This pages lists the Seminars that were given at the EAO offices in Hilo in 2018. The EAO staff would like to thank all guest speakers and encourage new astronomers/instrument specialists to give talks when visiting.
December 3rd, 2018, 2pm (HST)
Title: Structure of a protobinary system – an asymmetric circumbinary disk and spiral arms
Tomoaki Matsumoto, Hosei University, Japan
Recent high-resolution observations have revealed the early phases of low-mass binary and multiple star formation. Several circumbinary disks exhibit asymmetry and spiral arms as their structures. We performed numerical simulations of the circumbinary disks in order to investigate the formation mechanism of these observed features. The three-dimensional models were calculated by using the so-called fixed mesh refinement to achieve the high resolution around the binary stars. We compared the results of the simulations with the ALMA observations toward the Class I protobinary L1551 NE by using synthetic observations. The comparison demonstrates that these features are an evidence of the interaction between the circumbinary disks and binary stars via the gravitational torque, which promotes gas accretion onto the circumstellar disks and binary stars.
November 27th, 2018, 2pm (HST)
Title: Constraining the Physics of Relativistic Jets with X-ray Binaries
Alex Tetarenko, EAO
Astrophysical jets are ubiquitous phenomena in our universe, linked to a wide range of objects, from young stars to black holes. These powerful, highly collimated outflows deposit significant amounts of energy and matter into the surrounding medium, affecting star formation, galaxy evolution, and even the distribution of matter in the universe. However, despite decades of research, our current knowledge of the physics that gives rise to and governs the behaviour of these jets is still extremely limited. Of all the systems that launch jets, X-ray binaries are particularly excellent testbeds, as they evolve through bright outburst phases on rapid timescales of days to months, providing a real-time view of how these jets evolve and interact with their environment. In this talk, I will detail new tools and techniques that my team and I are developing to study X-ray binary jets, including utilizing time domain analyses to connect jet variability properties to internal jet physics, and using the astrochemical properties of regions where these jets collide with their local environment to constrain jet structure and energetics. Through this work, we also demonstrate that the relatively untested mm/sub-mm frequency bands provide a unique viewpoint on these jets, and are crucial in allowing us to open up new ways to study jet phenomena across the X-ray binary population.
November 21st, 2018, 11:30am (HST)
Title: Overview of the EHT
Izumi Mizuno, East Asian Observatory, Hawaii, USA
An overview of the EHT project, collaboration, and working groups. This talk was given after the 2018 EHTC conference from November 5-9 at Radboud University in Nijmegen, Netherlands.
November 7th, 2018, 2pm (HST)
Title: Discovery of compact jet components in NGC 2023 MM1
Li-Wen Liao, Tsing Hua University, Taiwan
Outflows, a ubiquitous phenomenon in star-forming regions, show different morphology with different selected velocity. For instance, low-velocity gas traces outflow cavities and high-velocity gas traces collimated jets. Among them, high-velocity jets, which carry a lot of momentum and kinetic energy, are closely connected with the accretion process. In this talk, I will show our SMA observation on NGC 2023 MM1, a class 0 protostar with d ~ 350 pc and L ~ 7 L☉. We resolved NGC 2023 MM1 outflows into collimated jets with high-velocity CO (2-1) gas and SiO (5-4) gas with an angular resolution of 3” and a spectral resolution of 1 km/s. Assuming CO gas is optically thin and in LTE condition, we estimated several kinematic parameters of the jets, such as mass, momentum and kinetic energy.
October 15th, 2018, 11am (HST)
Title: Cosmic Fullerenes
Jan Cami, University of Western Ontario, Canada
In recent years, fullerenes have been detected in a variety of astrophysical environments – from the circumstellar carbon-rich surroundings of evolved stars to diffuse clouds, interstellar reflection nebulae and young stellar objects. Most detections involve emission through the infrared vibrational transitions of the neutral species C60 or absorption due to the cation C60+.
In this talk, I will give an overview of the environments where we have detected fullerenes. I will summarize the key observational properties as well as what we have learned from these detections. More importantly, I will highlight some of the remaining issues we face in understanding these observations and coming up with a coherent picture for the life cycle of fullerenes and related carbonaceous species in space.
September 20th, 2018, 2pm (HST)
Title: Unveiling the Complex Organic Molecules and Infalling Envelope of the Class 0 Protostar BHR 71
Yao-Lun Yan, University of Texas at Austin, U. S. A.
Star formation processes such as infall, accretion, and outflows increase the complexity of molecules, allowing us to use those molecules to probe the physical environments where stars form. The most deeply embedded protostars present particularly rich spectra of molecules due to their dense envelope and active infall and outflows, making them best probed by molecular spectroscopy. Stars form via the infall of mass from a core, but direct evidence for such infall has been elusive. The most direct probe of infall is redshifted absorption against the central continuum source, which is best shown in dense gas tracers, such as HCO+ and HCN. Our ALMA observations of these two molecules show such redshifted absorption toward an isolated core, BHR71. Both lines show a similar redshifted absorption profile. We model the line profiles with 1D and 3D radiative transfer calculations to further constrain the physical properties of the collapsing envelope. We also found emissions of complex organic molecules around 345 GHz. BHR71 shows a similar suite of lines compared to another isolated core, B335, which only has 10% of the luminosity of BHR71 but is at a similar evolutionary stage. We found that complex organic molecules emit from a compact region centered on the continuum source, which is barely resolved with a beam of 0.27″, corresponding to ~50 AU. Several COMs, such as methanol and methyl formate, show clear signatures of rotation, which is consistent with the model of rotating infalling envelope. We investigate the physical environment in the inner 50 AU via emission of complex organic molecules; combined with the redshifted absorption we can follow material from the envelope to the central protostar.
September 12th, 2018, 2pm (HST)
Title: The TOP-SCOPE survey of Planck Galactic Cold Clumps
Tie Liu, KASI, South Korea
Stars form in dense regions within molecular clouds, called pre-stellar cores (PSCs), which provide information on the initial conditions in the process of star formation. The low dust temperature (< 14 K) of Planck Galactic Cold Clumps (PGCCs) makes them likely to be pre-stellar objects or at the very initial stage of protostellar collapse. “TOP-SCOPE” are joint survey programs targeting at Planck Cold Clumps. “TOP”, standing for “TRAO Observations of Planck cold clumps”, aims at an unbiased CO / 13CO survey of 2000 Planck Galactic Cold Clumps with the Taeduk Radio Astronomy Observatory 14-meter telescope. “SCOPE”, standing for “SCUBA-2 Continuum Observations of Pre-protostellar Evolution”, is a legacy survey using SCUBA-2 on the James Clerk Maxwell Telescope (JCMT) at the East Asian Observatory (EAO) to survey 1000 Planck Galactic Cold Clumps at 850 μm. We are also actively developing follow-up observations with other ground-based telescopes (NRO 45-m, Effelsberg 100-m, IRAM 30-m. SMT, KVN, SMA, ALMA). We aim to statistically study the initial conditions of star formation and cloud evolution in various kinds of environments. I will present the progress and the future plans of this internationally-collaborating project.
August 27th, 2018, 2pm (HST)
Title: First Measurements of the Magnetic Field Strength in the Pillars of Creation
Kate Pattle, National Tsing Hua University, Taiwan
In this talk, I will present the first high-resolution, submillimetre-wavelength, polarimetric observations of – and thus direct observations of the magnetic field morphology within – the dense gas of the Pillars of Creation in M16. These recent results from the JCMT BISTRO (B-fields in Star-forming Region Observations) survey show that the magnetic field runs along the length of these photo-ionized columns, perpendicular to, and decoupled from, the field in the surrounding photoionized cloud. I will discuss estimation of the magnetic field strength in the columns, and its implications for the formation of the Pillars. I will further discuss the energy balance in the Pillars, and hypothesize on the effect of the magnetic field on the future evolution and lifetime of the Pillars.
August 7th, 2018, 9am (HST)
Title: Temperature Sensors [Tracking Temperature Changes Across the JCMT Dish on ~10 minute timescales]
Mailani Neal, EAO/JCMT Summer Intern
July 11th, 2018, 2pm (HST)
Title: Two Years of Monsters in the Dark: My WISDOM So Far
Eve North, Cardiff University, UK
For my PhD I have been working as part of a survey of supermassive black hole masses in the local universe (WISDOM). I will take you through our novel mass measurement technique where we use molecular gas as a tracer of the central velocity field of a galaxy. I will also give a quick overview of what I was observing at the JCMT.
May 18th, 2018, 2pm (HST)
Title: The Liverpool Telescope and the New Robotic Telescope
Helen Jermak, Liverpool John Moores University, UK
The Liverpool Telescope is a 2-metre, fully robotic and autonomous telescope situated on Roque de los Muchachos, La Palma. Operating robotically since 2004, it has seen great success in the area of transient and time domain astronomy, along with long term monitoring campaigns. I will present the telescope and its instrumentation suite, which currently consists of 6 instruments co-mounted on the Cassegrain, and one fibre-fed in the observatory. I will showcase some of the science made possible using the Liverpool Telescope and highlight our successful outreach projects with the National Schools’ Observatory.
I will also introduce the New Robotic Telescope, which will be a 4-metre rapid response telescope designed for even faster follow-up of transient objects, co-located on La Palma and used in synergy with a newly refurbished Liverpool Telescope.
May 1st, 2018, 2pm (HST)
Title: Astrochemistry Tools: From Star Formation to the Cradle of Life
Siyi Feng, EACOA fellow, NAOJ/NAOC/ASIAA
Thanks to the performance of the state-of-the-art radio telescopes, increasing detections of molecular species in the ISM improves our knowledge of the Universe. How are the formation and destruction processes of these interstellar molecules? What can these detections tell us about the star and planet formation? What is the link between the complex organics in the ISM and the seed of our lives? These fundamental questions are still unclear.
In this talk, I will start with presenting my chemical studies towards a series of high-mass star-forming regions (HMSFRs), where the intensive dynamics drive complex chemistry, bringing in prebiotic species. From the observations of the HMSFRs spanning all evolutionary stages at mm wavelengths, I will show that how the molecular lines play the role of (1) characterizing these chemically complicated regions and (2) diagnosing the evolutionary status of the kinematically complicated regions.
Later, I will also introduce some large observational projects I am currently leading towards the initial stage of both high-mass and low-mass star-forming regions. The preliminary results of these projects reveal the capability of astrochemical tool in (1) studying the high-mass and low-mass star formation on a global scale and (2) understanding the missing link from the star-forming region to the planetary system.
April 24th, 2018, 2pm (HST)
Title: Beyond the Event Horizon Telescope: the Event Horizon Imager
Remo Tilanus, Leiden Observatory & Radboud University, The Netherlands
After a brief introduction and status update of current observations to image supermassive black holes by the Event Horizon Telescope, I will introduce the Event Horizon Imager (EHI): a novel concept to obtain high-frequency (e.g. 690 GHz) and high-resolution VLBI images of black holes using two small space-based dishes orbiting the Earth. The two dishes will act as an stand-alone interferometer with on-board correlation and, when put into slightly different orbits effectively, create a continuous zoom lens over the timescales of one or a few months. The dense and long-term sampling will result in high-fidelity time-averaged images of nearby supermassive black holes and this relative simple approach to a space-based interferometer array keeps it within the envelope of a medium-sized mission. The VLBI group at Radboud University leads a conceptual design study to e.g. address the challenge tracking of the phase centers of each satellite with sub-mm accuracy.
April 10th, 2018, 2pm (HST)
Lapo Fanciullo, ASIAA, Taiwan
The study of cosmic dust often involves interpreting observations using dust models, for which a central parameter is the dust far-infrared opacity κ. However, we are learning from both astronomical observations and laboratory tests on dust analogues that our models of dust opacity — one of the most popular being a power law, κ ∝ λ–β (usually with β ~ 2) — are too simplistic. Two facts in particular emerge:
- For most candidate dust materials the opacity κ(λ) does not follow a power law: its slope decreases beyond a certain wavelength (typically 400–700 μm);
- The optical properties of materials often depend on temperature as well; for instance opacity often increases with T.
We are working on the laboratory-measured opacities of several candidate dust materials to parametrize them as functions of λ and T. This parametrization will be the first step in building a more physically realistic and flexible dust model, which will allow to find potential systematics in previous fit results.
March 21st, 2018, 2pm (HST)
Title: Study of X-ray Brown Dwarfs Associated with Molecular Clouds in Young Star Cluster IC 348
Bhavana Lalchand, National Central University, Taiwan
Brown dwarfs have masses (15 – 80 MJup) below that required to maintain core hydrogen fusion. Such a substellar population in star-forming regions is the critical first step to understand their formation mechanism (do they form like stars, or like planets?). The sample also serves to bridge the knowledge of free-floating planets versus exoplanets. We have identified brown dwarf candidates via imaging detection of possible water absorption, one of the characteristics of cool atmospheres, in the young (3-Myr) star cluster IC 348. Some of these are matched with X-ray sources and also with JCMT 850-μm emissions, thus are magnetically active brown dwarfs in their infancy. These embedded X-ray brown dwarfs have Lx/Lbol, to be compared with other young stellar populations such as for typical T Tauri stars, and for Herbig Ae/Be stars, or with for OB stars. While late-M dwarfs are expected to be fully convective, as is the case in dMe stars, to be X-ray emitters, even cooler L and T type brown dwarfs and planet-mass objects may have largely neutral atmospheres, hence unlikely to activate magnetic dynamos. Our brown dwarf sample is the most comprehensive a young star cluster, and we present their spectral typing, X-ray and submillimeter properties.
March 12th, 2018, 2pm (HST)
Doug Johnstone, NRC-Canada Herzberg Astronomy and Astrophysics
We have undertaken a 3-year dedicated JCMT/SCUBA-2 monitoring program of eight nearby star-forming regions (Herczeg et al. 2017) to search for sub-mm brightness variations as a proxy of episodic accretion. In this talk I will discuss the novel methods used to reach a relative calibration of 2% (Mairs et al. 2017a). I will then present the first variable source found in the sub-mm with a periodic light curve, the Class I protostar EC 53 in Serpens Main (Yoo et al. 2017). The change in sub-mm brightness of EC 53 is interpreted as dust heating in the envelope, generated by a luminosity increase of the protostar. The sub-mm lightcurve resembles the historical K-band light curve, which varies by a factor of ∼6 with a 543 period and is interpreted as accretion variability excited by interactions between the accretion disk and a close companion.
I will also discuss the results from a comparison between archival SCUBA-2 observations and the first year of our dedicated survey (Mairs et al. 2017b) and perform a statistical analysis of the first eighteen months of the survey (Johnstone et al. 2018). From these studies, we conclude that greater than 5% of the known deeply embedded protostars are found to vary in the sub-mm. I will close by contemplating the bright future for both observations and theoretical investigations of sub-mm variability from deeply embedded protostars.
February 9th, 2018, 2pm (HST)
Title: Molecular-cloud-scale chemical composition in low-metallicity dwarf galaxies
Yuri Nishimura, University of Tokyo, Japan
In the Local Group, there are several tens of dwarf galaxies, which have sub-solar metallicity. They provide us a great opportunity to constitute a basic template to study faint low-metallicity galaxies, such as those at high redshift. Because metallicity is an important parameter which significantly affects gas-phase and grain surface chemistry, chemical compositions of molecular clouds in low-metallicity galaxies are of great interest. To investigate the chemical composition in low-metallicity environments, we have conducted spectral line survey observation in the 3 mm band (85 – 116 GHz) toward low-metallicity dwarf galaxies, the Large Magellanic Cloud, IC10, and NGC 6822. The lines of CCH, HCN, HCO+, HNC, CS, SO, 13CO, and 12CO have been detected. The spectral intensity patterns are found to be similar among three dwarf galaxies. Compared with solar-metallicity environments, the chemical compositions of dwarf galaxies are characterized by deficient nitrogen-bearing molecules, as a direct effect of the lower elemental abundance of nitrogen, and abundant CCH and deficient CH3OH, as an effect of extended photon dominated regions in cloud peripheries due to the lower abundance of dust grains.
February 5th, 2018, 2pm (HST)
Title: A Case Study of Triggered Star Formation in Cygnus X
Soumen Deb, University of Alberta, Canada
Cygnus X is among the most active star-forming regions in our galaxy. We observe a structure in the form of a comet in the neighborhood of Cygnus OB2. Using JCMT, DRAO and HERSCHEL observational data, we analyze the gas structure and molecular properties of the region. Molecular lines reveal the presence of outflows, which in turn, affirm active star formation in the cometary structure. This is a work in progress. We are looking into the possible source(s) of ionization that might have caused the observed cometary shape and the star formation within it.