午餐會報 (2016)

The small icy bodies beyond Neptune in the Kuiper belt originated in the construction zones that formed our planets. These bodies inform our knowledge about the growth of planetary embryos and the evolution of our Solar System. We have an understanding of the surface properties for the largest Kuiper belt objects (KBOs) which retain their primordial inventory of volatile ices. Yet for the smaller typical > 22 mag KBO where we have previously had to rely on what colors and light curves reveal by proxy, this picture remains incomplete. Most KBO physical property studies examine the hodgepodge set of KBOs discovered by surveys with different and varying detection biases that make it challenging to test giant planet migration hypotheses and formation theories for the Solar System’s planetesimal disk. The Outer Solar System Origins Survey (OSSOS) is an on-going large program on the Canada-France-Hawaii Telescope (CFHT) which for the first time provides a large enough sample of KBOs (~500) to study in a survey where all the detection biases are well characterized. Colours of the Outer Solar System Origins Survey (Col-OSSOS), is a companion 3-year (386-hour) guaranteed time Large Program on 8-m Gemini North telescope to measure a single epoch of g,r,and J band for a sample of OSSOS discovered KBOs with m_r’ <= 23.5 mag. Col-OSSOS will create an unprecedented dataset combining surface color information, orbital dynamics, and population statistics to probe the origin and history of the Kuiper belt. Started in August 2014, the first full year and a half of data collection for Col-OSSOS is complete and the analysis work is in progress. I will present a brief overview of Col-OSSOS and an update of where the project is today.

Although, the main design of SMA receiver have been done in 20 years ago. But, IAA still updated and maintained the SMA receiver. In this take, we will talk the SMA receiver, and what we did in past 3 years. It including, the manufacture/ procure new component (mixer, feed-horn, LO system)。 And final test of receiver and the problem we got.

The long-term evolution of objects in the outer n:1 resonances with Neptune provide clues to the evolutionary history of the Solar System. Based on 4 objects with semi-major axes near the 5:1 Neptune resonance, we estimate a substantial and previously unrecognized population of objects, perhaps more significant than the population in the 3:2 (Plutino) resonance. Understanding the characteristics and trapping history for objects in these populations is critical for constraining the dynamical history of the solar system. The 4 objects detected in the Canada-France Ecliptic Plane Survey (CFEPS) were classified using dynamical integrations. Three are resonant, and the fourth appears to be a resonance diffusion object, part of a population which exited the resonance through chaotic diffusion. The dynamical behavior of the known objects, suggests that the trapping mechanism for the 5:1 resonance is resonance sticking from the scattering objects. However, our investigations of Solar System evolution models show that they do not emplace a sufficiently large population into this resonance, and the source of this large population remains unexplained.

To date, over 5,000 exoplanets and planet candidates have been discovered. From the exotic exo-Neptunes to potentially habitable Earth-like planets, I will describe two methods to model the atmospheres of these planets. First, I will present a prescription of using the state-of-the-art stellar evolution code Modules for Experimental Astrophysics (MESA) to model the thermal evolution of sub-Neptune sized planets having hydrogen-helium envelopes. I will also describe an updated version of the Kasting climate model and using it to calculate the upper atmospheric conditions for planets warmer than the present Earth. I will also go over the results of using these models to generate a sample planet population as well as predicting the temperatures and water concentrations in the stratospheres of terrestrial planets. Finally, I will briefly illustrate how numerical models such as these could assist in the characterization efforts of exoplanets in future missions and observational surveys.

I will report on what I heard in the US Radio/millimeter/submillimeter Science Futures II Conference, held at Baltimore on August 3-5. This was a meeting for astronomers to brainstorm what to do in the future.

In order to understand the formation of the multipolar structures of the pre-planetary nebula CRL 618, we perform 3D simulations using a multidirectional bullet model. The optical lobes of CRL 618 and fast molecular outflows at the tips of the lobes have been found to have similar expansion ages of ˜100 yr. Additional fast molecular outflows were found near the source along the outflow axes with ages of ˜45 yr, suggesting a second episode of bullet ejections. Thus, in our simulations, two episodes of bullet ejections are assumed. The shaping process is simulated using the ZEUS-3D hydrodynamics code that includes molecular and atomic cooling. In addition, molecular chemistry is also included to calculate the CO intensity maps. Our results show the following: (1) Multiepoch bullets interacting with the toroidal dense core can produce the collimated multiple lobes as seen in CRL 618. The total mass of the bullets is ˜0.034 M_⊙ , consistent with the observed high-velocity (HV) CO emission in fast molecular outflows. (2) The simulated CO J = 3-2 intensity maps show that the low-velocity cavity wall and the HV outflows along the lobes are reasonably consistent with the observations. The position-velocity diagram of the outflows along the outflow axes shows a linear increase of velocity with distance, similar to the observations. The ejections of these bullets could be due to magnetorotational explosions or nova-like explosions around a binary companion.

http://www.cvent.com/events/half-a-decade-of-alma-cosmic-dawns-transformed/event-summary-12c52aba230240578621efced142116e.aspx

Most stars form in binary or multiple systems, but how such stars come into birth is poorly understood. This is particularly true for high-mass stars. It is very difficult to directly image high-mass binaries or multiples in formation, because they are distant, deeply embedded, and in a clustered and complex environment. Observations of parsec sized outflows or jets could be a useful probe to the central multiplicity, and the morphological and kinematical structures of the outflows may provide valuable insights into the formation mechanism of the central binaries or multiples. Here I shall talk about our high resolution observations of collimated and precessing outflows in a high-mass star forming core, and discuss about how these observations help us to understand the formation of the central proto-binary or triple star.

How the mass accretion rate of SuperMassive Black Holes (SMBHs) is related to the gas feeding from the larger spatial scales, and how it is related to the energetic jet/outflow activities, are fundamental questions for the understandings of the active galactic nuclei (AGN). Faraday Rotation Measure (RM), the tracer of electron column density and magnetic field strength along the line of sight, is one of the powerful method to constrain the mass accretion rate at the vicinity of SMBH. We present the polarimetric results on the core emissions of Cygnus A utilizing Sub Millimeter Array (SMA) at millimeter wavelengths and derive the constraints on the Faraday rotation measure. There is no statistically significant detection (less than 0.9% as 3 sigma) of the polarized emissions from Cygnus A. Low fractional polarization at 230 GHz is presumably due to variating Faraday RM screen since the high percentage of polarization (12 %) have been detected with mid-Infrared observations. With the scenarios of beam depolarizations from the accretion flow, the mass accretion rate and the accretion power can be constrained, and convection-dominated accretion flow solution can be ruled out.

We have realized epitaxial 4.7 nm- NbN film on a (100)-oriented 3C-SiC/Si substrate by dc reactive magnetron sputtering at high temperature. This is further confirmed by high-resolution transmission electron microscopy (HRTEM). We present the first report of 1.3 nm shows a superconducting transition temperature of 8.8K, which is the highest reported for NbN films of comparable thickness. For comparison, the NbN films with a thickness between 1.3 and 6 nm were deposited, and the relationship between resistivity and superconducting properties of the differently thick NbN films are discussed. In addition, the aging effects of 2.6 nm-NbN film are also studied.

While I stayed in Marseille in November, I learned how to use an spectral (SED) fitting code, Cigale. I will briefly talk about it and introduce our plan of an application to Lyman break galaxies at high redshift.