Aims. The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the ...DustPedia sample. Methods. This study is performed by exploiting the multi-wavelength DustPedia database, from ultraviolet (UV) to sub-millimeter bands, in addition to molecular (12CO) and atomic (Hi) gas maps and metallicity abundance information available in the literature. We fitted the surface-brightness profiles of the tracers of dust and stars, the mass surface-density profiles of dust, stars, molecular gas, and total gas, and the SFR surface-density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (αCO) per galaxy by using dust- and gas-mass profiles. Results. Although each galaxy has its own peculiar behavior, we identified a common trend of the exponential scale-lengths versus wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec2 radius decrease from UV to 70 μm, from 0.4 to 0.2, and then increase back up to ~0.3 at 500 microns. The main result is that, on average, the dust-mass surface-density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 μm surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 μm scale-length tend to increase from earlier to later types, the scale-length at 70 μm tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 μm that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types. Our αCO determinations are in the range (0.3−9) M⊙ pc-2 (K km s-1)-1, almost invariant by using a fixed dust-to-gas ratio mass (DGR) or a DGR depending on metallicity gradient.
Aims.
The purpose of this work is the characterization of the main scaling relations between all of the interstellar medium (ISM) components, namely dust, atomic, molecular, and total gas, and ...gas-phase metallicity, as well as other galaxy properties, such as stellar mass (
M
star
) and galaxy morphology, for late-type galaxies in the Local Universe.
Methods.
This study was performed by extracting late-type galaxies from the entire DustPedia sample and by exploiting the large and homogeneous dataset available thanks to the DustPedia project. The sample consists of 436 galaxies with morphological stage spanning from
T
= 1−10,
M
star
from 6 × 10
7
to 3 × 10
11
M
⊙
, star formation rate from 6 × 10
−4
to 60
M
⊙
yr
−1
, and oxygen abundance from 12 + log(O/H) = 8−9.5. Molecular and atomic gas data were collected from the literature and properly homogenized. All the masses involved in our analysis refer to the values within the optical disks of galaxies. The scaling relations involving the molecular gas are studied by assuming both a constant and a metallicity-dependent CO-to-H
2
conversion factor (
X
CO
). The analysis was performed by means of the survival analysis technique, in order to properly take into account the presence of both detection and nondetection in the data.
Results.
We confirm that the dust mass correlates very well with the total gas mass, and find –for the first time– that the dust mass correlates better with the atomic gas mass than with the molecular one. We characterize important mass ratios such as the gas fraction, the molecular-to-atomic gas mass ratio, the dust-to-total gas mass ratio (DGR), and the dust-to-stellar mass ratio, and study how they relate to each other, to galaxy morphology, and to gas-phase metallicity. Only the assumption of a metallicity-dependent
X
CO
reproduces the expected decrease of the DGR with increasing morphological stage and decreasing gas-phase metallicity, with a slope of about 1. The DGR, the gas-phase metallicity, and the dust-to-stellar mass ratio are, for our galaxy sample, directly linked to galaxy morphology. The molecular-to-atomic gas mass ratio and the DGR show a positive correlation for low molecular gas fractions, but for galaxies rich in molecular gas this trend breaks down. To our knowledge, this trend has never been found before, and provides new constraints for theoretical models of galaxy evolution and a reference for high-redshift studies. We discuss several scenarios related to this finding.
Conclusions.
The DustPedia database of late-type galaxies is an extraordinary tool for the study of the ISM scaling relations, thanks to its homogeneous collection of data for the different ISM components. The database is made publicly available to the whole community.
ABSTRACT
We report evidence for star formation quenching in the central 8.6 kpc region of the jellyfish galaxy JO201 that hosts an active galactic nucleus (AGN), while undergoing strong ram-pressure ...stripping. The ultraviolet imaging data of the galaxy disc reveal a region with reduced flux around the centre of the galaxy and a horse-shoe-shaped region with enhanced flux in the outer disc. The characterization of the ionization regions based on emission line diagnostic diagrams shows that the region of reduced flux seen in the ultraviolet is within the AGN-dominated area. The CO J2−1 map of the galaxy disc reveals a cavity in the central region. The image of the galaxy disc at redder wavelengths (9050–9250 Å) reveals the presence of a stellar bar. The star formation rate map of the galaxy disc shows that the star formation suppression in the cavity occurred in the last few 108 yr. We present several lines of evidence supporting the scenario that suppression of star formation in the central region of the disc is most likely due to the feedback from the AGN. The observations reported here make JO201 a unique case of AGN feedback and environmental effects suppressing star formation in a spiral galaxy.
Following deglaciation, the long-term pattern of change in diatom communities and the inferred history of the aquatic environment are affected by a hierarchy of environmental controls. These include ...direct climate impacts on a lake’s thermal and hydrologic budgets, as well as the indirect affects of climate on catchment processes, such as weathering, soil development, microbial activity, fire, and vegetation composition and productivity, which affect the transfer of solutes and particulates from the terrestrial ecosystem into the lake. Some of these catchment influences on lacustrine systems operate as time-dependent patterns of primary succession that are set in motion by glacier retreat. This paper provides a conceptual model of some dominant pathways of catchment influence on long-term lake development in glaciated regions and uses a series of paleolimnological examples from arctic, boreal, and temperate regions to evaluate the relative role of direct climate influences and of catchment processes in affecting the trajectory of aquatic ecosystems during the Holocene in different environmental contexts.
We present a new measurement of the systemic proper motion of the Small Magellanic Cloud (SMC), based on an expanded set of 30 fields containing background quasars and spanning a ∼3 year baseline, ...using the Hubble Space Telescope (HST) Wide Field Camera 3. Combining this data with our previous five HST fields, and an additional eight measurements from the Gaia-Tycho Astrometric Solution Catalog, brings us to a total of 43 SMC fields. We measure a systemic motion of W = −0.82 0.02 (random) 0.10 (systematic) mas yr−1 and N = −1.21 0.01 (random) 0.03 (systematic) mas yr−1. After subtraction of the systemic motion, we find little evidence for rotation, but find an ordered mean motion radially away from the SMC in the outer regions of the galaxy, indicating that the SMC is in the process of tidal disruption. We model the past interactions of the Clouds with each other based on the measured present-day relative velocity between them of 103 26 km s−1. We find that in 97% of our considered cases, the Clouds experienced a direct collision 147 33 Myr ago, with a mean impact parameter of 7.5 2.5 kpc.
The role of the Arctic in future global change processes is predicted to be important because of the large carbon (C) stocks contained in frozen soils and peatlands. Lakes are an important component ...of arctic landscapes although their role in storing C is not well prescribed. The area around Kangerlussuaq, SW Greenland (66-68°N, 49-54°W) has extremely high lake density, with ~20 000 lakes that cover about 14% of the land area. C accumulation rates and standing stock (kg C m⁻²), representing late- to mid-Holocene C burial, were calculated from AMS ¹⁴C-dated sediment cores from 11 lakes. Lake ages range from ~10 000 cal yr bp to ~5400 cal yr bp, and reflect the withdrawal of the ice sheet from west to east. Total standing stock of C accumulated in the studied lakes for the last ~8000 years ranged from 28 to 71 kg C m⁻², (mean: ~42 kg C m⁻²). These standing stock determinations yield organic C accumulation rates of 3.5-11.5 g C m⁻² yr⁻¹ (mean: ~6 g C m⁻² yr⁻¹) for the last 4500 years. Mean C accumulation rates are not different for the periods 8-4.5 and 4.5-0 ka, despite cooling trends associated with the neoglacial period after 4.5 ka. We used the mean C standing stock to estimate the total C pool in small lakes (<100 ha) of the Kangerlussuaq region to be ~4.9 x 10¹³ g C. This C stock is about half of that estimated for the soil pool in this region (but in 5% of the land area) and indicates the importance of incorporating lakes into models of regional C balance at high latitudes.
Aims. Within the framework of the DustPedia project we investigate the properties of cosmic dust and its interaction with stellar radiation (originating from different stellar populations) for 814 ...galaxies in the nearby Universe, all observed by the Herschel Space Observatory. Methods. We take advantage of the widely used fitting code CIGALE, properly adapted to include the state-of-the-art dust model THEMIS. For comparison purposes, an estimation of the dust properties is provided by approximating the emission at far-infrared and sub-millimeter wavelengths with a modified blackbody. Using the DustPedia photometry we determine the physical properties of the galaxies, such as the dust and stellar mass, the star-formation rate, the bolometric luminosity, the unattenuated and the absorbed by dust stellar light, for both the old (> 200 Myr) and young (≤200 Myr) stellar populations. Results. We show how the mass of stars, dust, and atomic gas, as well as the star-formation rate and the dust temperature vary between galaxies of different morphologies and provide recipes to estimate these parameters given their Hubble stage (T). We find a mild correlation between the mass fraction of the small a-C(:H) grains with the specific star-formation rate. On average, young stars are very efficient in heating the dust, with absorption fractions reaching as high as ∼77% of the total unattenuated luminosity of this population. On the other hand, the maximum absorption fraction of old stars is ∼24%. Dust heating in early-type galaxies is mainly due to old stars, up to a level of ∼90%. Young stars progressively contribute more for “typical” spiral galaxies and they become the dominant source of dust heating for Sm-type and irregular galaxies, with ∼60% of their luminosity contributing to that purpose. Finally, we find a strong correlation of the dust heating fraction by young stars with morphology and the specific star-formation rate.
Lakes are a key feature of arctic landscapes and can be an important component of regional organic carbon (OC) budgets, but C burial rates are not well estimated. ²¹⁰Pb-dated sediment cores and ...carbon and organic matter (as loss-on-ignition) content were used to estimate OC burial for 16 lakes in SW Greenland. Burial rates were corrected for sediment focusing using the ²¹⁰Pb flux method. The study lakes span a range of water chemistries (conductivity range 25–3400 lS cm⁻¹), areas (< 4–100 ha) and maximum depths (~ 10–50 m). The regional average focusing-corrected OC accumulation rate was ~ 2 g C m⁻² y⁻¹ prior to 1950 and 3.6 g C m⁻² y⁻¹ after 1950. Among-lake variability in post-1950 OC AR was correlated with in-lake dissolved organic carbon concentration, conductivity, altitude and location along the fjord. Twelve lakes showed an increase in mean OC AR over the analyzed time period, ~ 1880–2000; as the study area was cooling until recently, this increase is probably attributable to other global change processes, for example, altered inputs of N or P. There are ~ 20,000 lakes in the study area ranging from ~ 1 ha to more than 130 km², although over 83% of lakes are less than 10 ha. Extrapolating the mean post-1950 OC AR (3.6 g C m⁻² y⁻¹) to all lakes larger than 1000 ha and applying a lower rate of ~ 2gCm⁻² y⁻¹ to large lakes (> 1000 ha) suggests a regional annual lake OC burial rate of ~ 10.14 × 10⁹ g C y⁻¹ post 1950. Given the low C content of soils in this area, lakes represent a substantial regional C store.
Volcanism is one of the major natural processes emitting mercury (Hg) to the atmosphere, representing a significant component of the global Hg budget. The importance of volcanic eruptions for ...local-scale Hg deposition was investigated using analyses of Hg, inorganic elemental tracers, and organic biomarkers in a sediment sequence from Lake Chungará (4520 m a.s.l.). Environmental change and Hg deposition in the immediate vicinity of the Parinacota volcano were reconstructed over the last 2700 years, encompassing the pre-anthropogenic and anthropogenic periods. Twenty eruptions delivering large amounts of Hg (1 to 457 μg Hg m−2 yr−1 deposited at the timescale of the event) were locally recorded. Peaks of Hg concentration recorded after most of the eruptions were attributed to a decrease in sedimentation rate together with the rapid re-oxidation of gaseous elemental Hg and deposition with fine particles and incorporation into lake primary producers. Over the study period, the contribution of volcanic emissions has been estimated as 32% of the total Hg input to the lake. Sharp depletions in primary production occurred at each eruption, likely resulting from massive volcaniclastic inputs and changes in the lake-water physico-chemistry. Excluding the volcanic deposition periods, Hg accumulation rates rose from natural background values (1.9 ± 0.5 μg m−2 yr−1) by a factor of 2.3 during the pre-colonial mining period (1400–900 yr cal. BP), and by a factor of 6 and 7.6, respectively, during the Hispanic colonial epoch (400–150 yr cal. BP) and the industrial era (~140 yr cal. BP to present). Altogether, the dataset indicates that lake primary production has been the main, but not limiting, carrier for Hg to the sediment. Volcanic activity and climate change are only secondary drivers of local Hg deposition relative to the magnitude of regional and global anthropogenic emissions.
Display omitted
•We studied mercury deposition in Lake Chungará (18°S) over the last ~2700 years.•Parinacota volcano produced 20 tephra layers recorded in lake sediments.•Lake primary production was the main, not limiting, carrier of Hg to the sediment.•Volcanoes contributed to ~30% of Hg inputs to the lake over the study period.•Last 400 years anthropogenic Hg emissions overwhelmed the volcanic activities.
PDF
