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We present the highest-resolution (1″) 12CO observations of molecular gas in the dwarf starburst galaxy NGC 625 to date, obtained with Atacama Large Millimeter/submillimeter Array. The molecular gas, which is distributed in discrete clouds within an area of 0.4 kpc2, does not have well-ordered large-scale motions. We measure a molecular mass in NGC 625 of 5.3 × 106 , assuming a Milky Way CO-to- conversion factor. We use the CPROPS package to identify molecular clouds and measure their properties. The 19 resolved CO clouds have a median radius of 20 pc, a median linewidth 2.5 , and a median surface density of 169. Larson scaling relations suggest that molecular clouds in NGC 625 are mostly in virial equilibrium. Comparison of our high-resolution CO observations with a star formation rate map, inferred from ancillary optical observations, suggests that about 40% of the molecular clouds coincide with the brightest H ii regions. These bright H ii regions have a range of molecular gas depletion timescales, all within a factor of ∼3 of the global depletion time in NGC 625 of 106–134 Myr. The highest surface density molecular clouds toward the southwest of the galaxy, in a region we call the Butterfly, do not show strong star formation activity and suggest a depletion timescale longer than 5 Gyr. [ABSTRACT FROM AUTHOR]

Context. Cloud-scale surveys of molecular gas reveal the link between giant molecular cloud properties and star formation across a range of galactic environments. Cloud populations in galaxy disks are considered to be representative of the normal star formation process, while galaxy centers tend to harbor denser gas that exhibits more extreme star formation. At high resolution, however, molecular clouds with exceptional gas properties and star formation activity may also be observed in normal disk environments. In this paper we study the brightest cloud traced in CO(2–1) emission in the disk of nearby spiral galaxy NGC 628. Aims. We characterize the properties of the molecular and ionized gas that is spatially coincident with an extremely bright H II region in the context of the NGC 628 galactic environment. We investigate how feedback and large-scale processes influence the properties of the molecular gas in this region. Methods. High-resolution ALMA observations of CO(2–1) and CO(1−0) emission were used to characterize the mass and dynamical state of the "headlight" molecular cloud. The characteristics of this cloud are compared to the typical properties of molecular clouds in NGC 628. A simple large velocity gradient (LVG) analysis incorporating additional ALMA observations of 13CO(1−0), HCO+(1−0), and HCN(1−0) emission was used to constrain the beam-diluted density and temperature of the molecular gas. We analyzed the MUSE spectrum using Starburst99 to characterize the young stellar population associated with the H II region. Results. The unusually bright headlight cloud is massive (1 − 2 × 107 M⊙), with a beam-diluted density of nH2 = 5 × 104 cm−3 based on LVG modeling. It has a low virial parameter, suggesting that the CO emission associated with this cloud may be overluminous due to heating by the H II region. A young (2 − 4 Myr) stellar population with mass 3 × 105 M⊙ is associated. Conclusions. We argue that the headlight cloud is currently being destroyed by feedback from young massive stars. Due to the large mass of the cloud, this phase of the its evolution is long enough for the impact of feedback on the excitation of the gas to be observed. The high mass of the headlight cloud may be related to its location at a spiral co-rotation radius, where gas experiences reduced galactic shear compared to other regions of the disk and receives a sustained inflow of gas that can promote the mass growth of the cloud. [ABSTRACT FROM AUTHOR]

This review describes where we are today in light of the dust and gas properties and their relation to star formation, in low metallicity galaxies of the local universe following recent surveys from sensitive infrared space telescopes, mainly Spitzer and Herschel space observatories as well as ground-based observations of the molecular gas reservoir. Models to interpret the ISM properties are gaining sophistication in order to account for the wide range of valuable observational diagnostics that we have today to trace the different gas phases, the broad range of photometry we have, from mid-infrared to submillimetre dust emission and the various galactic size scales that we can sample today. This review summarizes the rich multi-phase observations we can exploit today, and the multi-phase modeling approach to interpret the observations. [ABSTRACT FROM AUTHOR]

We present a method to simultaneously model the dust far-infrared (FIR) spectral energy distribution (SED) and the total infrared - carbon monoxide (CO) integrated intensity (SIR-ICO) relationship. The modelling employs a hierarchical Bayesian (HB) technique to estimate the dust surface density, temperature (Teff), and spectral index at each pixel from the observed FIR maps. Additionally, given the corresponding CO map, the method simultaneously estimates the slope and intercept between the FIR and CO intensities, which are global properties of the observed source. The model accounts for correlated and uncorrelated uncertainties, such as those present in Herschel observations. Using synthetic data sets, we demonstrate the accuracy of the HB method, and contrast the results with common non-hierarchical fitting methods. As an initial application, we model the dust and gas on 100 pc scales in the Magellanic Clouds from Herschel FIR and NANTEN CO observations. The slopes of the logSIR-logICO relationship are similar in both galaxies, falling in the range 1.1-1.7. However, in the Small Magellanic Cloud the intercept is nearly three times higher, which can be explained by its lower metallicity than the Large Magellanic Cloud (LMC), resulting in a larger SIR per unit ICO. The HB modelling evidences an increase in Teff in regions with the highest ICO in the LMC. This may be due to enhanced dust heating in the densest molecular regions from young stars. Such simultaneous dust and gas modelling may reveal variations in the properties of the interstellar medium and its association with other galactic characteristics, such as star formation rates and/or metallicities. [ABSTRACT FROM AUTHOR]

Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC 147, NGC 185, and NGC 205) of the Andromeda galaxy are characterized by very different interstellar medium properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC 205 has been studied in detail in an earlier work, we present new Herschel dust continuum observations of NGC 147 and NGC 185. The non-detection of NGC 147 in Herschel SPIRE maps puts a strong constraint on its dust mass (≤128-68+124 M⊙). For NGC 185, we derive a total dust mass Md = 5.1±1.0 × 10³ M⊙, which is a factor of ~2-3 higher than that derived from ISO and Spitzer observations and confirms the need for longer wavelength observations to trace more massive cold dust reservoirs. We, furthermore, estimate the dust production by asymptotic giant branch (AGB) stars and supernovae (SNe). For NGC 147, the upper limit on the dust mass is consistent with expectations of the material injected by the evolved stellar population. In NGC 185 and NGC 205, the observed dust content is one order of magnitude higher compared to the estimated dust production by AGBs and SNe. Efficient grain growth, and potentially longer dust survival times (3-6 Gyr) are required to account for their current dust content. Our study confirms the importance of grain growth in the gas phase to account for the current dust reservoir in galaxies. [ABSTRACT FROM AUTHOR]

As part of the Bluedisk survey, we analyse the radial gas-phase metallicity profiles of 50 late-type galaxies. We compare the metallicity profiles of a sample of HI-rich galaxies against a control sample of HI-'normal' galaxies. We find the metallicity gradient of a galaxy to be strongly correlated with its HI mass fraction (M(HI)/M*).We note that some galaxies exhibit a steeper metallicity profile in the outer disc than in the inner disc. These galaxies are found in both the HI-rich and control samples. This contradicts a previous indication that these outer drops are exclusive to HI-rich galaxies. These effects are not driven by bars, although we do find some indication that barred galaxies have flatter metallicity profiles. By applying a simple analytical model, we are able to account for the variety of metallicity profiles that the two samples present. The success of this model implies that the metallicity in these isolated galaxies may be in a local equilibrium, regulated by star formation. This insight could provide an explanation of the observed local mass-metallicity relation. [ABSTRACT FROM AUTHOR]

We present Atacama Large (sub)Millimeter Array observations of 30 Doradus-the highest resolution view of molecular gas in an extragalactic star formation region to date (~0.4 pc × 0.6 pc). The 30Dor-10 cloud north of R136 was mapped in 12CO 2-1, 13CO 2-1, C18O 2-1, 1.3 mm continuum, the H30α recombination line, and two H2CO 3-2 transitions. Most 12CO emission is associated with small filaments and clumps (≲1 pc, ~103 Mʘ at the current resolution). Some clumps are associated with protostars, including "pillars of creation" photoablated by intense radiation from R136. Emission from molecular clouds is often analyzed by decomposition into approximately beam-sized clumps. Such clumps in 30 Doradus follow similar trends in size, linewidth, and surface density to MilkyWay clumps. The 30 Doradus clumps have somewhat larger linewidths for a given size than predicted by Larson's scaling relation, consistent with pressure confinement. They extend to a higher surface density at a given size and linewidth compared to clouds studied at 10 pc resolution. These trends are also true of clumps in Galactic infrared-dark clouds; higher resolution observations of both environments are required. Consistency of clump masses calculated from dust continuum, CO, and the virial theorem reveals that the CO abundance in 30 Doradus clumps is not significantly different from the Large Magellanic Cloud mean, but the dust abundance may be reduced by ~2. There are no strong trends in clump properties with distance from R136; dense clumps are not strongly affected by the external radiation field, but there is a modest trend toward lower dense clump filling fraction deeper in the cloud. [ABSTRACT FROM AUTHOR]

We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from Jup = 4 to 12, as well as the two [CI] fine structure lines at 492 and 809 GHz and the [NII]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (nH2 ~ 103.2-103.9 cm-3 and Tkin ~ 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H2 emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C i] emission suggests that it is produced in cold (Tkin < 30 K) and dense (nH2 > 103 cm-3) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H2O emission lines are present. Additionally, three OH+ lines at 909, 971, and 1033 GHz are identified in NGC 7130. [ABSTRACT FROM AUTHOR]

The wide variety of low metallicity galaxies of the local universe serve as convenient laboratories to study the evolution of gas and dust and conditions for star formation in environments which may resemble those of the early universe. The Herschel Dwarf Galaxy Survey is studying the far infrared (FIR) and submillimeter (submm) properties of the gas and dust in galaxies with metallicity values as low as 1/45 that of solar. With complementary Spitzer, Laboca/APEX, Scuba/JCMT data, the dust spectral energy distributions are well constrained now, providing more accurate dust masses. We find a steep drop in dust-to-gas mass ratio (D/G) when the metallicity is below 12+log(O/H) ∼ 8. A submillimeter excess can be found in some low metallicity galaxies, which, when present, becomes apparent at wavelengths at or longer than 500 μm. While CO is difficult to observe in low metallicity gas, the FIR fine structure lines, on the other hand, are very luminous and highlight a potentially important reservoir of CO-free molecular gas, better traced by the 158 μm [CII] line. [ABSTRACT FROM PUBLISHER]

The low metallicity interstellar medium of dwarf galaxies gives a different picture in the far infrared(FIR)/submillimetre(submm)wavelengths than the more metal-rich galaxies. Excess emission is often found in the submm beginning at or beyond 500 μm. Even without taking this excess emission into account as a possible dust component, higher dust-to-gas mass ratios (DGR) are often observed compared to that expected from their metallicity for moderately metal-poor galaxies. The Spectral Energy Distributions (SEDs) of the lowest metallicity galaxies, however, give very low dust masses and excessively low values of DGR, inconsistent with the amount of metals expected to be captured into dust if we presume the usual linear relationship holding for all metallicities, including the more metal-rich galaxies. This transition seems to appear near metalllicities of 12 + log(O/H) 8.0 - 8.2. These results rely on accurately quantifying the total molecular gas reservoir, which is uncertain in low metallicity galaxies due to the difficulty in detecting CO(1-0) emission. Dwarf galaxies show an exceptionally high [CII] 158 μm/CO (1-0) ratio which may be indicative of a significant reservoir of ‘CO-free’ molecular gas residing in the photodissociated envelope, and not traced by the small CO cores. [ABSTRACT FROM PUBLISHER]

In order to use supernovae (SNe) as cosmological probes, a good understanding of their properties and diversity is necessary. Here we investigate whether principal component analysis (PCA) can be used to improve the calibration of Type Ia SNe. We apply PCA to two different cases: a small data set of supernova spectra taken at maximum light and a larger data set with more spectra taken at various epochs. On the SN Ia luminosity scale, the supernova SN 1991T appears at the upper end and SN 1991bg at the lower end. While 91bg-like SNe seem to form a distinct group, 91T-like SNe show a continuum of properties with normal SNe. The differences are mainly explained by line shifts in the spectra. However, we do not find that PCA is able to distinguish trends or subsets in the supernova data beyond what has already been found using specific spectral features. The main utility of PCA will be as a tool for characterizing large sets of spectra. We show how the information in a data base of supernova spectra can be vastly simplified using PCA. This can be used to make a continuum of spectral templates from a discrete library of spectra, which may be useful in k-corrections and the training of supernova light-curve fitters. [ABSTRACT FROM AUTHOR]

The article presents a study on analytical approaches for development and validation of Beryllium (Be) in a biological matrix. The study analyzes samples from volunteers who have not been exposed to Be, as well as livers and kidneys brought from a distributor using a Perkin Elmer Elan DRC-II and a quartz nebulizer. Results of powder dissolution test reveal a major difference between the initial values and final analysis sequence in the matrix prior to the application of a correction method.