Evaluation of organic markers for chemical mass balance source apportionment at the Fresno Supersite

International audienceSources of PM2.5 at the Fresno Supersite during high PM2.5 episodes occurring from 15 December 2000?3 February 2001 were estimated with the Chemical Mass Balance (CMB) receptor model. The ability of source profiles with organic markers to distinguish motor vehicle, residential wood combustion (RWC), and cooking emissions was evaluated with simulated data. Organics improved the distinction between gasoline and diesel vehicle emissions and allowed a more precise estimate of the cooking source contribution. Sensitivity tests using average ambient concentrations showed that the gasoline vehicle contribution was not resolved without organics. Organics were not required to estimate hardwood contributions. The most important RWC marker was the water-soluble potassium ion. The estimated cooking contribution did not depend on cholesterol because its concentrations were below the detection limit in most samples. Winter time source contributions were estimated by applying the CMB model to individual and average sample concentrations. RWC was the largest source, contributing 29?31% of measured PM2.5. Hardwood and softwood combustion accounted for 16?17% and 12?15%, respectively. Secondary ammonium nitrate and motor vehicle emissions accounted for 31?33% and 9?15%, respectively. The gasoline vehicle contribution (3?10%) was comparable to the diesel vehicle contribution (5?6%). The cooking contribution was 5?19% of PM2.5. Fresno source apportionment results were consistent with those estimated in previous studies

Deep 1.1 mm-wavelength imaging of the GOODS-South field by AzTEC/ASTE -- II. Redshift distribution and nature of the submillimetre galaxy population

We report the results of the counterpart identification and a detailed analysis of the physical properties of the 48 sources discovered in our deep 1.1mm wavelength imaging survey of the GOODS-South field using the AzTEC instrument on the Atacama Submillimeter Telescope Experiment (ASTE). One or more robust or tentative counterpart candidate is found for 27 and 14 AzTEC sources, respectively, by employing deep radio continuum, Spitzer MIPS & IRAC, and LABOCA 870 micron data. Five of the sources (10%) have two robust counterparts each, supporting the idea that these galaxies are strongly clustered and/or heavily confused. Photometric redshifts and star formation rates (SFRs) are derived by analyzing UV-to-optical and IR-to-radio SEDs. The median redshift of z~2.6 is similar to other earlier estimates, but we show that 80% of the AzTEC-GOODS sources are at z>2, with a significant high redshift tail (20% at z>3.3). Rest-frame UV and optical properties of AzTEC sources are extremely diverse, spanning 10 magnitude in the i- and K-band photometry with median values of i=25.3 and K=22.6 and a broad range of red colour (i-K=0-6). These AzTEC sources are some of the most luminous galaxies in the rest-frame optical bands at z>2, with inferred stellar masses of (1-30) x 10^{10} solar masses and UV-derived star formation rates of SFR(UV) > 10-1000 solar masses per year. The IR-derived SFR, 200-2000 solar masses per year, is independent of redshift or stellar mass. The resulting specific star formation rates, SSFR = 1-100 per Gyr, are 10-100 times higher than similar mass galaxies at z=0, and they extend the previously observed rapid rise in the SSFR with redshift to z=2-5. These galaxies have a SFR high enough to have built up their entire stellar mass within their Hubble time. We find only marginal evidence for an AGN contribution to the near-IR and mid-IR SEDs. (abridged)Comment: 31 pages including 14 figures, accepted for publication in the MNRAS. A higher quality Figure 1 is also included as Figure1.jp

Intelligence Studies, Universities and Security

This article offers a critical assessment of academic intelligence studies in higher education. It argues that universities (and academics) should value this subject far more highly than they currently do. Doing so will enhance better public understanding of an increasingly important and unique device in modern governance. It will also improve the quality of intelligence activity by raising awareness of both good and bad practice, encourage lawfulness by means of public understanding and so defending a vital public service from ill-informed attacks in today’s conflicted world. This, rather than training potential officers, should be the primary purpose of intelligence studies

A Correlation Between Galaxy Morphology and MgII Halo Absorption Strength

(Abridged) We compared the quantified morphological properties of 37 intermediate redshift MgII absorption selected galaxies to the properties of the absorbing halo gas, observed in the spectra of background quasars. The galaxy morphologies were measured using GIM2D modeling of Hubble Space Telescope WFPC-2 images and the absorbing gas properties were obtained from HIRES/Keck and UVES/VLT quasar spectra. We found a 3.1 sigma correlation between galaxy morphological asymmetries normalized by the quasar-galaxy projected separations, A/D, and the MgII rest-frame equivalent widths. Saturation effects cause increased scatter in the relationship with increasing W_r(2796). We defined a subsample for which the fraction of saturated pixels in the absorption profiles is f_sat<0.5. The correlation strengthened to 3.3 sigma. We also find a paucity of small morphological asymmetries for galaxies selected by MgII absorption as compared to those of the general population of field galaxies, as measured in the Medium Deep Survey. The K-S probability that the two samples are drawn from the same galaxy population is ruled out at a 99.8% confidence level. The A/D-W_r(2796) correlation suggests a connection between the processes that perturb galaxies and the quantity of gas in their halos, normalized by the impact parameter. Since the perturbations are minor, it is clear that dramatic processes or events are not required for a galaxy to have an extended halo; the galaxies appear "normal". We suggest that common, more mild processes that populate halos with gas, such as satellite galaxy merging, accretion of the local cosmic web, and longer-range galaxy-galaxy interactions, consequently also induce the observed minor perturbations in the galaxies.Comment: Accepted for publication in the Astrophysical Journa

AzTEC Millimetre Survey of the COSMOS Field - II. Source Count Overdensity and Correlations with Large-Scale Structure

We report an over-density of bright sub-millimetre galaxies (SMGs) in the 0.15 sq. deg. AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z <~ 1.1. This portion of the COSMOS field shows a ~ 3-sigma over-density of robust SMG detections when compared to a background, or "blankfield", population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG over-density is most significant in the number of very bright detections (14 sources with measured fluxes S(1.1mm) > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities and infers an over-density significance of >> 4. We find that the over-density and spatial correlation to optical-IR galaxy density are most consistent with lensing of a background SMG population by foreground mass structures along the line of sight, rather than physical association of the SMGs with the z <~ 1.1 galaxies/clusters. The SMG positions are only weakly correlated with weak-lensing maps, suggesting that the dominant sources of correlation are individual galaxies and the more tenuous structures in the region and not the massive and compact clusters. These results highlight the important roles cosmic variance and large-scale structure can play in the study of SMGs.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in MNRA

The AzTEC/SMA Interferometric Imaging Survey of Submillimeter-Selected High-Redshift Galaxies

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies with the Submillimeter Array, including high-resolution (beam size ~2 arcsec) imaging of eight additional AzTEC 1.1mm selected sources in the COSMOS Field, for which we obtain six reliable (peak S/N>5 or peak S/N>4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N>4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric followup. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology - including the nature of submillimeter galaxies with multiple radio counterparts and constraints on the physical scale of the far infrared - of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim submillimeter galaxies that peaks at higher redshift than previous, radio-selected samples. In particular, the presence of such a population of high-redshift sources has important consequences for models of galaxy formation - which struggle to account for such objects even under liberal assumptions - and dust production models given the limited time since the Big Bang.Comment: 11 pages, 7 figures, accepted for publication in Ap

In search of the authentic nation: landscape and national identity in Canada and Switzerland

While the study of nationalism and national identity has flourished in the last decade, little attention has been devoted to the conditions under which natural environments acquire significance in definitions of nationhood. This article examines the identity-forming role of landscape depictions in two polyethnic nation-states: Canada and Switzerland. Two types of geographical national identity are identified. The first – what we call the ‘nationalisation of nature’– portrays zarticular landscapes as expressions of national authenticity. The second pattern – what we refer to as the ‘naturalisation of the nation’– rests upon a notion of geographical determinism that depicts specific landscapes as forces capable of determining national identity. The authors offer two reasons why the second pattern came to prevail in the cases under consideration: (1) the affinity between wild landscape and the Romantic ideal of pure, rugged nature, and (2) a divergence between the nationalist ideal of ethnic homogeneity and the polyethnic composition of the two societies under consideration

Galactic winds - how to launch galactic outflows in typical Lyman-break galaxies

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2013 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We perform hydrodynamical simulations of a young galactic disc embedded in a hot gaseous halo using parameters typical for Lyman-break galaxies (LBGs). We take into account the (static) gravitational potentials due to a dark matter halo, a stellar bulge and a disc of stars and gas. Star formation is treated by a local Kennicutt–Schmidt law. We simplify the structure of the interstellar medium (ISM) by restricting the computational domain to a 25th of the full azimuthal angle, effectively assuming large-scale axisymmetry and neglecting any effects of spiral structure and focus on the large-scale ISM drivers, the superbubbles. Supernovae are triggered randomly and have preset event sizes of several tens to hundreds. We further investigate different halo gas pressures and energy injection methods. Many of our simulated galaxies, but not all, develop bipolar outflows. We characterize the strength of the outflow by mass and energy outflow rates, and investigate the effect of changes to the details of the model. We find that supernovae are more effective if comprised into larger superbubbles. The weight and the pressure of the halo gas is able to quench galactic outflows. The wind emerges from a series of superbubbles in regions where a critical star formation density is exceeded. The superbubbles expand into the gaseous halo at slightly supersonic speed, producing radiative shock waves with similar characteristics as the absorption systems observed around LBGs.Peer reviewe