Galactic Radio Science Cornelia C Lang University of

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Galactic Radio Science Cornelia C. Lang University of Iowa Eleventh Synthesis Imaging Workshop Socorro,

Galactic Radio Science Cornelia C. Lang University of Iowa Eleventh Synthesis Imaging Workshop Socorro, NM, June 10 -17, 2008

Outline • Radio Emission: what can we learn? – Thermal and non-thermal continuum emission

Outline • Radio Emission: what can we learn? – Thermal and non-thermal continuum emission – Spectral line radiation – The radio spectrum & interferometers • A Radio Tour of the Milky Way – – Star birth and death in the ISM Stellar radio sources Interstellar gas: ionized & atomic clouds Exotic radio sources • An Unusual Place: Galactic Center 2

Radio Emission Mechanisms 3 • Synchrotron radiation - continuum • Energetic charged particles accelerating

Radio Emission Mechanisms 3 • Synchrotron radiation - continuum • Energetic charged particles accelerating along magnetic field lines (non-thermal) • What can we learn? • particle energy • strength of magnetic field • polarization • orientation of magnetic field

Radio Emission Mechanisms 4 • Thermal emission - continuum • Blackbody radiation for objects

Radio Emission Mechanisms 4 • Thermal emission - continuum • Blackbody radiation for objects with T~3 -30 K • Brehmsstralung “free-free” radiation: charged particles interacting in a plasma at T; e- accelerated by ion • What can we learn? H image • mass of ionized gas • optical depth • density of electrons in plasma • rate of ionizing photons Courtesy of Dana Balser

Radio Emission Mechanisms • What we measure from radio continuum • Radio flux or

Radio Emission Mechanisms • What we measure from radio continuum • Radio flux or flux density at different frequencies Flux or Flux Density • Spectral index , where S ~ Spectral index across a SNR thermal no n- th = -0. 1 er m al = -0 . 7 From T. Delaney Frequency 5

Radio Emission Mechanisms 6 • Spectral line emission - Discrete transitions in atoms and

Radio Emission Mechanisms 6 • Spectral line emission - Discrete transitions in atoms and molecules Atomic Hydrogen “spin-flip” transition 21 cm Molecular Lines CO, CS, H 20, Si. O, etc. ! Recombination Lines outer transitions of H H 166 , H 92 , H 41 • What can we learn? (1. 4, 8. 3 GHz, 98 GHz) • gas physical conditions (n, T) • kinematics (Doppler Effect)

Also a wide variety of instruments! ATA CA, USA 7 VLA/EVLA NM, USA ATCA,

Also a wide variety of instruments! ATA CA, USA 7 VLA/EVLA NM, USA ATCA, Australia Millimeter > 15 GHz < 10 mm Low-Frequency < 1. 4 GHz >1 m Centimeter 1. 4 MHz - 15 GHz 20 cm – 1 cm ALMA, Chile Pd. B, France CARMA, CA, USA SMA, Hawaii, USA GMRT, India LOWFAR, NL LWA, NM, USA

Tour of the Galaxy: Interstellar 8 • Low Mass Star Formation - obscured regions

Tour of the Galaxy: Interstellar 8 • Low Mass Star Formation - obscured regions of the Galaxy with high resolution - collimated outflows powered by protostar – 10000 s AU Chandler & Richer 2001 Zapata et al. 2005 VLA 7 mm spectral line (Si. O) – 0. 5” SMA 1 mm spectral line (CO 2 -1) – 1”

Tour of the Galaxy: Interstellar 9 • Probing massive stars in formation - tend

Tour of the Galaxy: Interstellar 9 • Probing massive stars in formation - tend to be forming in clusters; confusion! go to high frequencies (sub-mm) - “hot molecular cores” (100 -300 K) around protostars; complex chemistry Ceph A-East d=725 pc; black=SMA 875 m; green=VLA 3 cm; lines=sub-mm species Spatial resolutions of <1” (where 1”~0. 004 pc or ~750 AU) from Brogan et al. (2007)

Tour of the Galaxy: Interstellar 10 • High Mass Stars in HII Regions -

Tour of the Galaxy: Interstellar 10 • High Mass Stars in HII Regions - high resolution shows objects forming of size ~1000 s AU! - ultra-compact HIIs are < 0. 1 pc with densities n > 104 cm-3 W 49 VLA 7 mm continuum De. Pree et al. (2004)

Tour of the Galaxy: Interstellar 11 • HII regions: ionization & kinematics - continuum

Tour of the Galaxy: Interstellar 11 • HII regions: ionization & kinematics - continuum Lyman photons = # stars - continuum density, mass of ionized H - RRLs kinematics, physical conditions H 92 a velocity distribution Sickle HII region Quintuplet Pistol Nebula (Lang, Goss & Wood 1997) +20 to -60 km/s (Lang, Goss & Morris 2001)

Tour of the Galaxy: Stellar Sources • Stars: Middle Age and Evolving “Radio H-R

Tour of the Galaxy: Stellar Sources • Stars: Middle Age and Evolving “Radio H-R Diagram” from Stephen White 12

Tour of the Galaxy: Stellar Sources 13 • Stars: Very low mass and brown

Tour of the Galaxy: Stellar Sources 13 • Stars: Very low mass and brown dwarfs - some M+L type dwarfs, brown dwarfs show quiescent and flaring nonthermal emission (Berger et al. 2001 -7; Hallinan et al. (2006, 2008) <-- magnetic activity at the poles: electrons interact with dwarf’s magnetic field to produce radio waves that then are amplified by masers OFF ON

Tour of the Galaxy: Stellar Sources 14 • Stars: Middle Age and Evolving Cyg.

Tour of the Galaxy: Stellar Sources 14 • Stars: Middle Age and Evolving Cyg. OB 2 #5– stellar wind emission Contreras et al. (1996) • Binary system with two O 7 I stars • Mass loss ~ 4 -5 x 10 -5 Mo year-1 WR 140 Dougherty et al. (2005) • WR star and O-star binary • Nonthermal, varying emission traces wind-wind collision

Tour of the Galaxy: Interstellar • Supernova Remnants Rudnick et al. Cassiopeia A SNR

Tour of the Galaxy: Interstellar • Supernova Remnants Rudnick et al. Cassiopeia A SNR VLA 6 cm image d = 3 kpc Cassiopeia Gaensler & Frail G 5. 4 -1. 2 and PSR B 1757 -24 d = 5 kpc Sagittarius PSR moving 1, 000 miles/sec 15

Tour of the Galaxy: Interstellar 16 • Star Death: Pulsar Wind Nebulae Chandra X-ray

Tour of the Galaxy: Interstellar 16 • Star Death: Pulsar Wind Nebulae Chandra X-ray Image G 54 VLA B-field Chandra X-ray Image 2. 5’ @ d=2 kpc ~ 1. 4 pc 2. 7’ @ d=5 kpc ~ 3. 8 pc G 54. 1+0. 3 VLA 6 cm Lang, Clubb, Wang & Lu, in prep. Crab radio studies: particle energies, polarization, magnetic field orientation VLA/VLBA pulsar proper motion can be combined with spin-axis orientation (X-ray) Pulsar timing and discovery done with single dish radio telescopes – Parkes, GBT

17 Tour of the Galaxy: Interstellar • HI absorption against bright sources - Interferometer

17 Tour of the Galaxy: Interstellar • HI absorption against bright sources - Interferometer resolves out Galactic HI emission features, allows the study of small-scale features Local bubble ~100 pc Cold HI scale height (2 z) ~200 pc From C. Brogan ~500 pc 3 c 138

Tour of the Galaxy: Interstellar 18 • HI absorption toward 3 c 138 VLBA:

Tour of the Galaxy: Interstellar 18 • HI absorption toward 3 c 138 VLBA: ‘ 95, ‘ 99, 2002 Resolution: 20 mas = 10 AU at 500 pc Changes in t indicate changes in density of Galactic atomic gas Sizescale of features ~ 25 AU! Brogan et al. (2005)

19 Tour of the Galaxy: Exotic • LS I+61 303 : A pulsar comet

19 Tour of the Galaxy: Exotic • LS I+61 303 : A pulsar comet around a hot star? - well known radio, X-, ray, source - high mass X-ray binary with 12 solar mass Be star and NS Orbital Phase -----10 AU - radio emission models: (a) accretion-powered jet or (b) rotation powered pulsar -VLBA data support pulsar model in which particles are shockaccelerated in their interaction with the Be star wind/disk environment VLBA 3. 6 cm; 3 days apart! Note shift of centroid around orbit Astrometry is good to rms = 0. 2 AU (Dhawan, Mioduszewski & Rupen 2006)

Tour of the Galaxy: Exotic • LS I+61 303 : A pulsar comet around

Tour of the Galaxy: Exotic • LS I+61 303 : A pulsar comet around a hot star? Orbit greatly exaggerated VLBA emission vs. orbital phase Be star (with wind/disk) Dhawan, Mioduszewski & Rupen (2006) 20

Tour of the Galaxy: The Galactic Center • Our Galactic center (GC) is 25,

Tour of the Galaxy: The Galactic Center • Our Galactic center (GC) is 25, 000 ly away (8000 pc) • GC lies behind 30 visual magnitudes of dust and gas 21

Center of our Galaxy VLA 20 cm VLA 1. 3 cm VLA 3. 6

Center of our Galaxy VLA 20 cm VLA 1. 3 cm VLA 3. 6 cm Sgr. A* - 4 milliion Mo black hole source Credits: Lang, Morris, Roberts, Yusef-Zadeh, Goss, Zhao 22

Tour of the Galaxy: The Galactic Center • Magnetic Field: Pervasive vs. Local? VLA

Tour of the Galaxy: The Galactic Center • Magnetic Field: Pervasive vs. Local? VLA 90 cm VLA 3. 6 & 6 cm polarization B-field Nord et al. 2004 Lang & Anantharamaiah, in prep. 23

Tour of the Galaxy: The Galactic Center 24 Galactic Center Survey Numerous new compact

Tour of the Galaxy: The Galactic Center 24 Galactic Center Survey Numerous new compact and shell-like sources (massive star formation) D and C array - 4. 9 GHz Full polarization ~1 hour per pointing First high-resolution VLA polarimetric study on large scales! Preliminary results <----- C-array (Lang, Drout, Lazio and Golap, in prep. )

25 Summary • Radio Interferometry: a powerful tool – Physical insight into many different

25 Summary • Radio Interferometry: a powerful tool – Physical insight into many different processes – Spatial scales comparable or better than at other wavelengths: multi-wavelength approach • A great time for students & interferometry! – Amazing science opportunities with new tools CARMA ATA EVLA LOFAR ALMA LWA