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Transcript
Latest impacts of
observational (radio) astronomy
Hiroshi Imai
Department of Physics and Astronomy
Graduate School of Science and Engineering
 Introducing “Nature” and “Science” papers
 Latest impacts of radio astronomy (HI’s favorites)
 stars: classification, formation, and evolution
 extra-planets
 interstellar medium
 the Milky Way Galaxy
 cosmology
“Nature” and “Science” journals
Which kind of result has a deep impact published in
these papers in astronomy?
• amazing and/or important topic to researchers
and the public
– unexpected discovery
– solving long-standing (debating) issue
• Type of impacts
– finding new phenomenon, classification
– developing new technique
– implication to new possibility
“Nature” and “Science” journals
What is currently hot topics in (radio) astronomy?
• New type of radio sources (e.g. fast radio bursts)
• Newly found phase of
star formation and stellar evolution
• Newly discovered gas dynamics
• New characteristics of a black hole,
a high-envergy object, and interstellar medium
• Innovative research technique
• Deeper exploration of early universe
Note: not all important works were published in
these major journals.
Galactic and extragalactic astronomy
•
•
•
•
Targets with known and unknown distances
Nearest targets in the universe and others
Individual stars and unresolved star clusters
Present (red shift z~0) and past universe
LMC
D=50 kpc
resolved into
individual stars
M31
D=800 kpc
Unresolved
star clusters
Gas fragmentation
• Dendrogram identification of
hierarchical structures of gas clumps
• Visualization of the process of
gas clump fragmentation
• Lower limit to
self-gravitating clumps of 0.2 pc
Goodman et al. 2009
Gas inflow
through a gap
of a protoplanetary disk
ALMA Cycle-0
•CO emission:
disk rotation
•Inner HCO+:
gas inflow
(7×10-8Msun yr-1)
HD152527 (Cassassus et al., 2013, Nature, 493, 191)
Mass infall onto a massive young stellar object
• identification of a ~20 Msun young stellar object
(Betran et al. 2006)
• outflow, rotation, and infall
Contraction for massive star formation
• Gas toroid mass ~87 Msun
• Magneto-hydrodynamically super-critical contraction
(Girat et al. 2009)
A large coronal loop in Argol
High-precision
astrometry to
trace stars’
positions
Peterson et al., 2010, Nature, 463, 207
A large coronal loop in Argol
• First direct radio imaging of a coronal loop except the Sun
• Giant “dynamo” created by rapidly rotating binary stars
Peterson et al., 2010, Nature, 463, 207
Spiral pattern of mass-loss flow
•
•
Spiral pattern
created by
binary stars
Unexpectedly
large stellar
mass loss
during a
thermal pulse
(for 200 years,
1800 years ago)
ALMA CO J=32 emission observation toward R Sculptoris
(Maercker et al. 2012, Nature, 490, 232)
Sgr A*: the nearest super-massive blackhole
Gilessen et al. 2009; Ghez et al. 2008
• Mass density: 108Msunpc-3
• Movement of the apoastron
• Distance to the Galactic center:
R0=8.33±0.35 kpc
◎
Sgr A* spatially resolved?
• 1AU in size at λ=3.5 mm Shen et al. 2005
• “Event horizon scale” resolved at λ=1.3 mm?
Doeleman et al. (2008)
3.5 mm
uniform weighting
3.5 mm
super-resolution
1.3 mm visibility plot
G2 clouds: passing periastron of Sgr A* in 2014?
See ESO movie
Gillessen et al. 2012
See also
http://www.eso.org/public/videos/
Strong magnetic field nearby Sgr A*
Rotation measure for PSR J1745-2900
(0.12 pc from Sgr A*)
Eatough et al., 2013, Nature, 501, 391
B~2.6 mG
at r~0.12 pc
Enough magnetic
flux accreted onto
the event horizon
to explain electromagnetic emission
flux from BH at Sgr A*
Eatough et al., 2013, Nature, 501, 391
Giant magnetized outflows from the center of
Carretti et al. 2013,
the Milky Way
Nature, 493, 66
(VLA+WMAP)
Magnetic energy transfer (1047 J) from the star formation sites
(within 200 pc from the Galactic center) to the Galactic halo
Exact position of a super massive black hole
Image courtesy of NRAO/AUI and Y.Y. Kovarev, MPIfR and ASC Lebedev
“Core shift” technique
• Optical thickness
dependent on radio
frequency
• Very close to a highfrequency radio core
• Wide opening angle of
the jet in M87
Hada et al. 2011,
Nature, 477, 185
B-mode in cosmic microwave background
sub-millimeter polarimetric measurement
Nature Breaking News on 17 March 2014
B-mode in cosmic microwave background
Using South Pole
Telescope
Nature Breaking News on 17 March 2014
Fundamental
constants dependent
on location?
Fine structure constant α
Electron-proton mass ratio Δμ/μ
Lab. and VLA measurements (Truppe et al. 2013, Nature, open access)
Fast Radio Bursts (FRBs)
New type of transient radio sources
• milli-second
radio flares
(FRB110220, 110627,
110703, 120127)
• Extremely large
dispersion
measures
• Likely located at
cosmological
distance (z>0.5)
SνD~1012Jy kpc2
E~1032J
Thornton et al. 2013, Science, 341, 53
Enjoy astronomical discoveries
with understanding
backgrounds and implications!
Report
Describe which kind of “virtual” scientific theme
is expected to appear in the major journals
such as “Nature” and “Science”. Also show why
you consider so by describing the following
points.
1.Current background
2.Imagined new results
3.Implication of the results