-type stars $γ$ Lep, $γ$ Vir A, and $γ$ Vir B at 0.87 and 1.29 millimeters. We use these data to constrain semi-empirical atmospheric models. We discuss the atmospheric s…
During the million years of evolution, gas dust and ice in protoplanetary disks can be chemically reprocessed. There are evidences that the gas-phase carbon and oxygen abundances are sub-solar in disks belonging to nearby star forming regions. These findings have a major impact on the composition of the primary atmosphere of giant planets (but it may also be valid for super-Earths and sub-Neptunes) as they accrete their gaseous envelopes from the surrounding material in the disk. In this study, we performed a thermo-chemical modelling analysis with the aim at testing how reliable and robust ar…
We perform a comprehensive demographic study of the CO extent relative to dust of the disk population in the Lupus clouds, in order to find indications of dust evolution and possible correlations with other properties. We increase up to 42 the number of disks of the region with measured CO and dust sizes ($R_{\mathrm{CO}}$, $R_{\mathrm{dust}}$) from observations with the Atacama Large Millimeter/submillimeter Array (ALMA). The sizes are obtained from modeling the ${^{12}}$CO $J = 2-1$ line emission and continuum emission at $\sim 0.89$ mm with an empirical function (Nuker profile or Gaussian f…
