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超新星遗迹的射电巡天观测和
甚高能伽玛射线源研究
田文武
2008年6月5日在北京大学的报告
射电天文的重大发现
• 1951年，星际HI谱线
• 1965年，3K微波背景
• 1967年，脉冲星, VLBI
• 1968年，星际分子
• 1971年，视超光速运动
• 1974年，脉冲双星/引力波
• ….
概要
• 21厘米中性氢原子(HI)谱线银道面巡天简介及建立新方法
(Tian & Leahy方法)获得可信赖的超新星遗迹和相关联天体
的距离(或范围)
• 超新星遗迹和分子云的相互作用导致很多天体物理现象,如
加速带电粒子到相对论能量, 产生可以观测到的TeV伽玛射
线. 测定天体的距离可以直接检验超新星遗迹是河内宇宙线
粒子起源处的合理性
• 实例: 四个超新星遗迹和TeV源相关联系统:G29.7-0.3/PSR
J1846-0258/HESS J1846-029, G21.5-0.9 /PSR J1833-
1034/HESS J1833-105, G23.3-0.3/HESS 1834-087,G353.6-
0.7/HESS J1731-347; 一个含异常X-光线脉冲的年青超新星
遗迹 G27.4+0.0 /AXP 1E1841+045;一个正与临近大CO分子
云相互作用的超新星遗迹 G18.8+0.3; 及一个产生1720兆赫
兹OH脉泽辐射的年青超新星遗迹 G21.8-0.6.
21-cm HI observations in the Milky Way disk
1420MHz and 13CO data ( + X-ray data)
1420 MHz data from the VLA • 13CO(J=1-0) data from the
Galactic Plane Survey (Still et Galactic ring survey (Jackson et
al. 2006, AJ, 132, 1158):
al.2006, ApJS, 163, 145) by the
Range:18<l<67d, -1.3<b<2.3d Five College Radio Astronomy
FWHM: 1'×1'×1.56 km/s Observatory 14m telescope:
Velocity range:-113– 165 km/s Range:18<l<56d, -1<b<1d
rms :2 K per channel
FWHM:46"x46"x0.21 km/s
Short-spacing information for
rms:~ 0.13 K per channel.
the H I line emission from
observations with the 100m Velocity range: -5-- 135 km/s
Green Bank Telescope
(<=40d), -5-- 85km/s(>=-40d)
An example to build absorption spectra to Kes 75 (a TeV source)
21 cm HI map from VLA+GBT
observations with contours (28 40
60 100 k) overlaid
1420 MHz map from VLA
D-array observations.
Ton (v)-Toff(v)=(Ts-Tbg)(1-e^{-tau})
solid-line box ---> Ton(v)
Annulus background Toff(v)
• HI+CO13 spectra show that the highest absorption velocity~95 km/s, absence of
absorption at ~102 km/s, the tangent point velocity ~110 km/s. So d ~ 5.1 to 7.5 kpc
• Rotation
curve of
Milky Way
stays flat
with
distance
Calculated radial velocity as a function of distance along a
line of sight in the Galactic plane at l = 29.7 degree
Formula: Vr= Ro sin l (V(R)/R – Vo/Ro). V(R):circular orbit
speed of a star; R:Galactocentric radius; Vr:radial velocity
The long-standing puzzle on Kes 75/PSR J1846-0258 is resolved
(Leahy & Tian, 2008, A&A, 480, L25. 已7次独立引用, 改写了前面的结
果:Becker & Helfand, 1984, ApJ, 283, 154,被引用36次)
1. Significant distance revision from ~19 kpc to ~ 6 kpc for Kes 75
gives a normal explosion energy (~2x10E51 erg) from a core
collapse, contrary to the highly implausible value (~10E53 erg) for
an extremely high X-ray luminosity for Kes 75 (~4x10E37 ergs /s)
obtained previously due to d ~ 19 kpc.
2. Small radius ~ 3 pc (1.6') for Kes 75 argues that it harbors a
Crab-like rotation powered young pulsar J1846-0258 and PWN
(723--884 yr) , rather than the previous inferred, much higher ratio
of the pulsar-plus-nebula luminosity to spin-down luminosity.
Kes 73 new results:
1.Absorption features
appear up to tangent
point velocity (~110
km/s)
2.At 114 km/s, the HI
distribution is quite
inhomogeneous.
3.The HI feature at 84
km/s is at the far
distance
Conclusion: Kes 73 is
in front of the HI at
84 km/s, but beyond
the tangent point.
~84 km/s ~110 km/s tangent point
• HI+CO spectra confirm the
above conclusion.
• The CO cloud (~89 km/s) is
behind Kes 73. Limits to
distance of Kes 73/AXP
1E1841-045 between the far
distance (9.4 kpc) of 89 km/s
and the tangent point (7.5 kpc)
which was used as an upper
limit in past 20 yrs.
• Kes 73 has a refined age of 500
to 1000yr, the AXP has a larger
50% X-ray luminosity.
• Tian & Leahy, ApJ, 2008, 677,
692
~89 km/s
• SNR/Cloud interaction
• 1. Detection of high energy gamma
ray and non-thermal X-ray emission
• 2. Detection of 1720 MHz shock-
excited OH masers ---"signposts" of
SNR-molecular cloud interactions.
• 3. Detection of high line rates CO(2-
1)/CO(1-0) and broad wings of 10–
20 km/s in CO and other molecular
Emit TeV gamma-rays
spectra (Moriguch et al. 2005, ApJ,
631, 947).
• 4. Detection of shocked H2 emission
from the system at near-infrared band
(Reach et al. 2005, ApJ, 618, 297).
Schematic of an expanding SNR • Direct method: Determine distance
interacting with an adjacent to a SNR/CO Cloud system by
HI+CO obs.
molecular cloud (Wardle &
Yusef-Zadeh 2002)
The distance to Kes 69 and G21.5-0.9
Green A.J. et al. (1997, AJ, 114, 2058) suggested a far distance (11.2
kpc) of the 1720 MHz OH maser velocity 69.3 km/s by HI+OH obs.
Old OH
maser at
69.3km/s
New OH
Maser at 1 pwn
~84km/s
G21.5-0.9
X-ray (contour --ROSAT PSPC)+radio
(grey from NVSS) image from Yusef-
Zadeh et al. (2003, ApJ, 585, 319) New VLA 1420 MHz map
Kes 69
• HI spectrum: max velocity of
absorption ~86 km/s; HI emission
feature at 113 km/s with no
respective absorption.
• CO image + spectrum: adjoining
cloud at ~ 85 km/s, no prominent
cloud around 70 km/s towards the
bright southern shell.
• New detected 1720 MHz OH maser
at velocity 80-86km/s from within
the southern shell of Kes 69.
• Conclusions: distance of ~5.5 kpc
to Kes 69, and physical interaction
between Kes 69 and adjoining
cloud.
(from Jack Hewitt)
Spitzer image
VLA D-Array y GBT map
Integrated1720 MHz line intensity OH maser Vo=84 km/s
G21.5-0.9 and PMN J1832-1035
1. The highest absorption velocity~66
km/s, no absorption at~71 and 86 km/s
2. G21.5-0.9 is likely at 4.4 – 4.8 kpc
(near side of ~ 71 km/s) or possibly at
4.4 – 8 kpc (far side of ~86 km/s)
http://www.mppmu.mpg.de/~rwagner.sources
The thick-solid line shows the total non-
vFv spectrum of a young
thermal flux.
SNR with an age 10^3 yrs
Hadronic emissions are Pion-decay gamma-
rays (thin-solid), synchrotron (dot-dashed)
and bremsstrahlung emission (short-and-
long dashed) from secondary electrons
produced by charged pion.
Leptonic emissions are synchrotron (long-
dashed), inverse-Compton (dotted) and
bremsstrahlung (short-dashed) emission
by primary electrons.
an old SNR case an old SNR-a GMC an illuminated GMC
The HESS J1731-347 image ( Aharonian et al. 2008, A&A, 477,
353); Contours start at 4 sigma in 1 sigma steps, which is of
gamma-ray excess counts smoothed with a Gaussian filter with
standard deviation 0.1 degree. Energy range:0.50 to 80 TeV.
A power-law fit to the spectral data
(E=N0E^{-Г}),Г=2.26±0.10
Two SNR and TeV HESS source Systems
1. Discovery of the Radio and X-ray counterpart of TeV
gamma-ray Source HESS J1731-347
W.W. Tian(1,2), D.A. Leahy(2), M. Haverkorn(3), B. Jiang(4)
(2008 June 1, ApJL, 679, 85)
• 1. National Astronomical Observatories of China, CAS, China
• 2. Department of Physics & Astronomy, Uni. of Calgary, Canada
• 3. Astronomy Department, Uni. of California-Berkeley, USA
• 4. Department of Astronomy, Uni. of Massachusetts, USA
2.First evidence: an old SNR encounters a GMC to emit
TeV gamma-rays in the cloud: W41/HESS J1834-087
W.W. Tian(1,2), Z, Li(4), D. Leahy(2), Q.D. Wang(4)
(2007, ApJL, 657, 25. 已13次引用, 其中9次独立引用):
SNR G363.6-0.7?
• Left: the continuum image of G353.6-0.7 at 1420 MHz from the Southern
Galactic Plane Survey (SGPS, ATCA data) with a beamsize of 100 arcsec and a
sensitivity of < 1 mJy/beam (Haverkorn et al. 2006, ApJS, 167, 230)
Right: the 843 MHz image from the Molonglo GPS with a beamsize of 43
arcsec and a sensitivity of 1~ 2 mJy/beam (Green et al. 1999, ApJS, 122, 207)
X-ray and IR Images: a likely SNR
Left: ROSAT PSPC image (0.1-2.4 kev), centred at l=353.55, b=-0.6
integration time of 300 s, Signal-to-Noise ratio ~ 5
Right: 8 micro mid-infrared image, centred at l=353.5, b=-0.65 from the
GLIMPSE Legacy survey with resolution of ~2 arcsec (Benjamin et al.
2003, PASP, 115, 953). No thermal emission down to a limit of 0.4 mJy
(5 sigma), G353.6-0.7 is not an HII region!
Spectral Index of G353.6-0.7
Total flux density estimayes of 2.2±0.9 Jy at 1420 MHz and 1.4±0.3 Jy at 5
GHz (Parkes observations, Haynes et al. 1978, Austr. J. of Phys. Suppl. 45, 1)
by same method, give = 0.4(- 0.6/+0.5), favour a non-thermal feature.
The 843 MHz data misses too many low spatial frequency components to be
used to obtain a reliable flux density.
ACTA+Parkes image. The ring shows Azimuthally averaged flux over the low
the boundary of SNR G353.6-0.7. half of G353.6-0.7 as a function of
radius from the center of the remnant.
Distance to G353.6-0.7
Too faint to obtain HI absorption spectrum of the new SNR. HII
region G353.42-0.37 is adjacent to the SNR. The HI absorption
spectrum features in the range of 9 to -24 km/s show G353.42-
0.37 is at the distance (~ 3.2 kpc) of its recombination line
velocity (~ -16 km/s). A number of HESS sources are detected
where high-energy particle accelerators
are located near H II regions, and other
such accelerators without proximate
sources of low-energy photons are weak
or undetected at TeV energies, Helfand et
al. (2007) suggested that TeV emissions
of HESS sources could originate from
inverse Compton scattering of the
starlight from the nearby H II regions.
SNR G353.6-0.7 may be at ~3.2 kpc.
Overlapping Radio (grey)+X-ray (red)+gamma-ray
(green) images of G353.6-0.7
1. The radio and X-ray
morphologies of G353.6-0.7
near-perfectly march the
outline of HESS J1731-347.
2. The low half seen in X-
rays and upper half not seen
in X-rays is likely due to
clouds' absorption, which is
revealed by the 12CO
column density increasing
towards the Galactic plane.
How old is G353.6-0.7?
1. An old SNR: a large angular size of 0.5 degree and a
physical size of ~28 pc in diameter (assuming a distance of
~ 3.2 kpc); faint radio and X-rays.
2. Ambient density n0 ~5 cm-3, estimated by known flux
(~1.2E-11 cm-2 s-1, assuming a conversion efficiency ~ 0.1
and explosion energy 10E51 ergs, Aharronian et al. 2006
ApJ, 636, 777),
3. An age of ~27,000 yr, based on a Sedov model (Cox
1972, ApJ,178, 159), it is entering a radiation phase.
4. It is not too old < 100000 yrs, because the X-rays are
visible in G353.6-0.7 and an old SNR is expected to emit few
W41/HESS J1834-087
• XMM-Newton observations show diffuse X-ray emission
within the HESS source J1834-087--- this suggests an
association between the X-ray and TeV gamma-ray emissions.
• High-resolution 13CO images reveal a giant molecular cloud
(~ 78 km/s) at the center of W41--likely associated with W41.
• Probably, the first evidence that an old SNR encounters a
GMC to produce TeV gamma-rays
• New results (Leahy &Tian 2008, AJ): determining distances
to the W41/cloud system support that such interaction is
physical by analyzing HI and 13CO spectra.
Radio Images of W41/molecular cloud:
1420 MHz continuum map 13CO map from Galactic Ring Survey:
36'x30' in size, F1420=60+/-8 Jy a GMC at the center of W41: MH2~10^5 M0
Alpha>=0.43 (330 -1420 MHz)
NH2 ~10^22 (cm^-2), no ~ 10^3 (cm^-3)
(Fv ~ v^(-alpha)
XMM-NEWTON Observations of W41
An EPIC-pn intensity image in 0.3-1.5 The central part of W41 in 1.5-7
keV. 15 point-like sources are detected keV. A region of enhanced intensity
also. Red circle represents HESS is clearly present coincident with the
J1834-087; small green circle illustrates HESS source, apparently diffuse.
the region for x-ray spectrum. Contours of 13CO emissions at 1.2,
1.4, 1.8 and 2.1k.
W41/CO cloud physical interaction
Two nearby CO features:
at ~77 km/s and ~95 km/s
• The maximum velocity of
HI absorption:~78 km/s. No
absorption at ~95 km/s.
一个正与临近大CO分子云相互作用的超新星遗迹
G18.8+0.3
Tian, Leahy & Wang, 2007, A&A, 474, 541
• Previous observations • HI+13CO observations:
(12CO + HI + OH, Dubner constrain distance to Kes 67;
a GMC at 20km/s is
et al. 1996, AJ, 111, 1304; physically adjoining with the
2004 A&A, 426, 201): SNR.
• 1. Morphological agreement • ROSAT PSPC: a diffuse X-
between one 12CO clump ray feature apparently
and the SNR shock front. associated with part of the
radio shell of the SNR.
• 2. Detection of high line
rates 12CO(2-1)/12CO(1-0) • New 13CO observation: clear
morphological agreement
in a clump. between the SNR and an
• A conclusion: a possible adjoining cloud; broadened
interaction between SN profile seen in the 13CO
shock and an adjoining emission spectrum.
molecular cloud • There likely exists a
physical interaction!
Radio and X-ray images of Kes 67
1420 MHz image HI Image at 18.3 km/s
CO image at 19.8 km/s ROSAT PSPC image (0.5-2.4 kev)
HI and 13CO spectra
1.The largest velocity absorption feature at the tangent point gives a lower
distance limit of 7.6 kpc.
2. Absence of absorption at negative velocities gives upper limit of 15.2 kpc.
3. The broadened profile at ~20 km/s in the 13CO spectrum indicates a
likely SNR/CO cloud interaction and gives a distance of ~12 kpc.
Tangent point
~20 km/s
Summary
• Using HI+13CO spectra determine distances to seven
SNR/PSR/HESS systems: Kes 75~ 6 kpc; Kes 69 ~5.5
kpc, Kes 7--7.5-9.4 kpc, W41--3.9-4.5 kpc, Kes 67~12
kpc, G21.5-0.9--4.4-4.8 kpc, G353.6-0.7~3.2 kpc
• Some values differ greatly from previously published
values, partly because our methods resolve the near/far
distance ambiguity, partly due to better discrimination
against HI emission differences in background spectra.
• Determining distances to SNR/Cloud/TeV HESS
source systems help to trace Galactic CRs origin.
