CO Transitions Research Articles

HIGH- J CO VERSUS FAR-INFRARED RELATIONS IN NORMAL AND STARBURST GALAXIES

We present correlations between 9 CO transition ($J=4-3$ to $12-11$) and beam-matched far-infrared (Far-IR) luminosities ($L_{\mathrm{FIR},\,b}$) among 167 local galaxies, using {\it{Herschel}} Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (SPIRE; FTS) spectroscopic data and Photoconductor Array Camera and Spectrometer (PACS) photometry data. We adopt entire-galaxy FIR luminosities ($L_{\mathrm{FIR},\,e}$) from the {\it{IRAS}} Revised Bright Galaxy Sample and correct to $L_{\mathrm{FIR},\,b}$ using PACS images to match the varying FTS beam sizes. All 9 correlations between $L'_{\mathrm{CO}}$ and $L_{\mathrm{FIR},\,b}$ are essentially linear and tight ($\sigma$=0.2-0.3 dex dispersion), even for the highest transition, $J=12-11$. This supports the notion that the star formation rate (SFR) is linearly correlated with the dense molecular gas ($n_{\mathrm{H}_2}\gtrsim10^{4-6}\,cm^{-3}$). We divide the entire sample into three subsamples and find that smaller sample sizes can induce large differences in the correlation slopes. We also derive an average CO spectral line energy distribution (SLED) for the entire sample and discuss the implied average molecular gas properties for these local galaxies. We further extend our sample to high-{\it{z}} galaxies with CO $J=5-4$ data from the literature as an example, including submillimeter galaxies (SMGs) and "normal" star-forming BzKs. BzKs have similar FIR/CO(5-4) ratios as that of local galaxies, an follow well the locally-determined correlation, whereas SMG ratios fall around or slightly above the local correlation with large uncertainties. Finally, by including Galactic CO($J=10-9$) data as well as very limited high-{\it{z}} CO $J=10-9$ data, we verify that the CO(10-9) -- FIR correlation successfully extends to Galactic young stellar objects, suggesting that linear correlations are valid over 15 orders of magnitude.

A COMBINEDSPITZERANDHERSCHELINFRARED STUDY OF GAS AND DUST IN THE CIRCUMBINARY DISK ORBITING V4046 Sgr

We present results from a spectroscopic Spitzer and Herschel mid-to-far-infrared study of the circumbinary disk orbiting the evolved (age ~12-23 Myr) close binary T Tauri system V4046 Sgr. Spitzer IRS spectra show emission lines of [Ne II], H_2 S(1), CO_2 and HCN, while Herschel PACS and SPIRE spectra reveal emission from [O I], OH, and tentative detections of H_2O and high-J transitions of CO. We measure [Ne III]/[Ne II] < 0.13, which is comparable to other X-ray/EUV luminous T Tauri stars that lack jets. We use the H_2 S(1) line luminosity to estimate the gas mass in the relatively warm surface layers of the inner disk. The presence of [O I] emission suggests that CO, H_2O, and/or OH is being photodissociated, and the lack of [C I] emission suggests any excess C may be locked up in HCN, CN and other organic molecules. Modeling of silicate dust grain emission features in the mid-infrared indicates that the inner disk is composed mainly of large (r~5 um) amorphous pyroxene and olivine grains (~86% by mass) with a relatively large proportion of crystalline silicates. These results are consistent with other lines of evidence indicating that planet building is ongoing in regions of the disk within ~30 AU of the central, close binary.

The structure of the Cepheus E protostellar outflow: The jet, the bowshock, and the cavity

Context. Protostellar outflows are a crucial ingredient of the star-formation process. However, the physical conditions in the warm outflowing gas are still poorly known.Aims. We present a multi-transition, high spectral resolution CO study of the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow and to constrain the physical conditions of the various components in order to understand the origin of the mass-loss phenomenon.Methods. We have observed the J = 12–11, J = 13–12, and J = 16–15 CO lines at high spectral resolution with SOFIA/GREAT and the J = 5–4, J = 9–8, and J = 14–13 CO lines with HIFI/Herschel towards the position of the terminal bowshock HH377 in the southern outflow lobe. These observations were complemented with maps of CO transitions obtained with the IRAM 30 m telescope (J = 1–0, 2–1), the Plateau de Bure interferometer (J = 2–1), and the James Clerk Maxwell Telescope (J = 3–2, 4–3).Results. We identify three main components in the protostellar outflow: the jet, the cavity, and the bowshock, with a typical size of 1.7″ × 21″, 4.5″, and 22″ × 10″, respectively. In the jet, the emission from the low-J CO lines is dominated by a gas layer at T kin = 80–100 K, column density N (CO) = 9 × 1016 cm-2 , and density n (H2 ) = (0.5−1) × 105 cm-3 ; the emission of the high-J CO lines arises from a warmer (T kin = 400–750 K), denser (n (H2 ) = (0.5−1) × 106 cm-3 ), lower column density (N (CO) = 1.5 × 1016 cm-2 ) gas component. Similarly, in the outflow cavity, two components are detected: the emission of the low-J lines is dominated by a gas layer of column density N (CO) = 7 × 1017 cm-2 at T kin = 55–85 K and density in the range (1−8) × 105 cm-3 ; the emission of the high-J lines is dominated by a hot, denser gas layer with T kin = 500–1500K, n (H2 ) = (1−5) × 106 cm-3 , and N (CO) = 6 × 1016 cm-2 . A temperature gradient as a function of the velocity is found in the high-excitation gas component. In the terminal bowshock HH377, we detect gas of moderate excitation, with a temperature in the range T kin ≈ 400–500 K, density n (H2 ) ≃ (1 −2) × 106 cm-3 and column density N (CO) = 1017 cm-2 . The amounts of momentum carried away in the jet and in the entrained ambient medium are similar. Comparison with time-dependent shock models shows that the hot gas emission in the jet is well accounted for by a magnetized shock with an age of 220–740 yr propagating at 20–30 km s-1 in a medium of density n (H2 ) = (0.5−1) × 105 cm-3 , consistent with that of the bulk material.Conclusions. The Cep E protostellar outflow appears to be a convincing case of jet bowshock driven outflow. Our observations trace the recent impact of the protostellar jet into the ambient cloud, produing a non-stationary magnetized shock, which drives the formation of an outflow cavity.

Fine-structure line deficit in S 140

We try to understand the gas heating and cooling in the S 140 star forming region by spatially and spectrally resolving the distribution of the main cooling lines with GREAT/SOFIA. We mapped the fine structure lines of [OI] (63 {\mu}m) and [CII] (158 {\mu}m) and the rotational transitions of CO 13-12 and 16-15 with GREAT/SOFIA and analyzed the spatial and velocity structure to assign the emission to individual heating sources. We measure the optical depth of the [CII] line and perform radiative transfer computations for all observed transitions. By comparing the line intensities with the far-infrared continuum we can assess the total cooling budget and measure the gas heating efficiency. The main emission of fine structure lines in S 140 stems from a 8.3'' region close to the infrared source IRS 2 that is not prominent at any other wavelength. It can be explained by a photon-dominated region (PDR) structure around the embedded cluster if we assume that the [OI] line intensity is reduced by a factor seven due to self-absorption. The external cloud interface forms a second PDR at an inclination of 80-85 degrees illuminated by an UV field of 60 times the standard interstellar radiation field. The main radiation source in the cloud, IRS 1, is not prominent at all in the fine structure lines. We measure line-to-continuum cooling ratios below 10^(-4), i.e. values lower than in any other Galactic source, rather matching the far-IR line deficit seen in ULIRGs. In particular the low intensity of the [CII] line can only be modeled by an extreme excitation gradient in the gas around IRS 1. We found no explanation why IRS 1 shows no associated fine-structure line peak, while IRS 2 does. The inner part of S 140 mimics the far-IR line deficit in ULIRGs thereby providing a template that may lead to a future model.

Molecular Gas Excitation and Chemistry in VV 114 and NGC 1614 with ALMA

AbstractWe present high resolution molecular line observations of dusty AGN and starburst in nearby luminous infrared galaxies (LIRGs), VV 114 (band 3/4/7) and NGC 1614 (band 3/6/7/9), with ALMA. Multi-frequency imaging from 4.8 GHz to 691 GHz of NGC 1614 allows us to study spatial properties of the radio-to-FIR continuum and multiple CO transitions, and we find the CO excitation up to Jupp = 6 can be explained by a single ISM model powered by nuclear starbursts. Our processing line imaging survey for VV 114 detected at least 30 molecular lines which show different chemical composition from region to region. Multi-molecule imaging helps us to diagnose the chemical differences of dusty ISM, while multi-transition imaging allows us to investigate gas physical conditions affected by nuclear activities directly.

Structural Transition in an Ionic Liquid Controls CO2 Electrochemical Reduction

Broad-band multiplex vibrational sum-frequency generation spectroscopy (SFG) was used to study CO2 reduction on a polycrystalline Ag electrode with a room-temperature ionic liquid (RTIL) electrolyte, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4), with 0.3 mol % water. The Ag/RTIL/H2O system has been shown to reduce CO2 with low overpotential and, depending on water concentration, with Faradaic efficiency of nearly 100% (Rosen, B. A.; Salehi-Khojin, A.; Thorson, M. R.; Zhu, W.; Whipple, D. T.; Kenis, P. J. A.; Masel, R. I. Science 2011, 334, 643–644). The adsorbed CO created by CO2 reduction was probed with infrared (IR) pulses tuned to the CO stretch. Nonresonant (NR) SFG was used to probe the double layer. SFG showed that CO binds weakly to Ag at the CO2 reduction threshold of −1.33 V (vs Ag/AgCl), so CO does not poison the surface. At potentials equal to or more negative than the threshold, the curvature of the parabolic potential-dependent NR intensity significantly increased, and the Stark ...

THE 2014 ALMA LONG BASELINE CAMPAIGN: OBSERVATIONS OF THE STRONGLY LENSED SUBMILLIMETER GALAXY HATLAS J090311.6+003906 AT z = 3.042

We present initial results of very high resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the $z$=3.042 gravitationally lensed galaxy HATLAS J090311.6+003906 (SDP.81). These observations were carried out using a very extended configuration as part of Science Verification for the 2014 ALMA Long Baseline Campaign, with baselines of up to 15 km. We present continuum imaging at 151, 236 and 290 GHz, at unprecedented angular resolutions as fine as 23 milliarcseconds (mas), corresponding to an un-magnified spatial scale of ~180 pc at z=3.042. The ALMA images clearly show two main gravitational arc components of an Einstein ring, with emission tracing a radius of ~1.5". We also present imaging of CO(10-9), CO(8-7), CO(5-4) and H2O line emission. The CO emission, at an angular resolution of ~170 mas, is found to broadly trace the gravitational arc structures but with differing morphologies between the CO transitions and compared to the dust continuum. Our detection of H2O line emission, using only the shortest baselines, provides the most resolved detection to date of thermal H2O emission in an extragalactic source. The ALMA continuum and spectral line fluxes are consistent with previous Plateau de Bure Interferometer and Submillimeter Array observations despite the impressive increase in angular resolution. Finally, we detect weak unresolved continuum emission from a position that is spatially coincident with the center of the lens, with a spectral index that is consistent with emission from the core of the foreground lensing galaxy.

Simplified models of stellar wind anatomy for interpreting high-resolution data

Recent high-resolution observations have shown stellar winds to harbour complexities which strongly deviate from spherical symmetry, generally assumed as standard wind model. One such morphology is the archimedean spiral, generally believed to be formed by binary interactions, which has been directly observed in multiple sources. We seek to investigate the manifestation in the observables of spiral structures embedded in the spherical outflows of cool stars. We aim to provide an intuitive bedrock with which upcoming ALMA data can be compared and interpreted. By means of an extended parameter study, we model rotational CO emission from the stellar outflow of asymptotic giant branch stars. To this end, we develop a simplified analytical parametrised description of a 3D spiral structure. This model is embedded into a spherical wind, and fed into the 3D radiative transfer code LIME, which produces 3D intensity maps throughout velocity space. Subsequently, we investigate the spectral signature of rotational transitions of CO of the models, as well as the spatial aspect of this emission by means of wide-slit PV diagrams. Additionally, the potential for misinterpretation of the 3D data in a 1D context is quantified. Finally, we simulate ALMA observations to explore the impact of interefrometric noise and artifacts on the emission signatures. The spectral signatures of the CO rotational transition v=0 J=3-2 are very efficient at concealing the dual nature of the outflow. Only a select few parameter combinations allow for the spectral lines to disclose the presence of the spiral structure. The inability to disentangle the spiral from the spherical signal can result in an incorrect interpretation in a 1D context. Consequently, erroneous mass loss rates would be calculated...

A macro-scale experimental study of sub- and super-critical CO2 flow behaviour in Victorian brown coal

Abstract In deep coal seams carbon dioxide (CO 2 ) exists in its super-critical state, which emphasizes the importance of studying super-critical CO 2 flow behaviour in coal, especially for field applications, such as CO 2 sequestration and enhanced coal bed methane recovery. Although there has been some research on the subject, the studies have been conducted on only certain types of coal (e.g., naturally fractured black coal) using small coal samples, which makes it difficult to verify the applicability of adsorption theories at a higher scale to estimate field CO 2 storage capacity. The main objective of this study is therefore to determine the permeability behaviour of coal for sub-critical and super-critical CO 2 flows using large coal specimens (203 mm in diameter and 1000 mm in length). A series of core flooding experiments was conducted on brown coal specimens collected from the Latrobe Valley basin, Victoria, using an advanced core flooding apparatus, for a range of injection pressures (6–10 MPa) at 11 MPa axial stress and 38 °C temperature. According to the test results, CO 2 permeability in coal may reduce with increasing injection pressure due to the phase transition of CO 2 from sub-critical to super-critical during pressure increment. N 2 injection into a coal mass permeated with CO 2 shows lower permeability values compared to N 2 injection into a fresh coal mass, because in the former case, the coal mass structure has already been critically reformed during the CO 2 flood. Although the pressure development trends for first N 2 , CO 2 and second N 2 injections along the sample are similar, there may be a noticeable pressure reduction, especially closer to the injection point during the second N 2 injection. This is due to the coal structure re-arrangement during the CO 2 flood, where the pressure development is less in the regions, when CO 2 is in the super-critical state. Such CO 2 and N 2 migration patterns through coal seams after injection are highly important for field applications.

EVIDENCE FOR DECAY OF TURBULENCE BY MHD SHOCKS IN THE ISM VIA CO EMISSION

We utilize observations of sub-millimeter rotational transitions of CO from a Herschel Cycle 2 open time program ("COPS", PI: J. Green) to identify previously predicted turbulent dissipation by magnetohydrodynamic (MHD) shocks in molecular clouds. We find evidence of the shocks expected for dissipation of MHD turbulence in material not associated with any protostar. Two models fit about equally well: model 1 has a density of 10$^{3}$ cm$^{-3}$, a shock velocity of 3 km s$^{-1}$, and a magnetic field strength of 4 ${\mu}$G; model 2 has a density of 10$^{3.5}$ cm$^{-3}$, a shock velocity of $2$ km s$^{-1}$, and a magnetic field strength of 8 $\mu$G. Timescales for decay of turbulence in this region are comparable to crossing times. Transitions of CO up to $J$ of 8, observed close to active sites of star formation, but not within outflows, can trace turbulent dissipation of shocks stirred by formation processes. Although the transitions are difficult to detect at individual positions, our Herschel-SPIRE survey of protostars provides a grid of spatially-distributed spectra within molecular clouds. We averaged all spatial positions away from known outflows near seven protostars. We find significant agreement with predictions of models of turbulent dissipation in slightly denser (10$^{3.5}$ cm$^{-3}$) material with a stronger magnetic field (24 $\mu$G) than in the general molecular cloud.

Imaging the cold molecular gas in SDSS J1148 + 5251 at z = 6.4

We present Karl G. Jansky Very Large Array (VLA) observations of the CO (J = 2 → 1) line emission towards the z = 6.419 quasar SDSS J114816.64 + 525150.3 (J1148 + 5251). The molecular gas is found to be marginally resolved with a major axis of 0.9 arcsec (consistent with previous size measurements of the CO (J = 7 → 6) emission). We observe tentative evidence for extended line emission towards the south-west on a scale of ∼1.4 arcsec, but this is only detected at 3.3σ significance and should be confirmed. The position of the molecular emission region is in excellent agreement with previous detections of low-frequency radio continuum emission as well as [C ii] line and thermal dust continuum emission. These CO (J = 2 → 1) observations provide an anchor for the low-excitation part of the molecular line spectral energy distribution. We find no evidence for extended low-excitation component, neither in the spectral line energy distribution nor the image. We fit a single kinetic gas temperature model of 50 K. We revisit the gas and dynamical masses in light of this new detection of a low-order transition of CO, and confirm previous findings that there is no extended reservoir of cold molecular gas in J1148 + 5251, and that the source departs substantially from the low-z relationship between black hole mass and bulge mass. Hence, the characteristics of J1148 + 5251 at z = 6.419 are very similar to z ∼ 2 quasars, in the lack of a diffuse cold gas reservoir and kpc-size compactness of the star-forming region.

OBSERVATIONS OF TYPE Ia SUPERNOVA 2014J WITH FLITECAM ON SOFIA

We present medium resolution near-infrared (NIR) spectra, covering 1.1 to 3.4 microns, of the normal Type Ia supernova (SN Ia) SN 2014J in M82 obtained with the FLITECAM instrument aboard SOFIA approximately 17-25 days after maximum B light. Our 2.8-3.4 micron spectra may be the first ~3 micron spectra of a SN Ia ever published. The spectra spanning the 1.5-2.7 micron range are characterized by a strong emission feature at ~1.77 microns with a full width at half maximum of ~11,000-13,000 km/s. We compare the observed FLITECAM spectra to the recent non-LTE delayed detonation models of Dessart et al. (2014) and find that the models agree with the spectra remarkably well in the 1.5-2.7 micron wavelength range. Based on this comparison we identify the ~1.77 micron emission peak as a blend of permitted lines of Co II. Other features seen in the 2.0 - 2.5 micron spectra are also identified as emission from permitted transitions of Co II. However, the models are not as successful at reproducing the spectra in the 1.1 - 1.4 micron range or between 2.8 and 3.4 microns. These observations demonstrate the promise of SOFIA by allowing access to wavelength regions inaccessible from the ground, and serve to draw attention to the usefulness of the regions between the standard ground-based NIR passbands for constraining SN models.

Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

To extend the molecular gas measurements to typical star-forming galaxies (SFGs) with SFR < 40 Msun yr^{-1} and M* < 2.5x10^{10} Msun at z~1.5-3, we have observed CO emission with the IRAM Plateau de Bure Interferometer and 30m telescope for five strongly-lensed galaxies selected from the Herschel Lensing Survey. These observations are combined with a compilation of CO measurements from the literature. We infer the luminosity correction factors r2,1 = 0.81+/-0.20 and r3,1 = 0.57+/-0.15 for the J=2 and J=3 CO transitions, respectively, valid for SFGs at z>1. The combined sample of CO-detected SFGs at z>1 shows a large spread in star formation efficiency (SFE), such that SFE extend beyond the low values of local spirals and overlap the distribution of z>1 sub-mm galaxies. We find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to primarily the specific star formation rate, but also stellar mass and redshift. Correlations of SFE with the offset from the main-sequence and the compactness of the starburst are less clear. The increase of the molecular gas depletion timescale with M* now revealed by low M* SFGs at z>1 and observed at z=0 is in contrast to the admitted constant molecular gas depletion timescale and the linear Kennicutt-Schmidt relation. We confirm an increase of the molecular gas fraction (fgas) from z~0.2 to z~1.2, followed by a very mild increase toward higher redshifts. At each redshift fgas shows a large dispersion due to the dependence of fgas on M*, producing a gradient of increasing fgas with decreasing M*. We provide the first measure of fgas of z>1 SFGs at the low-M* end (10^{9.4} < M*/Msun < 10^{9.9}), reaching a mean fgas = 0.69+/-0.18, which shows a clear fgas upturn. Finally, we find evidence for a non-universal dust-to-gas ratio among high-redshift SFGs and sub-mm galaxies, local spirals and ULIRGs with near-solar metallicities.

Electron Magnetic Resonance Studies of Nanosized Nd0.65Ca0.35 Mn1−xCrxO3 (x = 0, 0.06, 0.1) Manganite

We report a systematic investigation of the temperature dependence of electron magnetic resonance (EMR) line width, intensity and resonance field for ~25 nm Nd0.65Ca0.35MnO3 (NCMO1), Nd0.65Ca0.35Mn0.94Cr0.06O3 (NCMO2) and Nd0.65Ca0.35Mn0.9Cr0.1O3 (NCMO3) nanoparticles prepared by sol–gel method. The EMR line widths for the three nano-samples differ significantly from one another below a temperature T min where the line width has a minimum. T min was found to be 130, 100 and 120 K for NCMO1, NCMO2 and NCMO3, respectively. Well above T min the line width values for the three samples are close to one another. The sharp upturn of EMR line width below T min is attributed to the formation of short range, ferromagnetically ordered clusters. Temperature dependence of EMR intensity shows a residual CO transition in NCMO1 and NCMO2 and a complete disappearance of it in NCMO3. The intensity undergoes significant increase below 120, 80 and 100 K for NCMO1, NCMO2 and NCMO3, respectively, indicating the onset of ferromagnetic transitions. The occurrence of ferromagnetic transition is further confirmed by magnetization hysteresis measurements. The decrease in T C in NCMO2 and NCMO3 compared to NCMO1 nanoparticles is understood to be due to the destruction of the double-exchange interaction by chromium doping. The resonance field decreases below the ferromagnetic onset temperatures for all the samples as expected. The combined effects of the reduction in size and of chromium doping in Mn site are discussed.

ASSESSING MOLECULAR OUTFLOWS AND TURBULENCE IN THE PROTOSTELLAR CLUSTER SERPENS SOUTH

Molecular outflows driven by protostellar cluster members likely impact their surroundings and contribute to turbulence, affecting subsequent star formation. The very young Serpens South cluster consists of a particularly high density and fraction of protostars, yielding a relevant case study for protostellar outflows and their impact on the cluster environment. We combined CO $J=1-0$ observations of this region using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Institut de Radioastronomie Millim\'{e}trique (IRAM) 30 m single dish telescope. The combined map allows us to probe CO outflows within the central, most active region at size scales of 0.01 pc to 0.8 pc. We account for effects of line opacity and excitation temperature variations by incorporating $^{12}$CO and $^{13}$CO data for the $J=1-0$ and $J=3-2$ transitions (using Atacama Pathfinder Experiment and Caltech Submillimeter Observatory observations for the higher CO transitions), and we calculate mass, momentum, and energy of the molecular outflows in this region. The outflow mass loss rate, force, and luminosity, compared with diagnostics of turbulence and gravity, suggest that outflows drive a sufficient amount of energy to sustain turbulence, but not enough energy to substantially counter the gravitational potential energy and disrupt the clump. Further, we compare Serpens South with the slightly more evolved cluster NGC 1333, and we propose an empirical scenario for outflow-cluster interaction at different evolutionary stages.

Submillimeter mapping of mesospheric minor species on Venus with ALMA

Millimeter and submillimeter heterodyne spectroscopy offers the possibility of probing the mesosphere of Venus and monitoring minor species and winds. ALMA presents a unique opportunity to map mesospheric species of Venus. During Cycle 0, we have observed Venus on November 14 and 15, 2011, using the compact configuration of ALMA. The diameter of Venus was 11″ and the illumination factor was about 90%. Maps of CO, SO, SO2 and HDO have been built from transitions recorded in the 335–347GHz frequency range. A mean mesospheric thermal profile has been inferred from the analysis of the CO transition at the disk center, to be used in support of minor species retrieval. Maps of SO and SO2 abundance show significant local variations over the disk and contrast variations by as much as a factor 4. In the case of SO2, the spatial distribution appears more “patchy”, i.e. shows short-scale structures apparently disconnected from day-side and latitudinal variations. For both molecules, significant changes occur over a timescale of one day. From the disk averaged spectrum of SO recorded on November 14 at 346.528GHz, we find that the best fit is obtained with a cutoff in the SO vertical distribution at 88±2km and a uniform mixing ratio of 8.0±2.0ppb above this level. The SO2 map of November 14, derived from the weaker transition at 346.652GHz, shows a clear maximum in the morning side at low latitudes, which is less visible in the map of November 15. We find that the best fit for SO2 is obtained for a cutoff in the vertical distribution at 88±3km and a uniform mixing ratio of 12.0±3.5ppb above this level. The HDO maps retrieved from the 335.395GHz show some enhancement in the northern hemisphere, but less contrasted variations than for the sulfur species maps, with little change between November 14 and 15. Assuming a typical D/H ratio of 200 times the terrestrial value in the mesosphere of Venus, we find that the disk averaged HDO spectrum is best fitted with a uniform H2O mixing ratio of 2.5±0.6ppm (corresponding to a HDO mixing ratio of 0.165±0.040ppm). We note that our spectrum is also compatible with a H2O mixing ratio of 1.5ppm in the 80–90km altitude range, and a mixing ratio of 3ppm outside this range, as suggested by the photochemical model of Zhang et al. (2012, Icarus, vol. 217, pp. 714–739). Our results are in good general agreement with previous single dish submillimeter observations of Sandor and Clancy (2005, Icarus, vol. 177, pp. 129–143), Gurwell et al. (2007, Icarus, vol. 188, p. 288), and Sandor et al. (2010, Icarus, vol. 208, pp. 49–60; 2012, Icarus, vol. 217, pp. 839–844 ) and with SPICAV/Venus Express results of Fedorova et al. (2008, J. Geophys. Res., vol. 113, p. E00B25) and Belyaev et al. (2012).

THEHERSCHELCOMPREHENSIVE (U)LIRG EMISSION SURVEY (HERCULES): CO LADDERS, FINE STRUCTURE LINES, AND NEUTRAL GAS COOLING

(Ultra) Luminous Infrared Galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8-1000 $\mu$m) luminosities ($L_{LIRG}>10^{11} $L$_\odot$ and $L_{ULIRG}>10^{12}$ L$_\odot$). The Herschel Comprehensive ULIRG Emission Survey (HerCULES; PI van der Werf) presents a representative flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of these objects (10$^{11}\leq L_\odot \geq10^{13}$). With the \emph{Herschel Space Observatory}, we observe [CII] 157 $\mu$m, [OI] 63 $\mu$m, and [OI] 145 $\mu$m line emission with PACS, CO J=4-3 through J=13-12, [CI] 370 $\mu$m, and [CI] 609 $\mu$m with SPIRE, and low-J CO transitions with ground-based telescopes. The CO ladders of the sample are separated into three classes based on their excitation level. In 13 of the galaxies, the [OI] 63 $\mu$m emission line is self absorbed. Comparing the CO excitation to the IRAS 60/100 $\mu$m ratio and to far infrared luminosity, we find that the CO excitation is more correlated to the far infrared colors. We present cooling budgets for the galaxies and find fine-structure line flux deficits in the [CII], [SiII], [OI], and [CI] lines in the objects with the highest far IR fluxes, but do not observe this for CO $4\leq J_{upp}\leq13$. In order to study the heating of the molecular gas, we present a combination of three diagnostic quantities to help determine the dominant heating source. Using the CO excitation, the CO J=1-0 linewidth, and the AGN contribution, we conclude that galaxies with large CO linewidths always have high-excitation CO ladders, and often low AGN contributions, suggesting that mechanical heating is important.

Magnetocrystalline anisotropic effect inGdCo1−xFexAsO(x=0,0.05)

From a systematic study of the electrical resistivity $\rho(T,H)$, magnetic susceptibility $\chi(T,H)$, isothermal magnetization $M(H)$ and the specific heat $C(T,H)$, a temperature-magnetic field ($T$-$H$) phase diagram has been established for GdCo$_{1-x}$Fe$_x$AsO ($x = 0$ and $0.05$) polycrystalline compounds. GdCoAsO undergoes two long-range magnetic transitions: ferromagnetic (FM) transition of Co $3d$ electrons ($T_\textup{C}^\textup{Co}$) and antiferromagnetic (AFM) transition of Gd $4f$ electrons ($T_\textup{N}^\textup{Gd}$). For the Fe-doped sample ($x=0.05$), an extra magnetic reorientation transition takes place below $T_\textup{N}^\textup{Gd}$, which is likely associated with Co moments. The two magnetic species of Gd and Co are coupled antiferromagnetically to give rise to ferrimagnetic (FIM) behavior in the magnetic susceptibility. Upon decreasing the temperature ($T < T_\textup{C}^\textup{Co}$), the magnetocrystalline anisotropy breaks up the FM order of Co by aligning the moments with the local easy axes of the various grains, leading to a spin reorientation transition at $T_\textup{R}^\textup{Co}$. By applying a magnetic field, $T_\textup{R}^\textup{Co}$ monotonically decreases to lower temperatures, while the $T_\textup{N}^\textup{Gd}$ is relatively robust against the external field. On the other hand, the applied magnetic field pulls the magnetization of grains from the local easy direction to the field direction via a first-order reorientation transition, with the transition field ($H_\textup{M}$) increasing upon cooling the temperature.

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion.

Gas clouds in present-day galaxies are inefficient at forming stars. Low star-formation efficiency is a critical parameter in galaxy evolution: it is why stars are still forming nearly 14billion years after the Big Bang and why star clusters generally do not survive their births, instead dispersing to form galactic disks or bulges. Yet the existence of ancient massive bound star clusters (globular clusters) in the Milky Way suggests that efficiencies were higher when they formed ten billion years ago. A local dwarf galaxy, NGC5253, has a young star cluster that provides an example of highly efficient star formation. Here we report the detection of the J = 3→2 rotational transition of CO at the location of the massive cluster. The gas cloud is hot, dense, quiescent and extremely dusty. Its gas-to-dust ratio is lower than the Galactic value, which we attribute to dust enrichment by the embedded star cluster. Its star-formation efficiency exceeds 50 per cent, tenfold that of clouds in the Milky Way. We suggest that high efficiency results from the force-feeding of star formation by a streamer of gas falling into the galaxy.

Spontaneously formed interfacial metal silicates and their effect on the magnetism of superparamagnetic FeCo/SiO₂ core/shell nanoparticles.

The integration of superparamagnetic core/shell nanoparticles into devices and other nanoscale technological applications requires a detailed understanding of how the intimate contact between core and shell nanophases affects the magnetism. We report how, for single-domain FeCo nanoparticles, an FeCo phase unique to the nanoscale with silica shells of increasing thicknesses spontaneously formed interfacial metal silicates between the core and shell (such as Fe2SiO4 and Co2SiO4) and altered the overall magnetism of the nanomaterial significantly. The influence of this previously overlooked phenomenon on magnetic properties is reported. Evidence of these metal silicate interfacial layers was observed by X-ray absorption spectroscopy (XAS) collected over the L3,2 absorption edges of Fe and X-ray photoelectron spectra (XPS) collected over the 2p transitions of Fe and Co. Through the correlation of magnetometry and XPS data, the evolution of nanoparticle magnetic anisotropy is shown to increase with the metal silicate.