- ID:
- ivo://CDS.VizieR/J/A+A/608/A127
- Title:
- Breaks in disc galaxy abundance gradients
- Short Name:
- J/A+A/608/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the relation between breaks in the surface brightness profiles and radial abundance gradients within the optical radius in the discs of 134 spiral galaxies from the CALIFA survey. The distribution of the radial abundance (in logarithmic scale) in each galaxy was fitted by simple and broken linear relations. The surface brightness profile was fitted assuming pure and broken exponents for the disc. We find that the maximum absolute difference between the abundances in a disc given by broken and pure linear relations is less than 0.05dex in the majority of our galaxies and exceeds the scatter in abundances for 26 out of 134 galaxies considered. The scatter in abundances around the broken linear relation is close (within a few percent) to that around the pure linear relation. The breaks in the surface brightness profiles are more prominent. The scatter around the broken exponent in a number of galaxies is lower by a factor of two or more than that around the pure exponent. The shapes of the abundance gradients and surface brightness profiles within the optical radius in a galaxy may be different. A pure exponential surface brightness profile may be accompanied by a broken abundance gradient and vise versa. There is no correlation between the break radii of the abundance gradients and surface brightness profiles. Thus, a break in the surface brightness profile does not need to be accompanied by a break in the abundance gradient.
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- ID:
- ivo://CDS.VizieR/J/A+A/633/A54
- Title:
- B0355+508 reduced spectra
- Short Name:
- J/A+A/633/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Phosphorus-bearing species are essential to the formation of life on Earth, however they have barely been detected in the interstellar medium. In particular, towards star-forming regions only PN and PO have been identified so far. Since only a small number of detections of P-bearing molecules are available, their chemical formation pathways are not easy to constrain and are thus highly debatable. An important factor still missing in the chemical models is the initial elemental abundance of phosphorus, that is, the depletion level of P at the start of chemical models of dense clouds. In order to overcome this problem, we study P-bearing species in diffuse and translucent clouds. In these objects phosphorus is expected to be mainly in the gas phase and therefore the elemental initial abundance needed in our chemical simulations corresponds to the cosmic one and is well constrained. For the study of P-bearing chemistry we used an advanced chemical model. We updated and significantly extended the P-chemistry network based on chemical databases and previous literature. We performed single-pointing observations with the IRAM 30m telescope in the 3mm range towards the line of sight to the strong continuum source B0355+508 aiming for the (2-1) transitions of PN, PO, HCP, and CP. This line of sight incorporates five diffuse and/or translucent clouds. The (2-1) transitions of the PN, PO, HCP, and CP were not detected. We report high signal-to-noise-ratio detections of the (1-0) lines of ^13^CO, HNC, and CN along with a first detection of C^34^S towards this line of sight. We have attempted to reproduce the observations of HNC, CN, CS, and CO in every cloud with our model by applying typical physical conditions for diffuse or translucent clouds. We find that towards the densest clouds with v_LSR_= -10, -17 km/s the best-fit model is given by the parameters (n_H_, A_V_, T_gas_) = (300cm^-3^, 3mag, 40K). According to our best-fit model, the most abundant P-bearing species are HCP and CP (1e-10). The molecules PN, PO, and PH_3_ also show relatively high predicted abundances of 1e-11. We show that the abundances of these species are sensitive to visual extinction, cosmic-ray ionization rate, and the diffusion-to-desorption energy ratio on dust grains. The production of P-bearing species is favored towards translucent rather than diffuse clouds, where the environment provides a stronger shielding from the interstellar radiation. Based on our improved model, we show that the (1-0) transitions of HCP, CP, PN, and PO are expected to be detectable with estimated intensities of up to ~200mK.
- ID:
- ivo://CDS.VizieR/J/ApJS/149/365
- Title:
- Bright filamentary structures in the ISM
- Short Name:
- J/ApJS/149/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a listing of prominent filamentary structures in the interstellar cirrus, selected with an eye toward current and planned far-infrared and submillimeter polarimetry facilities. The filaments were identified on the 100{mu}m plates of the IRAS Sky Survey Atlas (ISSA, Wheelock et al. 1994, IRAS Sky Survey Atlas: Explanatory Supplement (JPL Publ. 94-11; Pasadena: JPL)), using a computer vision algorithm that is unbiased with respect to source intensity. Our catalog is two-tiered: the selection criteria in the Galactic plane are based on the sensitivity limits of airborne polarimeters such as the proposed HALE instrument for SOFIA, and away from the plane the limits are dictated by the sensitivities of balloon-borne cosmic microwave background experiments, such as BOOMERanG and MAXIMA. Infrared detector technology is currently at the point where detecting the polarization of the interstellar cirrus is feasible, and we hope this catalog will assist any experimenter undertaking this task.
- ID:
- ivo://CDS.VizieR/J/ApJS/99/551
- Title:
- BVI photometry of massive stars in M33 and M31
- Short Name:
- J/ApJS/99/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BVI photometry of the massive stars in and around five Halpha shells in M33 and two in M31. These data can be used to statistically compare the stellar population with ionization and formation requirements of the gas shell. We have counted the numbers of massive stars encircled by the shells and embedded within the gaseous structures and corrected these numbers statistically for background and foreground interlopers. We find that the stellar production exceeds the ionization requirements of the nebulae by factors of 4-10. Thus, it is reasonable that the shells are photoionized and that a large fraction of the ionizing photons escape into the rest of the galaxy. We have also compared the number of massive stars counted and extrapolated to 7M_{sun}_ with the number required to form the shells according to a simple formation model. With one exception, we find that the number of stars estimated to be present exceeds the number required by the model for our assumptions of age and ambient gas density. This comparison and the morphology evident in Halpha images suggests that the modification of the interstellar medium by the massive stars in these regions has been far more complicated than is currently considered in formation models. There is evidence for multiple, and to some extent discreet, events in the production of the gas structures. A more detailed modeling will be necessary to adequately account for the stellar populations and Halpha morphology.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/38
- Title:
- Carbon and oxygen isotopic ratios for nearby Miras
- Short Name:
- J/ApJ/825/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon and oxygen isotopic ratios are reported for a sample of 46 Mira and SRa-type variable asymptotic giant branch (AGB) stars. Vibration-rotation first and second-overtone CO lines in 1.5-2.5{mu}m spectra were measured to derive isotopic ratios for ^12^C/^13^C, ^16^O/^17^O, and ^16^O/^18^O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of M-stars have main sequence masses <=2M_{sun}_ and have not experienced sizable third dredge-up (TDU) episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the six C-stars in the sample three have clear evidence relating their origin to the occurrence of TDU. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars, as represented by our sample of long period variables (LPVs), shows a large spread of ^16^O/^17^O ratios, similar to that of group 1 presolar grains and in agreement with theoretical expectations for the composition of mass 1.2-2M_{sun}_ stars after the first dredge-up. In contrast, the ^16^O/^18^O ratios of present-day LPVs are definitely smaller than those of group 1 grains. This is most probably a consequence of the the decrease with time of the ^16^O/^18^O ratio in the interstellar medium due to the chemical evolution of the Milky Way. One star in our sample has an O composition similar to that of group 2 presolar grains originating in an AGB star undergoing extra-mixing. This may indicate that the extra-mixing process is hampered at high metallicity, or, equivalently, favored at low metallicity. Similarly to O-rich grains, no star in our sample shows evidence of hot bottom burning, which is expected for massive AGB stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/61
- Title:
- Carbon and Oxygen local interstellar spectra
- Short Name:
- J/ApJ/858/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Local interstellar spectra (LIS) of primary cosmic ray (CR) nuclei, such as helium, oxygen, and mostly primary carbon are derived for the rigidity range from 10MV to ~200TV using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HelMod, are combined into a single framework that is used to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. The developed iterative maximum-likelihood method uses GALPROP- predicted LIS as input to HelMod, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The interstellar and heliospheric propagation parameters derived in this study are consistent with our prior analyses using the same methodology for propagation of CR protons, helium, antiprotons, and electrons. The resulting LIS accommodate a variety of measurements made in the local interstellar space (Voyager 1) and deep inside the heliosphere at low (ACE/CRIS, HEAO-3) and high energies (PAMELA, AMS-02).
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2442
- Title:
- Catalog of bubbles from Milky Way Project
- Short Name:
- J/MNRAS/424/2442
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalogue of 5106 infrared bubbles created through visual classification via the online citizen science website The Milky Way Project. Bubbles in the new catalogue have been independently measured b at least five individuals, producing consensus parameters for their position, radius, thickness, eccentricity and position angle. Citizen scientists - volunteers recruited online and taking part in this research - have independently rediscovered the locations of at least 86 percent of three widely used catalogues of bubbles and HII regions whilst finding an order of magnitude more objects. 29 per cent of the Milky Way Project catalogue bubbles lie on the rim of a larger bubble, or have smaller bubbles located within them, opening up the possibility of better statistical studies of triggered star formation. Also outlined is the creation of a heat map of star formation activity in the Galactic plane. This online resource provides a crowd-sourced map of bubbles and arcs in the Milky Way, and will enable better statistical analysis of Galactic star formation sites.
- ID:
- ivo://CDS.VizieR/J/A+A/584/A91
- Title:
- Catalog of dense cores in Aquila from Herschel
- Short Name:
- J/A+A/584/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and discuss the results of the Herschel Gould Belt survey (HGBS) observations in an ~11deg^2^ area of the Aquila molecular cloud complex at d~260pc, imaged with the SPIRE and PACS photometric cameras in parallel mode from 70-micron to 500-micron. Using the multi-scale, multi-wavelength source extraction algorithm getsources, we identify a complete sample of starless dense cores and embedded (Class 0-I) protostars in this region, and analyze their global properties and spatial distributions. We find a total of 651 starless cores, ~60% +/-10% of which are gravitationally bound prestellar cores, and they will likely form stars in the future. We also detect 58 protostellar cores. The core mass function (CMF) derived for the large population of prestellar cores is very similar in shape to the stellar initial mass function (IMF), confirming earlier findings on a much stronger statistical basis and supporting the view that there is a close physical link between the stellar IMF and the prestellar CMF. The global shift in mass scale observed between the CMF and the IMF is consistent with a typical star formation efficiency of ~40% at the level of an individual core. By comparing the numbers of starless cores in various density bins to the number of young stellar objects (YSOs), we estimate that the lifetime of prestellar cores is ~1Myr, which is typically ~4 times longer than the core free-fall time, and that it decreases with average core density. We find a strong correlation between the spatial distribution of prestellar cores and the densest filaments observed in the Aquila complex. About 90% of the Herschel-identified prestellar cores are located above a background column density corresponding to A_V_~7, and ~75% of them lie within filamentary structures with supercritical masses per unit length >~16M_{sun}_/pc. These findings support a picture wherein the cores making up the peak of the CMF (and probably responsible for the base of the IMF) result primarily from the gravitational fragmentation of marginally supercritical filaments. Given that filaments appear to dominate the mass budget of dense gas at A_V_>7, our findings also suggest that the physics of prestellar core formation within filaments is responsible for a characteristic "efficiency" SFR/M_dense_~5+/-2x10^-8^yr^-1^ for the star formation process in dense gas.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A74
- Title:
- Catalog of dense cores in Oph molecular cloud
- Short Name:
- J/A+A/638/A74
- Date:
- 02 Mar 2022 11:56:27
- Publisher:
- CDS
- Description:
- Herschel observations of nearby clouds in the Gould Belt support a paradigm for low-mass star formation, starting with the generation of molecular filaments, followed by filament fragmentation, and the concentration of mass into self-gravitating prestellar cores. With the unique far-infrared and submillimeter continuum imaging capabilities of the Herschel Space observatory, the closeby (d=139pc) Ophiuchus cloud was mapped at five wavelengths from 70 microns to 500 microns with the aim of providing a complete census of dense cores in this region, including unbound starless cores, bound prestellar cores, and protostellar cores. Taking advantage of the high dynamic range and multi-wavelength nature of the Herschel data, we used the multi-scale decomposition algorithms getsources and getfilaments to identify a complete sample of dense cores and filaments in the cloud and study their properties. The densest clouds of the Ophiuchus complex, L1688 and L1689, which thus far are only indirectly described as filamentary regions owing to the spatial distribution of their young stellar objects (YSOs), are confirmed to be dominated by filamentary structures. The tight correlation observed between prestellar cores and filamentary structures in L1688 and L1689 supports the view that solar-type star formation occurs primarily in dense filaments. While the sub clouds of the complex show disparities, L1689 being less efficient than L1688 at forming stars when considering their total mass budgets, both sub clouds share almost the same prestellar core formation efficiency in dense molecular gas. We also find evidence in the Herschel data for a remarkable concentric geometrical configuration in L1688 which is dominated by up to three arc-like compression fronts and presumably created by shockwave events emanating from the Sco OB2 association, including the neighboring massive (O9V) star sigma Sco.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A34
- Title:
- Catalog of dense cores in Orion B from Herschel
- Short Name:
- J/A+A/635/A34
- Date:
- 14 Jan 2022 08:07:23
- Publisher:
- CDS
- Description:
- We present a detailed study of the Orion B molecular cloud complex (d~400pc), which was imaged with the PACS and SPIRE photometric cameras at wavelengths from 70-micron to 500-micron as part of the Herschel Gould Belt survey (HGBS). We release new high-resolution maps of column density and dust temperature for the whole complex, derived in the same consistent manner as for other HGBS regions. In the filamentary subregions NGC2023 and 2024, NGC2068 and 2071, and L1622, a total of 1768 starless dense cores were identified based on Herschel data, 490-804 (~28-45%) of which are self-gravitating prestellar cores that will likely form stars in the future. A total of 76 protostellar dense cores were also found. The typical lifetime of the prestellar cores was estimated to be t_pre_^OrionB^=1.7(-0.6/+0.8)Myr. The prestellar core mass function (CMF) derived for the whole sample of prestellar cores peaks at ~0.5Msun (in dN/dlogM format) and is consistent with a power-law with logarithmic slope -1.27+/-0.24 at the high-mass end, compared to the Salpeter slope of -1.35. In the Orion B region, we confirm the existence of a transition in prestellar core formation efficiency (CFE) around a fiducial value A_V_^bg^~7mag in background visual extinction, which is similar to the trend observed with Herschel in other regions, such as the Aquila cloud. This is not a sharp threshold, however, but a smooth transition between a regime with very low prestellar CFE at A_V_^bg^<5 and a regime with higher, roughly constant CFE at A_V_^bg^>~10. The total mass in the form of prestellar cores represents only a modest fraction (~20%) of the dense molecular cloud gas above A_V_^bg^>~7mag. About 60-80% of the prestellar cores are closely associated with filaments, and this fraction increases up to >90% when a more complete sample of filamentary structures is considered. Interestingly, the median separation observed between nearest core neighbors corresponds to the typical inner filament width of ~0.1pc, which is commonly observed in nearby molecular clouds, including Orion B. Analysis of the CMF observed as a function of background cloud column density shows that the most massive prestellar cores are spatially segregated in the highest column density areas, and suggests that both higher- and lower-mass prestellar cores may form in denser filaments.
