- ID:
- ivo://CDS.VizieR/J/ApJ/862/110
- Title:
- Metallicity measurements in 70 nearby galaxies
- Short Name:
- J/ApJ/862/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the metallicity dependence of HI surface densities in star-forming regions along many lines of sight within 70 nearby galaxies, probing kiloparsec to 50pc scales. We employ HI, SFR, stellar mass, and metallicity (gradient) measurements from the literature, spanning a wide range (5dex) in stellar and gas mass and (1.6dex) in metallicity. We consider metallicities as observed, or rescaled to match the mass-metallicity relation determined for SDSS galaxies. At intermediate to high metallicities (0.3-2 times solar), we find that the HI surface densities saturate at sufficiently large total gas surface density. The maximal HI columns vary approximately inversely with metallicity, and show little variation with spatial resolution, galactocentric radius, or among galaxies. In the central parts of massive spiral galaxies, the HI gas is depressed by factors of ~2. The observed behavior is naturally reproduced by metallicity dependent shielding theories for the HI-to-H2 transitions in star-forming galaxies. We show that the inverse scaling of the maximal HI columns with metallicity suggests that the area filling fraction of atomic-molecular complexes in galaxies is of the order of unity, and weakly dependent on metallicity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/854/170
- Title:
- Methanol (CH_3_OH) and OH masers in NGC 6334I
- Short Name:
- J/ApJ/854/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first sub-arcsecond VLA imaging of 6GHz continuum, methanol maser, and excited-state hydroxyl maser emission toward the massive protostellar cluster NGC 6334I following the recent 2015 outburst in (sub)millimeter continuum toward MM1, the strongest (sub)millimeter source in the protocluster. In addition to detections toward the previously known 6.7GHz Class II methanol maser sites in the hot core MM2 and the UCHII region MM3 (NGC 6334F), we find new maser features toward several components of MM1, along with weaker features ~1" north, west, and southwest of MM1, and toward the nonthermal radio continuum source CM2. None of these areas have heretofore exhibited Class II methanol maser emission in three decades of observations. The strongest MM1 masers trace a dust cavity, while no masers are seen toward the strongest dust sources MM1A, 1B, and 1D. The locations of the masers are consistent with a combination of increased radiative pumping due to elevated dust grain temperature following the outburst, the presence of infrared photon propagation cavities, and the presence of high methanol column densities as indicated by ALMA images of thermal transitions. The nonthermal radio emission source CM2 (2" north of MM1) also exhibits new maser emission from the excited 6.035 and 6.030GHz OH lines. Using the Zeeman effect, we measure a line-of-sight magnetic field of +0.5 to +3.7mG toward CM2. In agreement with previous studies, we also detect numerous methanol and excited OH maser spots toward the UCHII region MM3, with predominantly negative line-of-sight magnetic field strengths of -2 to -5mG and an intriguing south-north field reversal.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/566
- Title:
- Methanol maser associated outflows
- Short Name:
- J/MNRAS/444/566
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected the positions of 54 6.7GHz methanol masers from the Methanol Multibeam Survey catalogue, covering a range of longitudes between 20{deg} and 34{deg} of the Galactic plane. These positions were mapped in the J=3-2 transition of both the ^13^CO and C^18^O lines. A total of 58 ^13^CO emission peaks are found in the vicinity of these maser positions. We search for outflows around all ^13^CO peaks, and find evidence for high-velocity gas in all cases, spatially resolving the red and blue outflow lobes in 55 cases. Of these sources, 44 have resolved kinematic distances, and are closely associated with the 6.7GHz masers, a subset referred to as Methanol Maser Associated Outflows (MMAOs). We calculate the masses of the clumps associated with each peak using 870{mu}m continuum emission from the ATLASGAL survey. A strong correlation is seen between the clump mass and both outflow mass and mechanical force, lending support to models in which accretion is strongly linked to outflow. We find that the scaling law between outflow activity and clump masses observed for low-mass objects, is also followed by the MMAOs in this study, indicating a commonality in the formation processes of low-mass and high-mass stars.
404. M31 Herschel images
- ID:
- ivo://CDS.VizieR/J/A+A/567/A71
- Title:
- M31 Herschel images
- Short Name:
- J/A+A/567/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust and stars play a complex game of interactions in the interstellar medium and around young stars. The imprints of these processes are visible in scaling relations between stellar characteristics, star formation parameters, and dust properties. Aims. In the present work, we aim to examine dust scaling relations on a sub-kpc resolution in the Andromeda galaxy (M31). The goal is to investigate the properties of M31 on both a global and local scale and compare them to other galaxies of the local universe. Methods. New Herschel observations are combined with available data from GALEX, SDSS, WISE, and Spitzer to construct a dataset covering UV to submm wavelengths. All images were brought to the beam size and pixel grid of the SPIRE 500um frame. This divides M31 in 22437 pixels of 36 arcseconds in size on the sky, corresponding to physical regions of 137x608pc in the galaxy's disk. A panchromatic spectral energy distribution was modelled for each pixel and maps of the physical quantities were constructed. Several scaling relations were investigated, focussing on the interactions of dust with starlight. Results. We find, on a sub-kpc scale, strong correlations between Mdust/M* and NUV-r, and between Mdust/M* and mu* (the stellar mass surface density). Striking similarities with corresponding relations based on integrated galaxies are found. We decompose M31 in four macro-regions based on their FIR morphology; the bulge, inner disk, star forming ring, and the outer disk region. In the scaling relations, all regions closely follow the galaxy-scale average trends and behave like galaxies of different morphological types. The specific star formation characteristics we derive for these macro-regions give strong hints of an inside-out formation of the bulge-disk geometry, as well as an internal downsizing process. Within each macro-region, however, a great diversity in individual micro-regions is found, regardless of the properties of the macro-regions. Furthermore, we confirm that dust in the bulge of M31 is heated only by the old stellar populations. Conclusions. In general, the local dust scaling relations indicate that the dust content in M31 is maintained by a subtle interplay of past and present star formation. The similarity with galaxy-based relations strongly suggests that they are in situ correlations, with underlying processes that must be local in nature.
405. MHO Catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/511/A24
- Title:
- MHO Catalogue
- Short Name:
- J/A+A/511/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of Molecular Hydrogen emission-line Objects (MHOs) in outflows from young stars, most of which are deeply embedded. All objects are identified in the near-infrared lines of molecular hydrogen, all reside in the Milky Way, and all are associated with jets or molecular outflows. Objects in both low and high-mass star forming regions are included. This catalogue complements the existing database of Herbig-Haro objects; indeed, for completeness, HH objects that are detected in H_2_ emission are included in the MHO catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A16
- Title:
- M43, Horsehead, MonR2, M17SW [CII]158um spectra
- Short Name:
- J/A+A/636/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The [CII] 158um FIR fine-structure line is one of the most important cooling lines of the star-forming ISM. It is used as a tracer of star formation efficiency in external galaxies and to study feedback effects in parental clouds. High spectral resolution observations have shown complex structures in the line profiles of the [CII] emission. To determine whether the complex profiles observed in [^12^CII] are due to individual velocity components along the line-of-sight or due to self-absorption, one has to compare the [^12^CII] and isotopic [^13^CII] line profiles. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in the sources M43, Horsehead PDR, Monoceros R2 and M17 SW allow to detect with high S/N the optically thin [^13^CII] and simultaneously the [^12^CII] emission lines. We first derive the [^12^CII] optical depth and the [CII] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows to derive the physical conditions of the [CII] gas: column density and excitation temperature. We find moderate to high [^12^CII] optical depths in all four sources, and self-absorption of [^12^CII] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41mag. The foreground absorption requires substantial column densities of cold and dense [CII] gas, with an equivalent Av ranging up to about 13mag. The column density of the warm background material requires multiple PDR surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [CII] gas detected in absorption cannot be explained with any known scenario and we can only speculate about its origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/38
- Title:
- MHOs toward 22 regions with H2 fluxes
- Short Name:
- J/ApJ/844/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a narrow-band near-infrared imaging survey for Molecular Hydrogen emission-line Objects (MHOs) toward 26 regions containing high-mass protostellar candidates and massive molecular outflows. We have detected a total of 236 MHOs, 156 of which are new detections, in 22 out of the 26 regions. We use H_2_2.12{mu}m/H_2_2.25{mu}m flux ratios, together with morphology, to separate the signatures of fluorescence associated with photo- dissociation regions (PDRs) from shocks associated with outflows in order to identify the MHOs. PDRs have typical low flux ratios of ~1.5-3, while the vast majority of MHOs display flux ratios typical of C-type shocks (~6-20). A few MHOs exhibit flux ratios consistent with expected values for J-type shocks (~3-4), but these are located in regions that may be contaminated with fluorescent emission. Some previously reported MHOs have low flux ratios, and are likely parts of PDRs rather than shocks indicative of outflows. We identify a total of 36 outflows across the 22 target regions where MHOs were detected. In over half these regions, MHO arrangements and fluorescent structures trace features present in CO outflow maps, suggesting that the CO emission traces a combination of dynamical effects, which may include gas entrained in expanding PDRs as well as bipolar outflows. Where possible, we link MHO complexes to distinct outflows and identify candidate driving sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/630/381
- Title:
- Mid-IR imaging in {rho} Oph
- Short Name:
- J/ApJ/630/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a comprehensive, new, ground-based mid-infrared imaging survey of the young stellar population of the {rho} Ophiuchi cloud are presented. Data were acquired at the Palomar 5m and at the Keck 10m telescopes with the MIRLIN (Mid-InfraRed Large-well Imager) and LWS (Long Wavelength Spectrometer centered at 12.5{mu}m) instruments, at 0.5" and 0.25" resolutions, respectively. Of 172 survey objects, 85 were detected. Among the 22 multiple systems observed, 15 were resolved and their individual component fluxes determined.
- ID:
- ivo://CDS.VizieR/J/ApJ/719/1191
- Title:
- Mid-IR indicators of SF and AGN in galaxies
- Short Name:
- J/ApJ/719/1191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z~0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS), which includes multi-wavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to ~30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [NeII]12.8um/[OIV]25.9um line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs.
- ID:
- ivo://CDS.VizieR/J/AJ/129/1534
- Title:
- Mid-IR photometry in the Orion Nebula
- Short Name:
- J/AJ/129/1534
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two wide-field (~5'x3.5'), diffraction-limited ({lambda}/D~0.5" at 10{mu}m), broadband 10 and 20{mu}m images of the Orion Nebula, plus six 7-13{mu}m narrowband images of the BN/KL complex taken at the 3.8m UKIRT telescope with the MPIA MAX camera.
