Observations of Mariner IV with the Parkes 210-ft Radio Telescope

Radio telescope test results from Mariner IV OBSERVATION

CO(1-0), CO(2-1) and Neutral Gas in NGC 6946: Molecular Gas in a Late-Type, Gas Rich, Spiral Galaxy

We present "On The Fly" maps of the CO(1-0) and CO(2-1) emission covering a 10' X 10' region of the NGC 6946. Using our CO maps and archival VLA HI observations we create a total gas surface density map, Sigma_gas, for NGC 6946. The predominantly molecular inner gas disk transitions smoothly into an atomic outer gas disk, with equivalent atomic and molecular gas surface densities at R = 3.5' (6 kpc). We estimate that the total H2 mass is 3 X 10^9 Mo, roughly 1/3 of the interstellar hydrogen gas mass, and about 2% of the dynamical mass of the galaxy at our assumed distance of 6 Mpc. The value of the CO(2-1)/CO(1-0) line ratio ranges from 0.35 to 2; 50% of the map is covered by very high ratio, >1, gas. The very high ratios are predominantly from interarm regions and appear to indicate the presence of wide-spread optically thin gas. Star formation tracers are better correlated with the total neutral gas disk than with the molecular gas by itself implying SFR is proportional to Sigma_gas. Using the 100 FIR and 21 cm continuum from NGC 6946 as star formation tracers, we arrive at a gas consumption timescale of 2.8 Gyr, which is relatively uniform across the disk. The high star formation rate at the nucleus appears to be due to a large accumulation of molecular gas rather than a large increase in the star formation efficiency. The mid-plane gas pressure in the outer (R > 10 kpc) HI arms of NGC 6946 is close to the value at the radial limit (10 kpc) of our observed CO disk. If the mid-plane gas pressure is a factor for the formation of molecular clouds, these outer HI gas arms should contain molecular gas which we do not see because they are beyond our detection limit

The volume densities of giant molecular clouds in M83

Using observed GALEX far-ultraviolet (FUV) fluxes and VLA images of the 21-cm HI column densities, along with estimates of the local dust abundances, we measure the volume densities of a sample of actively star-forming giant molecular clouds (GMCs) in the nearby spiral galaxy M83 on a typical resolution scale of 170 pc. Our approach is based on an equilibrium model for the cycle of molecular hydrogen formation on dust grains and photodissociation under the influence of the FUV radiation on the cloud surfaces of GMCs. We find a range of total volume densities on the surface of GMCs in M83, namely 0.1 - 400 cm-3 inside R25, 0.5 - 50 cm-3 outside R25 . Our data include a number of GMCs in the HI ring surrounding this galaxy. Finally, we discuss the effects of observational selection, which may bias our results.Comment: 9 pages, 11 figure

Nuclear Bar Catalyzed Star Formation: 13^CO, C18^O and Molecular Gas Properties in the Nucleus of Maffei 2

(Abridged) We present resolution maps of CO, its isotopologues, and HCN from in the center of Maffei 2. The J=1-0 rotational lines of 12^CO, 13^CO, C18^O and HCN, and the J=2-1 lines of 13^CO and C18^O were observed with the OVRO and BIMA arrays. The 2-1/1-0 line ratios of the isotopologues constrain the bulk of the molecular gas to originate in low excitation, subthermal gas. From LVG modeling, we infer that the central GMCs have n(H_2) ~10^2.75 cm^-3 and T_k ~ 30 K. Continuum emission at 3.4 mm, 2.7 mm and 1.4 mm was mapped to determine the distribution and amount of HII regions and dust. Column densities derived from C18^O and 1.4 mm dust continuum fluxes indicate the CO conversion factor in the center of Maffei 2 is lower than Galactic by factors of ~2-4. Gas morphology and the clear ``parallelogram'' in the Position-Velocity diagram shows that molecular gas orbits within the potential of a nuclear (~220 pc) bar. The nuclear bar is distinct from the bar that governs the large scale morphology of Maffei 2. Giant molecular clouds in the nucleus are nonspherical and have large linewidths. Dense gas and star formation are concentrated at the sites of the x_1-x_2 orbit intersections of the nuclear bar, suggesting that the starburst is dynamically triggered.Comment: 50 pages, 14 figures, accepted for publication in Ap

Ram pressure drag - the effects of ram pressure on dark matter and stellar disk dynamics

We investigate the effects of ram pressure stripping on gas-rich disk galaxies in the cluster environment. Ram pressure stripping principally effects the atomic gas in disk galaxies, stripping away outer disk gas to a truncation radius. We demonstrate that the drag force exerted on truncated gas disks is passed to the stellar disk, and surrounding dark matter through their mutual gravity. Using a toy model of ram pressure stripping, we show that this can drag a stellar disk and dark matter cusp off centre within it's dark matter halo by several kiloparsecs. We present a simple analytical description of this process that predicts the drag force strength and its dependency on ram pressures and disk galaxy properties to first order. The motion of the disk can result in temporary deformation of the stellar disk. However we demonstrate that the key source of stellar disk heating is the removal of the gas potential from within the disk. This can result in disk thickening by approximately a factor of two in gas-rich disks.Comment: Accepted by MNRAS (Oct 2011) 17 pages, 11 figures, 1 tabl

'A new kind of rays': gothic fears, cultural anxieties and the discovery of X-rays in the 1890s

In 1895, the world of modern physics was effectively ushered in with the discovery of X-rays by the German physicist, Wilhelm Conrad Röntgen. X-rays rapidly changed the ways in which the human body was perceived, and their discovery was documented and fiercely debated in scientific articles, newspaper reports, literary writings, cartoons and films. This article examines a range of these responses, both 'scientific' and 'popular', and considers the particular significance of their repeated recourse to the Gothic and the uncanny as a means of expressing both excitement and disquiet at what the new X-ray phenomenon might mean

Solutions of ionic liquids with diverse aliphatic and aromatic solutes – Phase behavior and potentials for applications:A review article

This article principally reviews our research related to liquid–liquid and solid–liquid phase behavior of imidazolium- and phosphonium-based ionic liquids, mainly having bistriflamide ([NTf2]−) or triflate ([OTf]−) anions, with several aliphatic and aromatic solutes (target molecules). The latter include: (i) diols and triols: 1,2-propanediol, 1,3-propanediol and glycerol; (ii) polymer poly(ethylene glycol) (PEG): average molecular mass 200, 400 and 2050 – PEG200 (liquid), PEG400 (liquid) and PEG2050 (solid), respectively; (iii) polar aromatic compounds: nicotine, aniline, phenolic acids (vanillic, ferulic and caffeic acid,), thymol and caffeine and (iv) non-polar aromatic compounds (benzene, toluene, p-xylene). In these studies, the effects of the cation and anion, cation alkyl chain and PEG chain lengths on the observed phase behaviors were scrutinized. Thus, one of the major observations is that the anion – bistriflamide/triflate – selection usually had strong, sometimes really remarkable effects on the solvent abilities of the studied ionic liquids. Namely, in the case of the hydrogen-bonding solutes, the ionic liquids with the triflate anion generally exhibited substantially higher solubility than those having the bistriflamide anion. Nevertheless, with the aromatic compounds the situation was the opposite – in most of the cases it was the bistriflamide anion that favoured solubility. Moreover, our other studies confirmed the ability of PEG to dissolve both polar and non-polar aromatic compounds. Therefore, two general possibilities of application of alternative, environmentally acceptable, solvents of tuneable solvent properties appeared. One is to use homogeneous mixtures of two ionic liquids having [NTf2]− and [OTf]− anions as mixed solvents. The other, however, envisages the application of homogeneous and heterogeneous (PEG + ionic liquid) solutions as tuneable solvents for aromatic solutes. Such mixed solvents have potential applications in separation of the aforesaid target molecules from their aqueous solutions or in extraction from original matrices. From the fundamental point of view the phase equilibrium studies reviewed herein and the diversity of the pure compounds – ionic liquids and target molecules – represent a good base for the discussion of interactions between the molecules that exist in the studied solutions

A Chandra X-ray Analysis of Abell 1664: Cooling, Feedback and Star Formation in the Central Cluster Galaxy

The brightest cluster galaxy (BCG) in the Abell 1664 cluster is unusually blue and is forming stars at a rate of ~ 23 M_{\sun} yr^{-1}. The BCG is located within 5 kpc of the X-ray peak, where the cooling time of 3.5x10^8 yr and entropy of 10.4 keV cm^2 are consistent with other star-forming BCGs in cooling flow clusters. The center of A1664 has an elongated, "bar-like" X-ray structure whose mass is comparable to the mass of molecular hydrogen, ~ 10^{10} M_{\sun} in the BCG. We show that this gas is unlikely to have been stripped from interloping galaxies. The cooling rate in this region is roughly consistent with the star formation rate, suggesting that the hot gas is condensing onto the BCG. We use the scaling relations of Birzan et al. 2008 to show that the AGN is underpowered compared to the central X-ray cooling luminosity by roughly a factor of three. We suggest that A1664 is experiencing rapid cooling and star formation during a low-state of an AGN feedback cycle that regulates the rates of cooling and star formation. Modeling the emission as a single temperature plasma, we find that the metallicity peaks 100 kpc from the X-ray center, resulting in a central metallicity dip. However, a multi-temperature cooling flow model improves the fit to the X-ray emission and is able to recover the expected, centrally-peaked metallicity profile.Comment: 15 pages, 13 figure

Warm Molecular Gas in Dwarf Starburst Galaxies: CO(3-2) Observations

Eight dwarf starburst galaxies have been observed with the Caltech Submillimeter Observatory (CSO) telescope in the CO J= 3 - 2 transition. The galaxies observed are He 2-10, NGC 5253, NGC 1569, NGC 3077, Haro 2, Haro 3, II Zw 40 and Mrk 86; all but the last two are detected. The central regions of He 2-10 and NGC 5253 were mapped and a CO(2-1) spectrum of NGC 5253 was obtained. The error weighted mean CO(3-2)/CO(1-0) ratio of the detected galaxies is 0.60$\pm$0.06, which is virtually identical to what is found for starbursts in the nuclei of nearby spirals, and suggests that the molecular gas is optically thick, warm (T$_{k}>$20 K), and moderately dense ($n_{H_{2}}\sim 10^{3-4} cm^{-3}$). The CO(3-2)/CO(1-0) ratio peaks at or close to the starburst in all cases. CO emission does not appear to be optically thin in these dwarfs, despite the low metallicity and intense radiation fields, which is probably because in order for CO to exist in detectable amounts it must be self-shielding and hence optically thick. Physical properties of the molecular clouds in these dwarf starbursts appear to be essentially the same as nearby spiral nuclei, with the possible exception that CO is more confined to the cloud cores.Comment: 21 pages, 8 figures; Accepted for publication by the Astronomical Journa

Development of competences while solving real industrial interdisciplinary problems: a successful cooperation with industry

The development of projects in industrial context constitutes an exceptional opportunity for engineering students to develop competences expected by the labour market. Therefore, the adoption of this type of interaction within engineering curricula is highly recommended, not only at the end of the degree, but also in the previous years. The main purpose of this paper is to present and analyse a Project-Based Learning (PBL) semester in which six teams of Industrial Engineering and Management (IEM) students integrate different areas of knowledge, while solving real problems of five companies, emphasizing the technical solutions developed by the students and the feedback provided by the companies. Students' feedback will be also addressed. The main outcomes of this study reveal that most of the technical solutions lie in areas of Lean applications and ergonomic improvement of workplaces. Companies were very pleased with the results of this type of University-Business Cooperation (UBC).This work was funded by COMPETE-POCI-01-0145-FEDER-007043 and FCT-UID-CEC-00319-2013info:eu-repo/semantics/publishedVersio