Absorption-Line Probes of Gas and Dust in Galactic Superwinds

We discuss moderate resolution spectra of the NaD absorption-line in a sample of 32 far-IR-bright starburst galaxies. In 18 cases, the line is produced primarily by interstellar gas, and in 12 of these it is blueshifted by over 100 km/s relative to the galaxy systemic velocity. The absorption-line profiles in these outflow sources span the range from near the galaxy systemic velocity to a maximum blueshift of 400 to 600 km/s. The outflows occur in galaxies systematically viewed more nearly face-on than the others. We therefore argue that the absorbing material consists of ambient interstellar gas accelerated along the minor axis of the galaxy by a hot starburst-driven superwind. The NaD lines are optically-thick, but indirect arguments imply total Hydrogen column densities of N_H = few X 10^{21} cm^{-2}. This implies that the superwind is expelling matter at a rate comparable to the star-formation rate. This outflowing material is very dusty: we find a strong correlation between the depth of the NaD profile and the line-of-sight reddening (E(B-V) = 0.3 to 1 over regions several-to-ten kpc in size). The estimated terminal velocities of superwinds inferred from these data and extant X-ray data are typically 400 to 800 km/s, are independent of the galaxy rotation speed, and are comparable to (substantially exceed) the escape velocities for $L_*$ (dwarf) galaxies. The resulting loss of metals can establish the mass-metallicity relation in spheroids, produce the observed metallicity in the ICM, and enrich a general IGM to 10$^{-1}$ solar metallicity. If the outflowing dust grains survive their journey into the IGM, their effect on observations of cosmologically-distant objects is significant.Comment: 65 pages, including 16 figures. ApJ, in pres

Extremely High Energy Neutrinos, Neutrino Hot Dark Matter, and the Highest Energy Cosmic Rays

Extremely high energy (up to 10**(22) eV) cosmic neutrino beams initiate high energy particle cascades in the background of relic neutrinos from the Big Bang. We perform numerical calculations to show that such cascades could contribute more than 10% to the observed cosmic ray flux above 10**(19) eV if neutrinos have masses in the electron volt range. The required intensity of primary neutrinos could be consistent with astrophysical models for their production if the maximum neutrino energy reaches to 10**(22) eV and the massive neutrino dark matter is locally clustered. Future observations of ultra high energy cosmic rays will lead to an indirect but practical search for neutrino dark matter.Comment: 4 latex pages, 3 postscript figures included, uses revtex.sty and psfig.sty. Submitted to Physical Review Letter

Variability in bioreactivity linked to changes in size and zeta potential of diesel exhaust particles in human immune cells

Acting as fuel combustion catalysts to increase fuel economy, cerium dioxide (ceria, CeO(2)) nanoparticles have been used in Europe as diesel fuel additives (Envirox™). We attempted to examine the effects of particles emitted from a diesel engine burning either diesel (diesel exhaust particles, DEP) or diesel doped with various concentrations of CeO(2) (DEP-Env) on innate immune responses in THP-1 and primary human peripheral blood mononuclear cells (PBMC). Batches of DEP and DEP-Env were obtained on three separate occasions using identical collection and extraction protocols with the aim of determining the reproducibility of particles generated at different times. However, we observed significant differences in size and surface charge (zeta potential) of the DEP and DEP-Env across the three batches. We also observed that exposure of THP-1 cells and PBMC to identical concentrations of DEP and DEP-Env from the three batches resulted in statistically significant differences in bioreactivity as determined by IL-1β, TNF-α, IL-6, IFN-γ, and IL-12p40 mRNA (by qRT-PCR) and protein expression (by ELISPOT assays). Importantly, bioreactivity was noted in very tight ranges of DEP size (60 to 120 nm) and zeta potential (−37 to −41 mV). Thus, these physical properties of DEP and DEP-Env were found to be the primary determinants of the bioreactivity measured in this study. Our findings also point to the potential risk of over- or under- estimation of expected bioreactivity effects (and by inference of public health risks) from bulk DEP use without taking into account potential batch-to-batch variations in physical (and possibly chemical) properties

Constraints on star-formation driven galaxy winds from the mass-metallicity relation at z=0

We extend a chemical evolution model relating galaxy stellar mass and gas-phase oxygen abundance (the mass-metallicity relation) to explicitly consider the mass-dependence of galaxy gas fractions and outflows. Using empirically derived scalings of galaxy mass with halo virial velocity in conjunction with the most recent observations of z~0 total galaxy cold gas fractions and the mass-metallicity relation, we place stringent global constraints on the magnitude and scaling of the efficiency with which star forming galaxies expel metals. We demonstrate that under the assumptions that metal accretion is negligible and the stellar initial mass function does not vary, efficient outflows are required to reproduce the mass-metallicity relation; without winds, gas-to-stellar mass ratios >~ 0.3 dex higher than observed are needed. Moreover, z=0 gas fractions are low enough that while they have some effect on the magnitude of outflows required, the slope of the gas fraction--stellar mass relation does not strongly affect our conclusions on how the wind efficiencies must scale with galaxy mass. Despite systematic uncertainties in the normalization and slope of the mass-metallicity relation, we show that the metal expulsion efficiency zetaw=(Zw/Zg)etaw (where Zw is the wind metallicitiy and Zg is the interstellar medium metallicity) must be both high and scale steeply with mass. Specifically, we show that zetaw >> 1 and zetaw proportional to vvir^-3 or steeper. In contrast, momentum- or energy-driven outflow models suggest that etaw should scale as vvir^-1 or vvir^-2, respectively, implying that the Zw-Mstar relation should be shallower than the Zg-Mstar relation. [abridged]Comment: MNRAS, in press; 22 pages, 13 figures. Several structural changes, including a new section on varying the IMF (yield

Nuclear starburst-driven evolution of the central region in NGC 6764

We study the CO and the radiocontinuum emission in an active galaxy to analyze the interplay between the central activity and the molecular gas. We present new high-resolution observations of the CO(1-0) and CO(2-1) emission lines, and 3.5 cm and 20 cm radio continuum emission in the central region of the LINER/starburst galaxy NGC 6764. The galaxy has an outflow morphology in radio continuum, spatially coincident with the CO and H$\alpha$ emission, and centered slightly off the radio continuum peak at the LINER nucleus. The total molecular gas mass in the center is about 7x10^8 \msun, using a CO luminosity to total molecular gas conversion factor that is three times lower than the standard one. CO(1-0) emission is found near the boundaries of the radio continuum emission cone. The outflow has a projected expansion velocity of 25 km/s relative to the systemic velocity of NGC6764. About 4x 10^6 \msun of molecular gas is detected in the outflow. The approximate location (~1 kpc) of the dynamical inner Lindblad resonance has been derived from the rotation curve. The peak of the CO emission is slightly (< 200 pc) offset from the peak of the radio continuum. The molecular gas has most likely been ejected by the stellar winds from the recent starburst, but the CO line ratios show indication of an interaction with the AGN. The energy released by the nuclear starburst is sufficient to explain the observed outflow, even if the data cannot exclude the AGN from being the major energy source. Comparison of the outflow with hydrodynamical simulations suggests that the nuclear starburst is 3--7 Myr old and the bubble-like outflow is still confined and not freely expanding.Comment: Accepted for publication in A&

Piecing together the puzzle of NGC 5253: abundances, kinematics and WR stars

We present Gemini-S/GMOS-IFU optical spectroscopy of four regions near the centre of the nearby (3.8 Mpc) dwarf starburst galaxy NGC 5253. This galaxy is famous for hosting a radio supernebula containing two deeply embedded massive super star clusters, surrounded by a region of enhanced nitrogen abundance that has been linked to the presence of WR stars. We detected 11 distinct sources of red WR bump (CIV) emission over a 20" (~350 pc) area, each consistent with the presence of ~1 WCE-type star. WC stars are not found coincident with the supernebula, although WN stars have previously been detected here. We performed a multi-component decomposition of the H\alpha\ line across all four fields and mapped the kinematics of the narrow and broad (FWHM = 100-250 km/s) components. These maps paint a picture of localised gas flows, as part of multiple overlapping bubbles and filaments driven by the star clusters throughout the starburst. We confirm the presence of a strong H\alpha\ velocity gradient over ~4.5" (~80 pc) coincident with the region of N/O enhancement, and high gas density known from previous study, and interpret this as an accelerating ionized gas outflow from the supernebula clusters. We measure the ionized gas abundances in a number of regions in the outer IFU positions and combine these with measurements from the literature to assess the radial abundance distribution. We find that the O/H and N/H profiles are consistent with being flat. Only the central 50 pc exhibits the well-known N/O enhancement, and we propose that the unusually high densities/pressures in the supernebula region have acted to impede the escape of metal-enriched hot winds from the star clusters and allow them to mix with the cooler phases, thus allowing these freshly processed chemicals to be seen in the optical.Comment: 16 pages, accepted to A&

Advances in perturbative thermal field theory

The progress of the last decade in perturbative quantum field theory at high temperature and density made possible by the use of effective field theories and hard-thermal/dense-loop resummations in ultrarelativistic gauge theories is reviewed. The relevant methods are discussed in field theoretical models from simple scalar theories to non-Abelian gauge theories including gravity. In the simpler models, the aim is to give a pedagogical account of some of the relevant problems and their resolution, while in the more complicated but also more interesting models such as quantum chromodynamics, a summary of the results obtained so far are given together with references to a few most recent developments and open problems.Comment: 84 pages, 18 figues, review article submitted to Reports on Progress in Physics; v2, v3: minor additions and corrections, more reference

Star forming dwarf galaxies

Star forming dwarf galaxies (SFDGs) have a high gas content and low metallicities, reminiscent of the basic entities in hierarchical galaxy formation scenarios. In the young universe they probably also played a major role in the cosmic reionization. Their abundant presence in the local volume and their youthful character make them ideal objects for detailed studies of the initial stellar mass function (IMF), fundamental star formation processes and its feedback to the interstellar medium. Occasionally we witness SFDGs involved in extreme starbursts, giving rise to strongly elevated production of super star clusters and global superwinds, mechanisms yet to be explored in more detail. SFDGs is the initial state of all dwarf galaxies and the relation to the environment provides us with a key to how different types of dwarf galaxies are emerging. In this review we will put the emphasis on the exotic starburst phase, as it seems less important for present day galaxy evolution but perhaps fundamental in the initial phase of galaxy formation.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.). Lisbon, September 2010, Springer Verlag, in pres

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde