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2012-05

Surveys for Lyman Alpha Blobs at z=2 and 3 / Infrared Linear and Circular Polarimetry of the NGC 6334 Star Forming Region

[Speaker 1]
Takatoshi Shibuya
[Title]
Surveys for Lyman Alpha Blobs at z=2 and 3
[Abstract]
LyA blobs (LABs) are mysterious extended sources at z ~ 2-6. Because LABs are thought to closely relate to the formation of / the feedback from massive galaxies, investigating the origin of their brightness and spatial extent is quite important. However, despite intensive observational and theoretical approaches, the formation mechanisms of LABs have been poorly constrained. In order to understand their hidden total energy budget and relationship with other galaxy populations, such as compact Lyman Alpha Emitters (LAEs) or massive Sub-Millimeter Galaxies (SMGs) selected by using various wavebands, surveys for LABs in well-observed fields in multi-wavelengths are crucially required.
For this purpose, we have undertaken narrow-band imaging surveys in 2 MUSYC fields, the Extended Chandra Deep Field-South and the Extended Hubble Deep field-South, for LABs at z=2.1 and 3.1. In this presentation, I will provide our preliminary results.
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[Speaker 2]
Jungmi Kwon
[Title]
Infrared Linear and Circular Polarimetry of the NGC 6334 Star Forming Region
[Abstract]
Magnetic fields have been thought to play a crucial role in regulating accretion onto protostars, both in powering and shaping outflows and removing angular momentum from disk material, to allow the protostar to gain mass. However, the precise role of the magnetic field is poorly understood and evidence for its shape and structure has not been forthcoming. Getting evidence for the morphology of these fields has been tricky though – and this is an area in which polarimetry can help. In particular, circular polarization can provide evidence for changing grain/field alignment directions along the line-of-sight and hence the presence of twisting fields. However, the observational database of circular polarimetry in star forming regions is still very small. In this presentation, we present deep linear and circular polarization images of the NGC 6334 massive star-formation complex observed in the near-infrared bands.

Preliminary study on the characteristics of polar faculae / Searching for Planetary Mass Objects in Taurus Molecular Cloud

[Speaker 1]
John K Anjali
[Title]
Preliminary study on the characteristics of polar faculae
[Abstract]
TBA
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[Speaker 2]
Takuya Suenaga
[Title]
Searching for Planetary Mass Objects in Taurus Molecular Cloud
[Abstract]
A large number of substellar-mass objects isolated in star forming regions are now known, with masses ranging from those of brown dwarfs (BDs) to Planetary Mass Objects (PMOs). However, it is not well known the frequency of these objects or how they are formed. We have conducted deep i’, z’ observations toward the Taurus molecular cloud.
Based on the color selection, we have first found PMO candidates in Taurus. After planning spectroscopic follow-up, if these are confirmed to be YSOs and low effective temperature, we can suggest that the Initial Mass Function in Taurus continues into the planetary mass.

Settling Process of Dust Aggregates in Protoplanetary disks with Porosity Evolution

【日時】5月16日(水) 10:30~12:00
【場所】国立天文台・三鷹 中央棟(北)1階 講義室
【発表者1(敬称略)】片岡章雅(総研大 D1・三鷹、指導教員 : 富阪幸治)
【タイトル】
Settling Process of Dust Aggregates in Protoplanetary disks with Porosity Evolution
アブストラクト
abstract: How micron-sized dust aggregates evolve to kilo-meter-sized planetesimals in protoplanetary disks is one of the most important problems of the planet formation. Some previous studies using BPCA and/or BCCA models have shown that porosity has strong effects on coagulation and settling of dust aggregates. However, effects of the porosity evolution have not been taken into account before. We simulate coagulation of dust aggregates settling to an equatorial plane in a protoplanetary disk, using QBCCA model, in which the porosity evolution depends on the volume ratio of colliding two aggregates. We show that porous aggregates grow slowly and settle in longer timescale compared to compact grains. We also calculate wavelength-dependent optical depth and find that the 10 $\micron$ silicate feature remains in the case of porous aggregates even after they grow in the disk. Moreover, we find that compaction of dust aggregates affects optical depth in (sub)mm wavelength, which would be detected by ALMA.

Search for high-redshift protoclusters by wide-field imaging / Molecular gas and star formation properties of NGC 628

【日時】5月2日(水) 10:30~12:00
【場所】国立天文台・三鷹 中央棟(北)1階 講義室
【発表者1】利川潤 (総研大 D1、指導教員:柏川伸成)
【タイトル】Search for high-redshift protoclusters by wide-field imaging
【Abstract】
Galaxy clusters play an important role for the large-scale structure of the universe and galaxy evolution. Galaxy clusters are located in the densest peaks of dark matter, and galaxies lying inside galaxy clusters are generally more massive and older than those in low-density regions.
When and how were these distinct properties formed? One promising line of study is to investigate directly the primitive galaxy clusters, “protoclusters”, in the early universe. Especially, we focus on the start of cluster formation. However, only a few high-z protoclusters were found. Therefore, we are searching for new high-z protoclusters in the deep and wide field of Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) Deep fields, and found two protocluster candidates at z~6.
【発表者2】Pan Hsi-An (総研大 D1、指導教官:久野成夫)
【タイトル】Molecular gas and star formation properties of NGC 628
【Abstract】
It is widely accepted that molecular gas is the dominant material of star formation.
Since H2 (molecular hydrogen) is not observable, the second abundant molecular 12CO has become a proxy of tracing molecular gas. However, 12CO is optically thick, which is able to trace the molecular gas at the surface of molecular cloud only.
Therefore the observation in optically thin line, such as 13CO is needed. We observe both 12CO and 13CO toward NGC 628 to constrain the ability of a optically thin line in determining the molecular gas properties and its relation with star formation. Both observation and data analysis are ongoing.

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