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中央研究院天文及天文物理研究所
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Activity > Lunch Talk

Lunch Talk (2018)

ASIAA Lunch Talk is an institute-wide event allowing ASIAA researchers from different fields to discuss astronomy in a very casual manner. The informal meeting is usually held at lunch time on every Monday. Occasionally visitors are also invited to the lunch talk to share their research and ideas with ASIAA researchers.

NEXT Lunch Talk: 2018-09-26 Wed 12:00~13:00 [R1203]
Speaker:Jian, Shou-Ting
Topic:TBD
No. Time/Place Speaker Topic (Abstract)
download PDF: dowaload talk PDF file
12018-12-17 Mon
12:00~13:00
R1203
PC Yu
[NCU]
22018-11-26 Mon
12:00~13:00
R1203
Li-Ching Huang
[NCU]
32018-10-29 Mon
12:00~13:00
R1203
Feng-Li Lin
[NTNU]
42018-10-15 Mon
12:00~13:00
R1203
Ruolan Jin
[NTHU]
52018-10-01 Mon
12:00~13:00
R1203
Jia-Yu Ou
[NCU]
Refining period of a Mira in M33 with OGLE data analysis.
Abstract

[HBS 2006] 40671 is a confirmed long period Mira found in M33.Using observed light curves from Hartmann et al (2006) data, Barsukova et al. (2011) found a period of 665 day for this Mira. In addition to Hartmann's data (2005~2006), we also collected PTF (Palomar Transient Factory) data taken from 2009 to 2016. Combining these two datasets that spanned ~10 years can be used to refine the period of this Mira. Based on the combined light curve, we found that this Mira could exhibit a long secondary variation. To aid in our investigation, we collected known Mira light curves data from the OGLE and LAMOST/ASAS database. According to the OGLE Mira, we found majority of Mira light curves are composed with a short pulsation period and a long secondary variation. We also use machine learning to classify these OGLE Mira target. Hence we also tried to look for additional features in Mira light curves using our method, and compared to the light curve of [HBS 2006]40671 to refine its pulsation period and to determine its long secondary period, hence we also tried to look for additional features using our method,and compared to the light curve of [HBS 2006]40671. Therefore, we can use those information to refine the short period and find out the long term variation. In this work, we present our latest investigation on the period refinement of this Mira.

62018-09-26 Wed
12:00~13:00
R1203
Jian, Shou-Ting
[ASIAA]
TBD
72018-09-17 Mon
12:00~13:00
R1203
Kai-Feng Chen
[NTU/ASIAA]
Large Scale Structure—As a Probe for Cosmology
Abstract

In this 101 level lunch talk, I will introduce how to combine theories on large scale structure and the Sunyaev–Zel'dovich effect to constrain standard cosmology model. I will present the state-of-the-art cosmological constrains base on the SPT-selected clusters sample and discuss some future improvements through extra mass calibraters and enlarge SPT samples. Students with general interests in (observational) cosmology are especially welcome.

82018-09-12 Wed
12:00~13:00
R1203
Jiang, Homin
[ASIAA]
Development of High Speed Serial ADC for Radio Astronomy
92018-09-10 Mon
12:00~13:00
R1203
I-Ta Hsieh
[ASIAA]
Apply Genetic Algorithm to Model Fitting for an Astronomical Object
Abstract

Genetic Algorithm is widely adopted on multi-variables optimization problem in the academia and the industry. I applied GA on our radiative simulator SPARX to find out a 1D model of density, temperature, and dust opacity profile of NGC 1333 I4A1 to fit the multi-wavelength continuum data. I will introduce the method and show the potential to apply the method on Astronomy.

102018-09-03 Mon
12:00~13:00
R1203
Yu-Hsuan Teng
[ASIAA/NTU]
Properties and Kinematics in OMC1 with N2H+ Observations
Abstract

Using the N2H+(3-2) observed with the SMA and CSO, and N2H+(1-0) observed with the NRO 45m and ALMA + IRAM 30m, we study the structure and kinematics of the Orion Molecular Cloud 1 (OMC1). Unlike other molecular lines such as HCO+ or HCN, the observations in N2H+ are less affected by the expansion or explosion originated from the Orion KL, and can trace the dense gas distribution. Using the kinematics and structure, the OMC1 region is divided into three subregions. The northern region consists of multiple filaments parallel with each other, the western region consists of radial filaments, and the southern region is the OMC1-South. These three regions have different velocities, which exhibits a velocity structure similar to a global collapse scenario. We derived the physical parameters of these regions by conducting non-LTE analysis. The high-resolution N2H+ (3-2) and (1-0) images reveal multiple filamentary structure, having a typical width of 0.02-0.03 pc. Using the non-LTE analysis, we find that the filament regions have a higher density and a lower temperature than the non-filament regions. This may be explained by the blocking of external heating sources due to the dense gas in the filaments. We also study the gas motion inside the filaments, and compare them with the core formation model.

112018-08-27 Mon
12:00~13:00
R1203
Li-Ting Hsu & Yu-Yen Chang
[ASIAA]
“ Workshop report: Are ANG special? "
122018-08-22 Wed
12:00~13:00
R1203
Chang, Yin-Chang
[ASIAA]
TAOS 2 engineer camera installation
132018-08-20 Mon
12:00~13:00
R1203
Hua-Shan Shi
[NCU]
The Seasonal Evolution of the Atmospheres of Pluto and Other Dwarf Planets
Abstract

Dwarf planets in Kuiper belt are too far for us to study in detail by telescopic observations from Earth for past several decades. After the New Horizons spacecraft’s flyby observations of the Pluto-Charon system in July 2015, we now have a better understanding of these faraway objects. Sputnik Planitia of Pluto is one of the most important discoveries of the New Horizons spacecraft at its flyby observations of the Pluto-Charon system in July 2015. Sputnik Planitia is located at the northern mid-latitude hemisphere in the antipodal position to Charon on the opposite side. It contains a large quantity of the nitrogen ice on Pluto and the content of Pluto’s atmosphere is likely controlled by the variable sublimation rate of Sputnik Planitia’s ice. In this work, we use a coupled treatment to compute the surface temperature and pressure of Sputnik Planitia on Pluto when it revolves around the sun in its eccentric orbit with special attention to the sublimation process of the nitrogen ice stored in Sputnik Planitia. In addition, we will apply this model to other Pluto-like dwarf planets in Kuiper belt which surfaces could be mainly composed of nitrogen ice. This set of model calculations allows us to explore the range of the atmospheric contents and mass loss process of the icy dwarf planets.

142018-08-13 Mon
12:00~13:00
R1203
Chien-De Lee
[NCU]
Be stars — From PTF to ZTF
Abstract

Among the stellar spectral classifications, B-type stars are the fastest rotators with a equatorial speed of approximately 100 km/s. Some of them showing hydrogen emission line, known as Be stars, can rotate even faster, up to the break-up velocity. The formation of rapid rotation were thought to be part of the evolutionary effect, however, we found the least correlation between the age of the clusters and corresponding Be fraction through Palomar Transient Factory (PTF) project. In addition to the issue of evolution, Be stars are known variable stars, but mostly they show heterogeneous semi- or non-regular variation. Here comes Zwicky Transient Facility (ZTF) with a 47 square degree field of view, so the northern sky can be surveyed with high cadence e.g., over two times a night on galactic plan. Unlike the individual Be stars monitoring, ZTF provides an opportunity window over three years which makes systemic census possible for the photometric variability investigations of Be stars in the deeper sky. Here, we also present the preliminary light curves of Be stars from the ZTF commissioning data.

152018-08-06 Mon
12:00~13:00
R1203
Thavisha Dharmawardena
[ASIAA/NCU]
Extended dust emission from nearby Asymptotic Giant Branch stars
Abstract

Asymptotic Giant Branch (AGB) stars in the Milky Way are often overlooked due to difficulties in obtaining distances. Understanding their dust emission properties and mass-loss histories leads to better comprehension of the ISM evolution in the Milky Way, in particular its dust reservoir. Most studies have determined the stellar dust mass using mid-IR emission, but a historic cold dust reservoir from a previous mass-loss phase may remain undetected in the mid-IR, requiring observations at longer wavelengths. We present results of a search for extended dust emission from a diverse sample of AGB stars within 1 kpc. This project is part of the Nearby Evolved Star Survey (NESS), which aims to determine gas and dust return from a volume limited sample of galactic evolved stars. Observations at 450​μm​ and 850​μm​ were carried out using the SCUBA-2 instrument on the JCMT and combined with Herschel PACS observations at 70​μm​ and 160​μm from the MESS survey (Groenewegen et al., 2011; Cox et al., 2012). Using azimuthally-averaged surface brightness profiles we determined extension and percentage flux of the extended component for each source at the four wavelengths. We derived extensions at the 3σ levels greater than ~40'' for majority of the sources at SCUBA-2 850​μm​. The fraction of the flux emitted from the extended region is ~40% at 850​μm​ and ~50% at PACS wavelengths. We report a clear detection of the detached shell of U Ant in both 450​μm​ and 850​μm​. This is the first time this detached shell has been detected in the sub-mm continuum. By fitting a modified black body to four-point SEDs at each radial point we derive the dust temperature, spectral index of emissivity, and column density to probe dust mass-loss history and detect changes in physical properties of dust as a function radius (hence, time). The resulting dust-to-gas ratios are consistent with canonicalvalues. The surface density profiles suggest deviation from constant mass loss in a majority of the sources.

162018-07-30 Mon
12:00~13:00
R1203
Han Cheng
[NCU]
MHD simulations on the formation of Fermi Bubbles with magnetic field
Abstract

Fermi bubbles, black hole feedback in our Galaxy, is a huge structure in our Galactic halo. One possible origin of the bubbles is repeated star captures by the supermassive black hole at the Galactic center. We model these processes as multiple energy outbursts (a.k.a. explosions) from a small volume into a layered exponential atmosphere. We study the formation of the bubbles by the MHD simulation code FLASH4. The evolution and morphology of the bubbles is compared under different initial poloidal and toroidal magnetic field configurations.

172018-07-25 Wed
12:00~13:00
R1203
Liu, Kuan-Yu
[ASIAA]
New Spare Mixer Chips for HARP
182018-07-23 Mon
12:00~13:00
R1203
Kate Pattle
[NTHU]
First measurements of the magnetic field strength in the Pillars of Creation
Abstract

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.

192018-07-18 Wed
12:00~13:00
R1203
Wei, Ta-Shun
[ASIAA]
Introduction of Supertorrefier
202018-07-09 Mon
12:00~13:00
R1203
Tsan-Ming Wang
[NCU]
INFLUENCE OF VELOCITY DISPERSIONS ON STAR FORMATION ACTIVITIES IN GALAXIES
Abstract

We investigate the influence of the random velocity of molecular gas on the star forming activities in molecular clouds. It is known that physical states of a molecular cloud, such as temperature and density, will influence the star forming activities in the cloud. Besides, it is believed that local and turbulent motions of the molecules in the cloud might provide a significant amount of pressure against gravitational collapse and might thus prevent or reduce star formation in the cloud. However, the influence of the gas motions on the star formation activities is still poorly understood. We used the Atacama Large Millimeter/submillimeter Array (ALMA) data to obtain 12CO(J=1-0) flux and velocity dispersion, combining with the 3.6 and 8 micron mid-infrared data of the Spitzer Space Telescope to probe the effects of gas motion on star formation activities for several nearby galaxies. From our results we were able to derive a modified Kennicutt-Schmidt law with velocity dispersion as an additional parameter. We found that the higher the velocity dispersion in molecular clouds, the lower the star formation activities.

212018-07-04 Wed
12:00~13:00
R1203
Yen, Sheng-Feng
[ASIAA]
Free to get the Labview Certified!
Abstract

In this talk, I will introduce the CLAD ( Certified Labview Associate Developer) and share my experiment to get the CLAD complimentary last year.

222018-07-02 Mon
12:00~13:00
R1203
Pei-Ying Hsieh
[ASIAA]
Magnetized molecular torus in the Galactic center - Paradigm of torus surrounding supermassive black hole in galaxies?
Abstract

Utilizing James Clark Maxwell Telescope (JCMT) 850 micron SCUPOL dust polarization data, we investigate the configuration of the magnetic (B) field in the circumnuclear disk (CND) of the Galactic Center (GC). The SCUPOL data show a highly improved polarization coverage and resolution compared to earlier 100 micron observations. The 850 micron data have a resolution and coverage similar to previous 350 micron polarimetry data. However, with a proper sampling on a 10" grid, we find the 850 micron data trace the morphological structures of the CND substantially better. Furthermore, because the 850 micron trace the field deeper into the material near Sgr A*, they represent the highest resolution submillimeter probe to date of the CND magnetic field. The observed B-field morphology is well described by a self-similar axisymmetric disk model where the radial infall velocity is one quarter of the rotational velocity. A detailed comparison with higher-resolution interferometric maps from the Submillimeter Array further reveals that the $B$-field aligns with the neutral gas streamers connecting to the CND. Moreover, the innermost observed $B$-field structure also appears to trace and align with the mini-spiral located inside the CND. This suggests that there is one underlying B-field structure that is connecting the CND with its streamers and the inner mini-spiral. An estimate of beta_Plasma<=1 - based on the global B-field morphology that constrains the azimuthal-to-vertical field strength ratio of around 40 combined with a measurement of the azimuthal velocity--indicates that the B-field appears dynamically significant towards the CND and also onwards to the inner mini-spiral.

232018-06-25 Mon
12:00~13:00
R1203
I-Non Chiu
[ASIAA]
X-ray Observable to Mass Scaling Relations of the SPT-selected Galaxy Clusters at 0.2 < z < 1.5 Observed with the XMM-Newton Telescope
Abstract

In this lunch talk, I will present the state-of-the-art result of the X-ray observable to mass scaling relations based on a sample of galaxy clusters selected by the South Pole Telescope out to redshift 1.5.

242018-06-13 Wed
12:00~13:00
R1203
Chou, Chueh-Yi
[ASIAA]
Commissioning of pfs metrology camera on Subaru telescope
252018-06-11 Mon
12:00~13:00
R1203
Hsi-An Pan
[ASIAA]
Molecular Gas in Interacting Galaxies
Abstract

Galaxy interactions and mergers are often accompanied by an increase in star formation rate (SFR). Since the properties of the molecular gas are essential for star formation, it is vital to establish whether, and by how much, galaxy interaction affects the molecular gas properties, and that in turn lead to the change in SFR. We investigate the influence of galaxy interactions on global molecular gas properties by studying a sample of 61 interacting galaxies, and compare their gas properties with galaxy-properties-matched control sample (isolated galaxies). We find that SFR, gas mass, and gas fraction are gradually enhanced with respect to the control sample as two galaxies approaching each other, and also enhanced from minor to major mergers. On the other hand, dependence of gas star formation efficiency on merger properties is less obvious. According to our analysis, we conclude that galaxy interaction can modify the molecular gas properties of a galaxy, although the strength of the influence is merger properties dependent. Moreover, on the galaxy-wide scale, the total gas content, but not SFE, plays a more important role in the interaction-triggered SFR.

262018-06-04 Mon
12:00~13:00
R1203
Steven Gibson
[WKU/ASIAA]
Dust SED Mapping of Cold Diffuse Clouds
272018-05-28 Mon
12:00~13:00
R1203
Nanase Harada
[ASIAA]
Connecting Galactic and extragalactic star formation - the case of astrochemistry
282018-05-16 Wed
12:00~13:00
R1203
Cheng, Jen-Chieh
[ASIAA]
TBD
292018-05-14 Mon
12:00~13:00
R1203
Ji-Jia Tang
[NTU]
The Physical Properties of an Exceptionally Blue QSO at z ∼ 6.6 and their Implication to the Early Growth of SMBH
Abstract

We explore the early growth of supermassive black holes (SMBHs) by using a near-infrared (NIR) spectrum of a recently discovered z = 6.621 QSO PSO J006+39 in three physical properties: (1) According to the standard thin disk model, the NIR (rest-frame FUV) spectrum of this QSO is dominated by the emission from the accretion disk. We found that the power-law slope of the continuum αλ of this QSO in NIR, −2.94 ± 0.03, is much bluer than the expected slope −1.5 from the standard thin disk model. We will discuss two possibilities to explain this unique slope: the black hole spin and the Comptonisation corona of the accretion disk. (2) The growth rate can be estimated by the Eddington ratio (Lbol/LEdd). We first estimated the SMBH mass by using the Mg ii line width and the rest frame luminosity L3000Å to be ∼ 108 M⊙ . Then we derived Eddington ratio Lbol/LEdd ∼ 1. (3) There are surprisingly many metal-rich QSOs found in the early universe, given the required time for metal formation. We present two probes to estimate the metallicity of this QSO. The Fe ii/Mg ii ratio is often used as an indicator for high-z QSOs because Fe metallicity requires a certain time to be enhanced by the Type-Ia supernovae. The detection of the faint He ii line in this QSO provides another path to measure the metallicity. We used N v/He ii ratio to estimate the metallicity by considering the blue FUV continuum in the photoionization calculation. We will discuss implications of these physical properties of this QSO about the growth of SMBHs in the early universe.

302018-05-07 Mon
12:00~13:00
R1203
Gabriel Torrealba
[ASIAA]
Satellites of Satellites: two dwarf galaxies brought by the LMC
312018-05-02 Wed
12:00~13:00
R1203
Ling, Hung-Hsu
[ASIAA]
Camera Construction and Imager Characterization for TAOS2
322018-04-30 Mon
12:00~13:00
R1203
Shan-Chang Lin
[NTU]
Self-consistent construction of virialized wave dark matter halos
332018-04-23 Mon
12:00~13:00
R1203
Teppei Okumura
[ASIAA]
Intrinsic alignments of emission line galaxies at z~1.4 with Subaru FMOS/FastSound survey
342018-04-18 Wed
12:00~13:00
R1203
Chang, Shu-Hao
[ASIAA]
GLT Report
352018-04-16 Mon
12:00~13:00
R1203
Kin-Wang Ng
[ASIOP]
The EDGES 21-cm absorption signal
362018-04-09 Mon
12:00~13:00
R1203
Howard Yee
[U. of Toronto]
The Quenching of Star Formation in Galaxy Clusters since z~1
Abstract

I will present an analysis of the quenching of star formation (SF) in galaxy clusters since z~1, based on a sample of 220 galaxy clusters from the SpARCS survey in the XMM-LSS and ELAIS-N1 fields, using the public data release from HSC-SSP and Sptizer SWIRE survey data in these fields. In particular, we examine the star-forming galaxy fraction (f_SF) as a function of redshift, galaxy stellar mass, and cluster-centric radius. I will also present some preliminary results on the SFR-stellar mass relation (the "main sequence") in the field and in clusters, using a combination of HSC and Spitzer SWIRE MIPS data, over the same redshift range.

372018-04-02 Mon
12:00~13:00
R1203
Ting-Hui Lee
[Western Kentucky University]
Galactic Archaeology with Planetary Nebulae
382018-03-26 Mon
12:00~13:00
R1203
Li-Hwai Lin
[ASIAA]
How to write a good ALMA proposal?
392018-03-21 Wed
12:00~13:00
R1203
Chang, Yen-Pin
[ASIAA]
Membrane Process on OMTs and Micro-lamps
402018-03-19 Mon
12:00~13:00
R1203
Jia-Wei Wang
[NTHU]
Multi-wavelength polarization observation toward the filamentary cloud IC5146
Abstract

Whether magnetic fields are important in the star formation is a fundamental question in astrophysics. The studies in past decades show that the role of magnetic fields in star formation is complicated and diverse, and that neither of the two extreme case theories (dominating or negligible magnetic fields) can fully explain the star formation activity. Hence, the detailed investigations of the role of magnetic fields in particular physical scale, density, and environments are necessary to reveal the full picture, which thus requires multi-wavelength observations to trace. In this talk, I would present our polarization observations in optical, infrared, and submillimeter wavelengths toward the filamentary clouds IC5146. I would first discuss how deep we can trace using each data set, and further show how the role of magnetic fields possibly change in different scale.

412018-03-12 Mon
12:15~13:15
R1203
Yong Tian
[NCU]
Mass Discrepancy-Acceleration Relation in Dark Matter Problem
Abstract

Mass discrepancy-acceleration relation (MDAR) is a relation in dark matter problem found in spiral galaxies. The mass ratio between observational mass divided by baryonic mass strongly related to baryonic acceleration (or observational acceleration) but unrelated to other physical quantities (ex, radius). Recently, McGaugh et al. 2016 (PRL117.201101) revealed a tight relation between observational acceleration and baryonic acceleration in 153 spiral galaxies from SPARC database which is consistent to the MDAR. It can well explain Tully-Fisher relation, deficient dark matter in ordinary elliptical galaxies, surface densities discrepancy etc. However, our work focus (Tian & Ko 2017) on elliptical galaxies in strong lensing such as Einstein rings. We found the MDAR in 57 elliptical lenses is consistent with spiral galaxies.

422018-03-07 Wed
12:10~13:00
R1203
Huang, Yen-Ru
[ASIAA]
The Progress of 1.5 THz HEB Mixer Based Receiver Cartridge Development
432018-03-05 Mon
12:15~13:15
R1203
Hsi-An Pan
[ASIAA]
Dependence of Global and Spatially-resolved SFR-M* Relations on Galaxy Properties
Abstract

The galaxy integrated star formation rate(SFR)-stellar mass(M∗) relation holds important information for understanding the star formation history and evolution of galaxies. Although the SFR-M∗ relation has been reported with a variety of different data sets, their appearance can vary significantly from one to another. In this work, we determine what controls the integrated and the spatially-resolved SFR-M* relation in both star-forming and quiescent galaxies by linking the spatially resolved SFR-M* relation with various galaxy properties such as stellar mass and bulge-to-total light ratio using MaNGA data (Mapping Nearby Galaxies at APO).

442018-02-26 Mon
12:15~13:15
R1203
Po-Sheng Ou
[NTU]
Understanding the Evolution and Environments of Supernova Remnants Through the Lx-Size Diagram
452018-02-12 Mon
12:00~13:00
R1203
Hans Zinnecker
[Deutsches SOFIA Institut (DSI), Univ. of Stuttgart]
Airborne Far-Infrared Astronomy with SOFIA
462018-02-07 Wed
12:00~13:00
R1203
Chang, Hsiao-Wen
[ASIAA]
Growth and Characterization of Epitaxial NbN Superconducting Films on SiC Substrate
472018-02-05 Mon
12:00~13:00
R1203
Tony Beasley
[NRAO]
ngVLA
482018-01-29 Mon
12:00~13:00
R1203
Yen-Ting Lin
[ASIAA]
A tale of two scaling relations
Abstract

I will talk about observational results that have puzzled me for the past 14 years, and show how the Hyper SuprimeCam Survey could help shed light on these.

492018-01-22 Mon
12:00~13:00
R1203
Li-Hsin Chen
[NTU]
Populating H2 and CO in galaxy simulation with dust evolution
502018-01-15 Mon
12:00~13:00
R1203
Hiroyuki Hirashita
[ASIAA]
New Taiwan-Russia Collaboration on Cosmic Dust
512018-01-10 Wed
12:00~13:00
R1203
Ho, Chin-Ting
[ASIAA]
Laser Tracker Ion
522018-01-08 Mon
12:00~13:00
R1203
Sung-Yung Hsiao
[ASIAA]
Recent Results from the ASIAA NanoSIMS
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