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Lawrence Livermore Lab. California, 94550, USA. (Some of the possible) Astrophysical origins of high energy cosmic rays. Diego F. Torres email@example.com. www.angelfire.com/id/dtorres. Summary. Plausible sources? Comments on basic observational features of the CR spectrum.
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California, 94550, USA
Diego F. Torres
To accelerate a particle efficiently it must cross the shocks several times. A general estimate of the maximal energy that can be achieved is given by the requirement:
Rg=E/(Z e B)~R
where Rg is the gyroradius and R is the size of the accelerating region. This can be written as:
R~110 Z-1E20/B-6 kpc
One shot acceleration
The upper limit on the energy of one-shot acceleration is similar to the shock acceleration case. For instance, the maximum energy that can be obtained from a pulsar is
E = W Ze B r2 /c
where W is the pulsar angular velocity, B the surface magnetic field and r the neutron star radius. Typical potential drops are ~1018 V.
Within statistical errors and systematic uncertainties introduced by hadronic interaction models, the data seem to indicate that iron is the dominant component of CRs between 1017 and 1019 eV.
17 h data
Aharonian et al. 2005, A&A, astro-ph/0501667
Confirmation of an extended, steady, hard, source above 1 TeV.
No counterpart yet found.
Anchordoqui et al. astro-ph/0311002
Galactic neutrons of 1018 eV?
Neutrons appear by photodisintegration of Fe nuclei on site at the source. High energy n produce the AGASA excess. Lower energy neutrons decay in flight.
Hard to detect in ICECUBE, but oscillate to muon neutrinos.
Anti-neutrinos take only 1/103 of the n energy
4 events/yr, above 90% CL.
The only cross-confirmed
result for CRs?
Lower energy analysis: no evidence of anisotropy
1017.9—1018.3 eV: AGASA shows a 4s effect from the Galactic plane (Cygnus + Center). Other experiments seems to point in the same direction.
For the UHECRs: two-coordinates analysis show no effect for correlations in scales larger than 10 degrees, above 3s. There might be anisotropies, but the signal is at too low a level to detect it.
The lonely neutrinos.
Radio to g-ray energy distribution of 3C 279 in low and high state measured in January and February, 1996. Wehrle et al. (1998).
General features are a) strong flux variability, b) spectral variability, especially when flaring, and c) the dominance of the gamma-ray emission over all other wavelengths.
For a photon energy of 1 MeV, and a luminosity of 1048 erg s-1, the optical depth is t > 200 / (tv/1 day)
(Indication for beamed emission: Distance is not a problem)
If the emission is beamed -> special relativistic effects
scattering of low energy photons
the speed vh with which the head of a jet advances into the intergalactic medium of particle density ne can be obtained by balancing the momentum flux in the jet against the momentum flux of the surrounding medium. Measured in the frame comoving with the advancing head,
In the jet
Balance between acceleration and losses.
Cen A: 3.4 Mpc M87: 16 Mpc
Directionality should be persistent in the Auger data under the assumption that the mag. field is not too large so as to add substantially to the travel time.
Possible neutron signal which decay in flight close to the Earth preserving directionality and producing an spike in the direction of the source (part. Cen A)
1st step: convective blow-out of a nucleus previously accelerated in a SNR
2nd step: re-acceleration in the super-wind region
Romero et al. 1999, Anchordoqui et al. 2003
M82 NGC 253
ASS + extragal.
5 years, 25 events in PAO
Anchordoqui, Reucroft, Torres, astro-ph/0209546
Only one ULIRG within the 100 Mpc sphere [Arp 220]
Tens of LIRGs (with infrared luminosities >1011 LSUN).
High energy detectability (e.g. g-rays) depends on the combined effect of distance and starburst activity.
Arp 299 (VV 118), one of the the brightest infrared source within 70 Mpc and a system of colliding galaxies showing intense starburst, appeared in the list of candidates for the AGASA triplet
[review on LIRGs and ULIRGs: Sanders and Mirabel, ARA&A, 1996]
Arp 220: 72 Mpc, largest
Star formation and SN explosion rates known in the universe.
Torres et al. astro-ph/0411429, 0407240, 0405302
Further analysis and
about another 10 possible candidates in:
AGASA experiment uncertainty is rather over estimated in the correlation analysis with point sources. The selected angular bin size is perhaps motivated by their earlier autocorrelation analysis (Tinyakov & Tkachev 2001.a), in which the clustering bin size is defined as the uncertainties in the arrival direction of each cosmic ray added in quadrature, e = 21/2 x error ~2.5 deg (as in Uchihori et al.)
To test an alignment between BL LACs and UHECRs, a more reasonable choice for e is to consider just the uncertainty in the CR arrival direction. There is only 1 positional coincidence between the AGASA sample and the 22 selected BL Lacs within an angular bin size of 1.8 deg.
! Strong changes in results due to bin sizes ! Not a good signal.
Torres 2004, Torres et al. 2003.
Left: Time-evolution of a galactic encounter, viewed along the orbital axis. Here dark halo matter is shown in red, bulge stars are yellow, disk stars in blue, and the gas in green.
Right: showing only gas in both galaxies
Barnes and Hernquist 1996
BL Lac Mrk421
Most BL Lacs are successfully modelled with pure or dominant SSC models.
BL LACs -> FSRQs
Ghisellini, Fossati, Celloti, et al.
Increasing importance of the external radiation field
[in the case of PIC models where photopion interactions dominates the initiation of the cascade]
Attenuation length of γ ’s, p’s and 56Fe’s in various background radiations as a function of energy. The 3 lowest and left-most thin solid curves refer to gamma rays, showing the attenuation by IR, CMB, and radio backgrounds. The upper, right-most thick solid curves refer to propagation of protons in the CMB, showing separately the effect of pair production and photopion production. The dashed–dotted line indicates the adiabatic fractional energy loss at the present cosmological epoch. The dashed curve illustrates the attenuation of iron nuclei.
Large M, with high average gas density, and enhanced cosmic ray density
Recent HCN-line survey of Gao & Solomon (2004) of IR and CO-bright galaxies, and nearby spirals
Allows estimate of SFR (from HCN luminosity) and minimum required k for detection by LAT and IACTs (from HCN + CO intensities and distance)
Several nearby starburst galaxies and a number of LIRGs and ULIRGs are plausible candidates for detection
CR Enhancement required for detectability/LATDetectability of LIRGs