60 research outputs found
Human Consumption of Microplastics
Microplastics are ubiquitous across ecosystems, yet the exposure risk to humans is unresolved. Focusing on the American diet, we evaluated the number of microplastic particles in commonly consumed foods in relation to their recommended daily intake. The potential for microplastic inhalation and how the source of drinking water may affect microplastic consumption were also explored. Our analysis used 402 data points from 26 studies, which represents over 3600 processed samples. Evaluating approximately 15% of Americans’ caloric intake, we estimate that annual microplastics consumption ranges from 39000 to 52000 particles depending on age and sex. These estimates increase to 74000 and 121000 when inhalation is considered. Additionally, individuals who meet their recommended water intake through only bottled sources may be ingesting an additional 90000 microplastics annually, compared to 4000 microplastics for those who consume only tap water. These estimates are subject to large amounts of variation; however, given methodological and data limitations, these values are likely underestimates
Spectroscopic FIR mapping of the disk and galactic wind of M82 with Herschel-PACS
[Abridged] We present maps of the main cooling lines of the neutral atomic
gas ([OI] at 63 and 145 micron and [CII] at 158 micron) and in the [OIII] 88
micron line of the starburst galaxy M82, carried out with the PACS spectrometer
on board the Herschel satellite. By applying PDR modeling we derive maps of the
main ISM physical parameters, including the [CII] optical depth, at
unprecedented spatial resolution (~300 pc). We can clearly kinematically
separate the disk from the outflow in all lines. The [CII] and [OI]
distributions are consistent with PDR emission both in the disk and in the
outflow. Surprisingly, in the outflow, the atomic and the ionized gas traced by
the [OIII] line both have a deprojected velocity of ~75 km/s, very similar to
the average velocity of the outflowing cold molecular gas (~ 100 km/s) and
several times smaller than the outflowing material detected in Halpha (~ 600
km/s). This suggests that the cold molecular and neutral atomic gas and the
ionized gas traced by the [OIII] 88 micron line are dynamically coupled to each
other but decoupled from the Halpha emitting gas. We propose a scenario where
cold clouds from the disk are entrained into the outflow by the winds where
they likely evaporate, surviving as small, fairly dense cloudlets (n_H\sim
500-1000 cm^-3, G_0\sim 500- 1000, T_gas\sim300 K). We show that the UV photons
provided by the starburst are sufficient to excite the PDR shells around the
molecular cores. The mass of the neutral atomic gas in the outflow is \gtrsim
5-12x 10^7 M_sun to be compared with that of the molecular gas (3.3 x 10^8
M_sun) and of the Halpha emitting gas (5.8 x 10^6 M_sun). The mass loading
factor, (dM/dt)/SFR, of the molecular plus neutral atomic gas in the outflow is
~ 2. Energy and momentum driven outflow models can explain the data equally
well, if all the outflowing gas components are taken into account.Comment: 26 pages, 23 figures, 4 Tables, Accepted for publication in Astronomy
& Astrophysic
Herschel-PACS Observations of Far-IR CO Line Emission in NGC 1068: Highly Excited Molecular Gas in the Circumnuclear Disk
We report the detection of far-IR CO rotational emission from the
prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected
11 transitions in the J_upper=14-30 (E_upper/k_B = 580-2565 K) range, all of
which are consistent with arising from within the central 10" (700 pc). The
detected transitions are modeled as arising from 2 different components: a
moderate excitation (ME) component close to the galaxy systemic velocity, and a
high excitation (HE) component that is blueshifted by ~80 km s^{-1}. We employ
a large velocity gradient (LVG) model and derive n_H2~10^{5.6} cm^{-3},
T_kin~170 K, and M_H2~10^{6.7} M_sun for the ME component, and n_H2~10^{6.4}
cm^{-3}, T_kin~570 K, and M_H2~10^{5.6} M_sun for the HE component, although
for both components the uncertainties in the density and mass are plus/minus
(0.6-0.9) dex. We compare the CO line profiles with those of other molecular
tracers observed at higher spatial and spectral resolution, and find that the
ME transitions are consistent with these lines arising in the ~200 pc diameter
ring of material traced by H_2 1-0 S(1) observations. The blueshift of the HE
lines may also be consistent with the bluest regions of this H_2 ring, but a
better kinematic match is found with a clump of infalling gas ~40 pc north of
the AGN. We discuss the prospects of placing the HE component near the AGN, and
conclude that while the moderate thermal pressure precludes an association with
the ~1 pc radius H_2O maser disk, the HE component could potentially be located
only a few parsecs more distant from the AGN, and might then provide the
N_H~10^{25} cm^{-2} column obscuring the nuclear hard X-rays. Finally, we also
report sensitive upper limits extending up to J_upper=50, which place
constraints on a previous model prediction for the CO emission from the X-ray
obscuring torus. [Abridged]Comment: 20 pages, 10 figures. Accepted for publication in Ap
A deep Herschel/PACS observation of CO(40-39) in NGC 1068: a search for the molecular torus
Emission from high-J CO lines in galaxies has long been proposed as a tracer
of X-ray dominated regions (XDRs) produced by AGN. Of particular interest is
the question of whether the obscuring torus, which is required by AGN
unification models, can be observed via high-J CO cooling lines. Here we report
on the analysis of a deep Herschel-PACS observation of an extremely high J CO
transition (40-39) in the Seyfert 2 galaxy NGC 1068. The line was not detected,
with a derived 3 upper limit of . We apply an XDR model in order to
investigate whether the upper limit constrains the properties of a molecular
torus in NGC 1068. The XDR model predicts the CO Spectral Line Energy
Distributions for various gas densities and illuminating X-ray fluxes. In our
model, the CO(40-39) upper limit is matched by gas with densities , located at from the AGN,
with column densities of at least . At such high
column densities, however, dust absorbs most of the CO(40-39) line emission at
m. Therefore, even if NGC 1068 has a molecular torus
which radiates in the CO(40-39) line, the dust can attenuate the line emission
to below the PACS detection limit. The upper limit is thus consistent with the
existence of a molecular torus in NGC 1068. In general, we expect that the
CO(40-39) is observable in only a few AGN nuclei (if at all), because of the
required high gas column density, and absorption by dust.Comment: 22 pages, accepted for publication in Ap
Excited OH+, H2O+, and H3O+ in NGC 4418 and Arp 220
We report on Herschel/PACS observations of absorption lines of OH+, H2O+ and
H3O+ in NGC 4418 and Arp 220. Excited lines of OH+ and H2O+ with E_lower of at
least 285 and \sim200 K, respectively, are detected in both sources, indicating
radiative pumping and location in the high radiation density environment of the
nuclear regions. Abundance ratios OH+/H2O+ of 1-2.5 are estimated in the nuclei
of both sources. The inferred OH+ column and abundance relative to H nuclei are
(0.5-1)x10^{16} cm-2 and \sim2x10^{-8}, respectively. Additionally, in Arp 220,
an extended low excitation component around the nuclear region is found to have
OH+/H2O+\sim5-10. H3O+ is detected in both sources with
N(H3O+)\sim(0.5-2)x10^{16} cm-2, and in Arp 220 the pure inversion, metastable
lines indicate a high rotational temperature of ~500 K, indicative of formation
pumping and/or hot gas. Simple chemical models favor an ionization sequence
dominated by H+ - O+ - OH+ - H2O+ - H3O+, and we also argue that the H+
production is most likely dominated by X-ray/cosmic ray ionization. The full
set of observations and models leads us to propose that the molecular ions
arise in a relatively low density (\gtrsim10^4 cm-3) interclump medium, in
which case the ionization rate per H nucleus (including secondary ionizations)
is zeta>10^{-13} s-1, a lower limit that is severalx10^2 times the highest rate
estimates for Galactic regions. In Arp 220, our lower limit for zeta is
compatible with estimates for the cosmic ray energy density inferred previously
from the supernova rate and synchrotron radio emission, and also with the
expected ionization rate produced by X-rays. In NGC 4418, we argue that X-ray
ionization due to an AGN is responsible for the molecular ion production.Comment: 24 pages, 13 figures. Accepted for publication in Astronomy &
Astrophysic
High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS
We report the detection of far-infrared (FIR) CO rotational emission from
nearby active galactic nuclei (AGN) and starburst galaxies, as well as several
merging systems and Ultra-Luminous Infrared Galaxies (ULIRGs). Using
Herschel-PACS, we have detected transitions in the J = 14 - 20 range
( 130 - 185 m, 1612 - 2300 GHz) with upper limits
on (and in two cases, detections of) CO line fluxes up to J = 30. The
PACS CO data obtained here provide the first well-sampled FIR extragalactic CO
SLEDs for this range, and will be an essential reference for future high
redshift studies. We find a large range in the overall SLED shape, even amongst
galaxies of similar type, demonstrating the uncertainties in relying solely on
high-J CO diagnostics to characterize the excitation source of a galaxy.
Combining our data with low-J line intensities taken from the literature, we
present a CO ratio-ratio diagram and discuss its potential diagnostic value in
distinguishing excitation sources and physical properties of the molecular gas.
The position of a galaxy on such a diagram is less a signature of its
excitation mechanism, than an indicator of the presence (or absence) of warm,
dense molecular gas. We then quantitatively analyze the CO emission from a
subset of the detected sources with Large Velocity Gradient (LVG) radiative
transfer models to fit the CO SLEDs. Using both single-component and
two-component LVG models to fit the kinetic temperature, velocity gradient,
number density and column density of the gas, we derive the molecular gas mass
and the corresponding CO-to-H conversion factor, , for each
respective source. For the ULIRGs we find values in the canonical
range 0.4 - 5 M/(K kmspc), while for the other objects,
varies between 0.2 and 14.} Finally, we compare our best-fit LVG model
..Comment: 39 pages, 3 figures; Accepted to Ap
ISM conditions in z~0.2 Lyman-Break Analogs
We present an analysis of far--infrared (FIR) [CII] and [OI] fine structure
line and continuum observations obtained with /PACS, and CO(1-0)
observations obtained with the IRAM Plateau de Bure Interferometer, of Lyman
Break Analogs (LBAs) at . The principal aim of this work is to
determine the typical ISM properties of Main Sequence (MS)
galaxies, with stellar masses between and ,
which are currently not easily detectable in all these lines even with ALMA and
NOEMA. We perform PDR modeling and apply different IR diagnostics to derive the
main physical parameters of the FIR emitting gas and dust and we compare the
derived ISM properties to those of galaxies on and above the MS at different
redshifts. We find that the ISM properties of LBAs are quite extreme (low gas
temperature, high density and thermal pressure) with respect to those found in
local normal spirals and more active local galaxies. LBAs have no [CII] deficit
despite having the high specific star formation rates (sSFRs) typical of
starbursts. Although LBAs lie above the local MS, we show that their ISM
properties are more similar to those of high-redshift MS galaxies than of local
galaxies above the main sequence. This data set represents an important
reference for planning future ALMA [CII] observations of relatively low-mass MS
galaxies at the epoch of the peak of the cosmic star formation.Comment: 19 pages, 12 Figures,8 Tables, Accepted for publication in A&
Herschel PACS Spectroscopic Diagnostics of Local ULIRGs: Conditions and Kinematics in Mrk 231
In this first paper on the results of our Herschel PACS survey of local
Ultraluminous Infrared Galaxies (ULIRGs), as part of our SHINING survey of
local galaxies, we present far-infrared spectroscopy of Mrk 231, the most
luminous of the local ULIRGs, and a type 1 broad absorption line AGN. For the
first time in a ULIRG, all observed far-infrared fine-structure lines in the
PACS range were detected and all were found to be deficient relative to the far
infrared luminosity by 1 - 2 orders of magnitude compared with lower luminosity
galaxies. The deficits are similar to those for the mid-infrared lines, with
the most deficient lines showing high ionization potentials. Aged starbursts
may account for part of the deficits, but partial covering of the highest
excitation AGN powered regions may explain the remaining line deficits. A
massive molecular outflow, discovered in OH and 18OH, showing outflow
velocities out to at least 1400 km/sec, is a unique signature of the clearing
out of the molecular disk that formed by dissipative collapse during the
merger. The outflow is characterized by extremely high ratios of 18O / 16O
suggestive of interstellar medium processing by advanced starbursts.Comment: Accepted for publication in the Astronomy and Astrophysics Herschel
Special Issue, 5 pages, 4 figure
Far-Infrared Line Deficits in Galaxies with Extreme Lfir/MH2 Ratios
We report initial results from the far-infrared fine structure line
observations of a sample of 44 local starbursts, Seyfert galaxies and infrared
luminous galaxies obtained with the PACS spectrometer on board Herschel. We
show that the ratio between the far-infrared luminosity and the molecular gas
mass, Lfir/MH2, is a much better proxy for the relative brightness of the
far-infrared lines than Lfir alone. Galaxies with high Lfir/MH2 ratios tend to
have weaker fine structure lines relative to their far-infrared continuum than
galaxies with Lfir/MH2 < 80 Lsun/Msun. A deficit of the [C II] 158 micron line
relative to Lfir was previously found with the ISO satellite, but now we show
for the first time that this is a general aspect of all far-infrared fine
structure lines, regardless of their origin in the ionized or neutral phase of
the interstellar medium. The Lfir/MH2 value where these line deficits start to
manifest is similar to the limit that separates between the two modes of star
formation recently found in galaxies on the basis of studies of their gas-star
formation relations. Our finding that the properties of the interstellar medium
are also significantly different in these regimes provides independent support
for the different star forming relations in normal disk galaxies and major
merger systems. We use the spectral synthesis code Cloudy to model the emission
of the lines. The expected increase of the ionization parameter with Lfir/MH2
can simultaneously explain the line deficits in the [C II], [N II] and [O I]
lines.Comment: Accepted for publication in ApJ Letters; 5 pages, 3 figure
Excited OH^+, H_2O^+, and H_3O^+ in NGC 4418 and Arp 220
We report on Herschel/PACS observations of absorption lines of OH^+, H_2O^+ and H_3O^+ in NGC 4418 and Arp 220. Excited lines of OH^+ and H_2O^+ with E_(lower) of at least 285 and ~200 K, respectively, are detected in both sources, indicating radiative pumping and location in the high radiation density environment of the nuclear regions. Abundance ratios OH^+/H_2O^+ of 1−2.5 are estimated in the nuclei of both sources. The inferred OH^+ column and abundance relative to H nuclei are (0.5−1) × 10^(16) cm^(-2) and ~ 2 × 10^(-8), respectively. Additionally, in Arp 220, an extended low excitation component around the nuclear region is found to have OH^+/H^2O^+ ~ 5−10. H_3O^+ is detected in both sources with N(H_3O^+) ~ (0.5−2) × 10^(16) cm^(-2), and in Arp 220 the pure inversion, metastable lines indicate a high rotational temperature of ~500 K, indicative of formation pumping and/or hot gas. Simple chemical models favor an ionization sequence dominated by H^+ → O^+ → OH^+ → H_2O^+ → H_3O^+, and we also argue that the H^+ production is most likely dominated by X-ray/cosmic ray ionization. The full set of observations and models leads us to propose that the molecular ions arise in a relatively low density (≳10^4 cm^(-3)) interclump medium, in which case the ionization rate per H nucleus (including secondary ionizations) is ζ > 10^(-13) s^(-1), a lower limit that is several × 10^2 times the highest current rate estimates for Galactic regions. In Arp 220, our lower limit for ζ is compatible with estimates for the cosmic ray energy density inferred previously from the supernova rate and synchrotron radio emission, and also with the expected ionization rate produced by X-rays. In NGC 4418, we argue that X-ray ionization due to an active galactic nucleus is responsible for the molecular ion production
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