Gamma Rays from Star Forming Galaxies and Dark Matter Non-Thermal - PowerPoint PPT Presentation

Massimo Persic INAF+INFN Trieste Gamma Rays from Star Forming Galaxies and Dark Matter

Non-Thermal plasma: T ion electron f( v ) of either species non-Maxwell Boltzmann Particle Acceleration

Radiation Processes synchrotron bremsstrahlung Inverse Compton

4

Diffusion-Loss Equation energy gains / losses diffusion

energy gains / losses diffusion rate of particles production per unit volume of coord space by definition: energy loss for particles of energy E

Energy loss processes: protons l Ionization losses 10 -14 n p (1- 2 ) -1/2 [10.9 + 2 ln -2 ) + (1- -2 )] s -1 p + ln (1- d p p p p 5 10 -15 n p [26.73 + 3 ln( p )] s -1 p > 2000 l Pion production d p 3.7 10 -13 n p ( p -1) p > 2.38 (  1.22 GeV) p -1)m p c 2 (

Energy loss processes: electrons b ( ) = b Coul ( ) + b syn ( ) + b IC ( ) + b brem ( ) + b AW ( ) l Coulomb interactions with thermal electrons l synchrotron radiation l Inverse Compton (IC) scattering … for U r =4 10 -13 erg cm -3 r l bremsstahlung radiation l Scattering by Alfvèn waves ) -1/2 /L = 3 10 -16 (B/ G) n e (L/0.3 kpc) -1 s -1 b AW = - B (4

Coulomb IC Starburst galaxy: n e = 100 cm -3 AW B = 100 G z = 0 Brems Synchrotron Galaxy cluster: n e = 10 -3 cm -3 B = 1 G z = 0

n e =10 -4 , B=1 G hjffyfkyfky Cooling time: t loss = / b ( )

MP, Rephaeli & Arieli 2008, A&A, 486, 143 HE Gamma Rays in Galaxies Rephaeli, Arieli & MP 2010, MNRAS, 401, 473 MP & Rephaeli 2010, MNRAS, 403, 1569 l electron spectrum q N e ( ) = N e,0 l synchr. emissivity 3 /d 2 ) N e,0 a(q) B (q+1)/2 ( /4 10 +6 ) (q 1)/2 erg/(s cm 2 Hz) F = 5.67 10 (r s l electron spectrum: normalization, energy density l particle/field energy density equipartition

l p/e energy density ratio = T 0 = few keV l p/e ratio  q =2.3  U p /U e 15 N p /N e | >>1GeV l equipartition magnetic field B 2 l CRp energy density U p = 8 (1+ ) primary/secondari electron ratio ~ 0.5

Persic, Rephaeli & Arieli 2008 M82 d=3.6 Mpc A&A, 486, 143 r(SB)= 0.3 kpc f 1GHz = 10 Jy Klein+ 1988 SN ~ 0.3 yr erg s  SFR ~10 M yr L m =

(… M82 cont’d) Drury+ 1994 VHE -ray emission SB nucleus : r 0.3 kpc M H2 = M U p = 200 eV cm L >100GeV = s  F >100GeV = cm s External disk: r>0.3 kpc (R) = (0) e R/R d Gas: flat, thin, exponential disk: M g = M (0) = 7.5E+22 cm -2 U p = ( R/R SB ) R d = 0.82 kpc s  F >100GeV = L >100GeV = cm s Total flux: F >100GeV = 1.1 10 -11 cm s

(… M82 cont’d) numerical treatment loss-propagation model … same structure parameters CR/field energy equip. p/e theoretically assumed injection part. spectrum: q=2 ... interactively  N e ~ 10 cm N p /N e ( >>1 GeV ) ~ 50, B 0 ~ 180 G protons electrons F >100MeV = E-8 cm -2 s -1 F >100GeV = 2.5E-12 cm -2 s -1 ≥ 1/2 sens. of MAGIC-II, VERITAS

(… M82 cont’d) M82 detection Physics Today January 2010

NGC 253 Rephaeli, Arieli & Persic 2010, MNRAS, 401, 473 protons total total nucleus electrons differential total spectrum integral spectrum 0 decay IC bremsstr

(… NGC253 cont’d) NGC 253 detection U p ~ 150 eV cm -3 in SB nucleus

2. U p from M31 (Andromeda Galaxy) Abdo et al. (LAT Collab.) -rays 2010, A&A, 523, L2 MW model, scaled U p ~ 0.36 eV cm 3

Large Magellanic Cloud (LMC) MW Abdo et al. (LAT Collab.) HI 2010, A&A, 512, 7 H 2 U p ~ 0.2-0.3 eV cm 3

Abdo et al. (LAT Collab.) Small Magellanic Cloud (SMC) 2010, A&A, 523, A46 U p ~ 0.15 eV cm 3

3 SN / r s Adapted from: l Abdo et al. (LAT Collab.) 2010, ApJL, 709, L152; l Physics Today (Jan. 2010) ~ const, M H galaxy-wide M82 NGC253 MW | | l M31 LMC SMC | l l

Kennicutt 1998 ARAA, 36, 189 Bigiel + 2008 2.5 AJ, 136, 2846 1.4 2.5 1.4 Schmidt-Kennicutt SF law: SFR HI+H 2 ~ 2.5  L SN M H Abdo et al. (LAT Collab.) SFR M H 2010, A&A, 523, L2 SFR (1+1/ SFR 1.4

Measuring CR energy densities ( U p ) in galaxies  U p from -ray emission: . = E/E = ( E/E) -1 t = -1 t ~ 10 5 yr Lifetime for energy gain: Residency lifetime: = out + pp M82: out = 3 10 4 yr M82: pp = 2 10 5 yr Starburst lifetime: SB ~ dyn ~ 10 8 yr ~ 10 5 yr << SB ~ Balance of gains vs losses achieved during SB Equilibrium: min-energy confuguration  CR vs B equipartition p/e ratio   U p from ( radio synchrotron em. of ) CRe  U p from SN rate & residency time: U p SN

Arp 220  U p 475 eV cm 3 radio NGC 253  125 radio, M 82  111 radio, Milky Way  1 … M31  0.35 LMC  0.25 SMC  0.15 U p from supernovae v massive star formation  SN v SNR  Fermi-I mechanism  CR v CR – SN relation ( Ginzburg & Syrovatskii 1964 ) 3 U p ~ ¼ ( SN ) ( E ej ) r s

Arp 220  U p 476 eV cm 3 NGC 253  125 particle SN rate SB radius accel. eff. M 82  111 Milky Way  1 3 U p ~ ¼ ( SN ) ( E ej ) r s M31  0.35 LMC  0.25 protons ’ SMC  0.15 lifetime kin. energy of SN ejecta ~ 2 10 7 n p yr pp collisions pp cn p advection 3 10 4 (r s /0.3 kpc) (v out /2500 km s ) yr 9.0E+3 yr adv Arp 220 515 eV cm -3 3.50 yr -1 0.25 kpc 2.0E+4 yr adv NGC 253 77 eV cm -3 0.12 yr -1 0.20 kpc 2.6E+3 yr adv 95 eV cm -3 M 82 0.25 yr -1 0.26 kpc V<sv 5.0E+6 yr pp 1.8 eV cm -3 MW 0.02 yr -1 2.4 kpc 2.0E+7 yr pp <bhsrs M31 0.7 eV cm -3 0.01 yr -1 4.2 kpc 1.0E+7 yr pp LMC 0.2 eV cm -3 2 E-3 yr -1 3.0 kpc Sngoug 4.0E+7 yr pp SMC 1.0 eV cm -3 1 E-3 yr -1 2.1 kpc n if CRp advected by diffusion v diff =100 km/s  U p =0.15 eV/cm 3

CONCLUSIONS on CRs U p can be measured from: i) -ray emission (directly) ii) radio synchrotron emission (indirectly) , assuming p/e ratio, part./field equilibrium. iii) SN rates and CRp lifetimes. Starbursts: U p ~ O(100) eV cm -3 Quiet SFGs: U p ~ O(1) eV cm -3 Universal(?) acceleration efficiency of SN. Fermi I acceleration at work (NR strong shock) . Particles/field equipartition in place.  radio data to study CRs in high-z SFGs Happy ending?

Targets for DM search Requirements: 1. Not associated with known conventional TeV sources 2. High DM density 3. Close by 4. Not extended 1. Galactic Center Distance ~ 7.5 kpc  OK ... but: other -ray sources in the FOV, i.e. SNR Sgr A East  plausible competing scenarios 2. Dwarf Sph galaxies ok 1(?), 2, 3, 4

1. The Galactic Center 1. The Galactic Center >1 TeV VLA Sgr A MAGIC no variability, Gal. Eq. yr-min scale Detected: Cangaroo 2003 Confirmed: HESS 2004 Confirmed: MAGIC 2005 consistent with Sgr A* to 6’’ Diffuse GP emission revealed and slightly extended by subtracting strong sources Correlation with molecular gas MAGIC vs HESS CRs interacting with MCs agreement ! GC source coincident w. Sgr A* Subtracted image slope = 2.2 Contours of CS emission (molecular tracer) GC signal: GC signal: unlikely unlikely to be DM to be DM

Some background on galaxy structure .. I(r) = I 0 exp(-r/R d ) same profile at all luminosities!

Rotation curves are not self-similar with luminosity!

Smooth progression of RC shape, and disk/halo interplay, with luminosity lkugkfthjfftrd blablablablabla

Tully-Fisher relation R/R opt when DM starts to be dynamically felt

Whence these properties? • Bottom-up • Baryon infall: SF  SN expl.  winds  cosmology: small most of infalling galaxies formed baryons lost in small first, hence their gals., but retained in density retains the bigger ones. cosmological density at the epch • Smaller, denser gals. of their turnaround have little/no SF – ( 1.8). bigger, less dense gals. do have gas and SF.

Small, nearby galaxies … or … large, faraway clusters? Let’s start from signal from self-interacting DM decay D -2  small distances best!  small guys win!  cosmology: dSph halos are best candidates for DM signal  astrophysics: dSph stellar pops . are most silent astroph bkgd

 Dwarf Spheroidals: ideal DM candidates Milky Way satellites  nearby High M/L  DM dominated Old stellar pop.  no ongoing SF u

Bergström & Example: Draco dSph modeling d~80 kpc Hooper 2006 total DM A v>, m : WIMP annihil. cross section, mass annihil. rate N : -rays / annihil. - ray flux cusped upper limit profile cored profile -ray flux r s = 7 – 0.2 kpc 0 = 10 7 – 10 9 M  kpc -3 part. phys 2 r s 3 = 0.03 – 6 M  2 kpc -3 astrophys 0

_ bb + - t t _ min. cored W + W - max. cusped ZZ MAGIC Fermi LAT Bergström & Hooper 2006 40-h exp. 1-yr exp. IACT neutralino detection: < A v> 10 -25 cm 3 s -1 Stoehr + 2003

Draco dSph obs’d MAGIC Albert et al. 2008

Segue-1 galaxy

Wilman-I

Summary Galaxies can produce VHE -rays, related to ongoing SF and DM decay SF: emission detected from nearby starburst (M82, NGC253), quiescent (M31, LMC, SMC), and SB/Seyfert-I (NGC1068, NGC4945) galaxies. CR energy densities: measured directly from -emission and indirectly from radio emission, estimated from SR frequencies  results agree. DM: no signal from MW center and from (best candidate) MW satellite dSph galaxies.  hunt ongoing ...