宇宙线起源中天文学前沿问题

Q. Daniel Wang

南京大学 and University of Massachusetts

Why Cosmic Ray (CR) in Astronomy?

• Universe as the lab of particle physics

• energy density 1 eV/cm^3 + diffuse speed ---> production rate of ~10^41 erg/s --- 10% the mechanical energy from all SNe or 10x the X-ray luminosity of hot plasma --- a major energetic component of the Galactic ecosystem or even the entire universe!

 Energy spectrum of primary cosmic rays (Nagano (09)

Decomposition of the CR spectrum

• Only very roughly!

• Why is it  hard to determine CR origins?• mostly charged

particles+B --> direction information is mostly lost or at least uncertain.

• Therefore, need to study CRs astronomically, via radiation and possible neutrinos

T. K. Gaisser, T. Stanev, S. Tilav ， Frontiers of Physics, Volume 8, Issue 6, pp.748-758

三种银河系成份的Hillas模型

Are individual SNRs the dominant source?

Evidence for CRA is convincing!• nonthermal X-ray • Halpha-line --> energetics of CR acceleration; What is the

electron to proton energy ratio? • gamma-ray imaging and spectra: pion_0 decay in the 0.05-

0.2 GeV range and radiation  up to ~ PeV energies (not achieved yet?).

Multiwavelength imagery (top) and gamma-ray spectra (bottom) of supernova remnants W44 and IC443. Credit: NASA/DOE/Fermi LAT Collaboration, Chandra X-ray Observatory, ESA Herschel/XMM-Newton

Unsettling issues of the SNR CR paradiagm

• How do lepton and hadron particles share the SN energy?

• How energetic could CRs be in SNRs?

• need statistical studies (Yuan)

• coverage at GeV and > 10 TeV

Are superbubbles more important?

• environments of SNe

• energetics • composition • why superbubbles:

large-scales, B-amplification, collective effects from multiple shocks and stellar winds.

• What is the exact mechanism for the acc, at which stage? blow-out.

Could the nuclear star formation produce the Fermi bubbles?

• CR --> gamma-ray

• PeV-CR+RF --> e- e+ --> haze

• pp --> e-e+ --> cold annihilation cloud

• there are smaller bubbles from the disk, but with softer spectra: confusion with other source (e.g., brems?)  or propagation effect? small-to-intermediate scale anisotropy structures: superbubble contributions? • Cygnus region

Su et al. 2010

Planck haze (arXiv:1208.5483) Overlaid on Fermi Bubbles

Bartoli, B. et al. (14)

Are AGNs responsible for higher energy CRs?

• Past AGN activity of Sgr A* TeV point and diffuse emissions.

• SMBH activities are episodic!

• various reflections, responsible for the Fermi bubbles?

How do CRs shape the ISM and hence the evolution of galaxies?

Why other galaxies? • bird-eye view• CR effects:

• heating• driving outflows

How do galaxies loss CRs?

• Not much gamma-ray information radio survey edge-on galaxies and RM Are galaxies lepton calorimeters? spectral index

• FRM+soft X-ray --> B_org intensity distribution

• polarization -->  B_org orientation

• radio emission+spectral distribution+flow dynamics --> B_tot + CRe density distributions

• ideally measurements of IC to check (currently only upper limits). With these, one can model the outflow and/or diffusion of CRs  more reliably

How do the intragroup/intracluster media treat?

• Do accretion or merger shocks produce CRs?

• Radio observations have shown that galaxy clusters are giant reservoirs of CR

• Gamma-ray limit from Fermi on the average CR-to-thermal energy ratio of 4.6% for a photon index of 2.4 (Huber et al. 13).

• But CRs could be important in the central region: Perseus central galaxy

• ongoing radio - X-ray observations

• Is the ICM a hadron calorimeter?

• X-ray+SZ+weak lensing measurements --> distribution of CR pressure, especially in outer regions

• FRM measurement --> B field• modeling

WSRT at 1.4 GHz image showing the north and south radio relics. ROSAT X-ray emission is shown by the red contours. (van Weeren et al. 2010)

Are other CR sources important?

• Magnetars, PWN, and jets

• radio galaxiesGRBs ...

How to produce the most energetic CRs?

• Cen A,

Hillas diagram

How do CRs propagate?

Illustration: Alan Stonebraker

How do  CRs interact with the IGM?

• GZK effect• Where does the

energy go? pre-heating the IGM or radiation via cascading?

• IGM B field• observations of

extragalactic gamma-ray and neutrino backgrounds

• How does the propagation shape CR energetics?

Galactic center PWN

Combined in pulsar rest frame

Jet

Counter Jet

Trail

B2224+65 and Guitar Nebula

• Period = 0.68 s• Ės =1.2 x 1033 erg s−1

• ts ~ 1.1 Myr• Distance ~ 1 kpc• Proper motion ~ 900 km/s• A bow shock nebula in Hα

(Cordes et al. 1993).• A linear X-ray feature

apparently stemming from pulsar, but ∼118o offset from its proper motion direction (Wong et al. 2003; Zavlin & Pavlov 2004; Hui & Becker 2007).

• This linear feature (main jet) showing a consistent proper motion (Johnson & Wang 2010).

Image: Courtesy of Shami Chatterjee and James M. Cordes Cornell University

Pulsar proper motion direction

How do interact with the ISM (including RF)?

• diffuse gamma as a tracer

• large-scale isotropy --> co-rotation of CRs (energy dependent?) with the Galactic B field

• model B field based on the combination of radio and FR

• How do CRs interact with the ISM (including RF)?

Are local CRs presentative?

• stochastic events propagation effects

Anisotropy in Galactic coordinate

Tibet III

Icecube

Cosmic ray flows in three directions

Inward flowsOutward flowsElectrically neutral state

Excess

X.B.Qu et al., ApJ, 750, L17 2012

Snowden et al. 1995,

Krause et al. (2014)

Summary and conclusions

Issues with DSA in SNRs• the measured index p~3 is substantially steeper than

the range that is plausibly expected in linear and non-linear DSA models (Alfven wave damping in dense gas).

• However, no sources were observed at E > 10 TeV

CR Interactions in the Interstellar Medium

e+-

PHe

CNO

X,γ

gas

gas

ISRF

e+-

π+-

P_

LiBeB

ISM

diffusion energy losses reacceleration convection etc.

π0

synchrotron

IC

bremss

Chandra

GLAST

ACEhelio-modulation

p

42 sigma (2003+2004 data)

HESS Preliminary

SNR RX J1713-3946

PSF

B

HeCNO

Flux

20 GeV/n

CR species: Only 1 location modulation

e+-

π+-

PAMELABESS

AMS

© Strong,Moskalenko,Reimer 2009

• To distinguish the hadronic and leptonic origins– Sensitive measurements at > 10 TeV– And at < 0.1 TeV

• Given also the large amount of energy that such a beam may contain, which can be of the order of a few percent of the inner jet power, our results suggest that the detection by Chandra of the narrow X-ray jets that remain straight on scales beyond several hundred kpc provides observational evidence that the relativistic inner jets of blazars, first of all the flat-spectrum radio quasars, are powerful accelerators of UHE cosmic rays. Detection of high-energy neutrinos from FSRQs with Ice-Cube or a Northern Hemisphere high-energy neutrino telescope will provide strong support for this scenario.

• Some questions for CHANGES galaxies from cosmic-ray viewpoint :

• 1. Do they support the na.ve expectations of standard electron propagation?

• = injection in disk, propagation with energy losses in halo by diffusion

• and/or convection.• The test: spectral index variations

with distance from disk.• 2. If YES - we can get the

propagation parameters and compare with Milky Way,

• where we have much more detailed information but are inside it.

• 3. If NO - what revisions are required, is the 'standard model' any use at all?

• Are things just too complicated in reality?

• Back to the drawing board?• 4. If SOMETIMES – where and why

does it break down?• 5. Is there a cosmic-ray disk and a

halo, or just a halo as assumed in many models?

• 6. Lepton calorimeters? - FIR-radio correlation.

Contour lines: ASCA X-raysY. Uchiyama et al. 2002

“Both scenarios with aleptonic, or hadronic primaryparticle distribution are ableto accommodate anexponential–cutoff shape

Modeling of the SED of SNRs:

Maximum electron energy: upt to ~1 PeV

GeV-TeV emission: IC + Bremss + 0 decay

The energy of the non-thermal particles is a significantfraction of the kinetic energy released in a core-collapsedsupernova, which requires highly efficient particleacceleration in Cas A.

Very much depend on the density of the ambient gas.Araya & Cui 2010

Galaxy luminosity over 20 decades of energy

S-PASSSouthern SkyParkes Telescope2.3 GHzPolarized intensityCarretti et al.Nature 493, 66(2 Jan 2013)

Correlates with Fermi Bubbles.Produced by repeated episodes of star-formation at Galactic Centre?

年轻超新星或银心等激波加速宇宙线 --

与背景光子（ ~1eV）反应产生膝和 TeV的 e+e-

比如，超新星爆发

激波面e+e-

宇宙线proton

光子背景~1eV

> PeV的质子高于产生 e+e-的阈能

< PeV的质子低于产生 e+e-的阈能