83 research outputs found
First interferometric study of enhanced N-fractionation in NH: the high-mass star-forming region IRAS 05358+3543
Nitrogen (N) fractionation is used as a tool to search for a link between the
chemical history of the Solar System and star-forming regions. A large
variation of N/N is observed towards different astrophysical
sources, and current chemical models cannot reproduce it. With the advent of
high angular resolution radiotelescopes it is now possible to search for
N-fractionation at core scales. We present IRAM NOEMA observations of the J=1-0
transition of NH, NNH and NNNH towards
the high-mass protocluster IRAS 05358+3543. We find N/N ratios
that span from 100 up to 220 and these values are lower or equal
than those observed with single-dish observations towards the same source.
Since N-fractionation changes across the studied region, this means that it is
regulated by local environmental effects. We find also the possibility, for one
of the four cores defined in the protocluster, to have a more abundant
NNH with respect to NNNH. This is another indication
that current chemical models may be missing chemical reactions or may not take
into account other mechanisms, like photodissociation or grain surface
chemistry, that could be important.Comment: 19 pages, 8 figures, 6 tables, 3 appendices Accepted in Monthly
Notices of the Royal Astronomical Society Letter
Identification of Histopathological Criteria for the Diagnosis of Canine Cutaneous Progressive Angiomatosis
The term angiomatosis is used to denote a group of well-known to poorly characterized
proliferative vascular entities. In animals, cutaneous progressive angiomatosis (CPA) is a disorder
with variable prognosis related to the extension and depth of infiltration of the surrounding tissues
by vessels. CPA may share some microscopical features with other vascular proliferations such as
low-grade well-differentiated capillaritic hemangiosarcoma (HS), making the diagnosis not always
straightforward, especially in small biopsies. The aim of this study is to retrospectively assess the most
common diagnostic microscopical features of CPA in dogs. In this work, 11 histopathological criteria
were analyzed on 31 CPA and 11 primary cutaneous HS in dogs. Features significantly associated with
CPA included: lobular growth, interposition of connective tissue and adnexa between the vascular
proliferation, presence of nerve fibers, and a mixed vascular proliferative component. Absence of
plump/prominent endothelial cells, lack of atypia, and lack of mitoses were also significant factors
differentiating CPA from HS. Additional distinctive findings in CPA, although with no statistical
association to CPA diagnosis, were vascular shunting, absence of necrosis, and endothelial cell piling
up. In conclusion, the combined use of different microscopical clues allowed for the distinction of
CPA from HS and was considered useful for the diagnosis of CPA
PREVALENCE OF BYOGENES AMMINS IN SEASONED D.O.P. CHEESE TOSCANO PECORINO
Pecorino cheese is one of the “D.O.P.” products made in Tuscany. There are two types of pecorino cheese one of which undergoes a curing time period which is not less than four months. Considering this curing time period, processes are conceivable that could lead to the formation of amines such as free amino acids. The biogenic amines have unquestionable effects on health in particular histamine and tyramine, they are also important indicators of hygienic quality of the profile of the movement shortly after the curing time period and included in the shelf life period which the product is commercialized
Laser Cooling of Optically Trapped Molecules
Calcium monofluoride (CaF) molecules are loaded into an optical dipole trap
(ODT) and subsequently laser cooled within the trap. Starting with
magneto-optical trapping, we sub-Doppler cool CaF and then load CaF
molecules into an ODT. Enhanced loading by a factor of five is obtained when
sub-Doppler cooling light and trapping light are on simultaneously. For trapped
molecules, we directly observe efficient sub-Doppler cooling to a temperature
of . The trapped molecular density of
cm is an order of magnitude greater than in the initial sub-Doppler
cooled sample. The trap lifetime of 750(40) ms is dominated by background gas
collisions.Comment: 5 pages, 5 figure
ALCHEMI Finds a “Shocking” Carbon Footprint in the Starburst Galaxy NGC 253
The centers of starburst galaxies may be characterized by a specific gas and ice chemistry due to their gas dynamics and the presence of various ice desorption mechanisms. This may result in a peculiar observable composition. We analyse the abundances of CO2, a reliable tracer of ice chemistry, from data collected as part of the Atacama Large Millimeter/submillimeter Array large program ALCHEMI, a wide-frequency spectral scan toward the starburst galaxy NGC 253 with an angular resolution of 1.″6. We constrain the CO2 abundances in the gas phase using its protonated form HOCO+. The distribution of HOCO+ is similar to that of methanol, which suggests that HOCO+ is indeed produced from the protonation of CO2 sublimated from ice. The HOCO+ fractional abundances are found to be (1-2)
7 10−9 at the outer part of the central molecular zone (CMZ), while they are lower (∼10−10) near the kinematic center. This peak fractional abundance at the outer CMZ is comparable to that in the Milky Way CMZ, and orders of magnitude higher than that in Galactic disk, star-forming regions. From the range of HOCO+/CO2 ratios suggested from chemical models, the gas-phase CO2 fractional abundance is estimated to be (1-20)
7 10−7 at the outer CMZ, and orders of magnitude lower near the center. We estimate the CO2 ice fractional abundances at the outer CMZ to be (2-5)
7 10−6 from the literature. A comparison between the ice and gas CO2 abundances suggests an efficient sublimation mechanism. This sublimation is attributed to large-scale shocks at the orbital intersections of the bar and CMZ
Energizing Star Formation: The Cosmic Ray Ionization Rate in NGC 253 Derived From ALCHEMI Measurements of HO and SO
The cosmic ray ionization rate (CRIR) is a key parameter in understanding the
physical and chemical processes in the interstellar medium. Cosmic rays are a
significant source of energy in star formation regions, which impacts the
physical and chemical processes which drive the formation of stars. Previous
studies of the circum-molecular zone (CMZ) of the starburst galaxy NGC 253 have
found evidence for a high CRIR value; times the average cosmic ray
ionization rate within the Milky Way. This is a broad constraint and one goal
of this study is to determine this value with much higher precision. We exploit
ALMA observations towards the central molecular zone of NGC 253 to measure the
CRIR. We first demonstrate that the abundance ratio of HO and SO is
strongly sensitive to the CRIR. We then combine chemical and radiative transfer
models with nested sampling to infer the gas properties and CRIR of several
star-forming regions in NGC 253 due to emission from their transitions. We find
that each of the four regions modelled has a CRIR in the range
s and that this result adequately fits the
abundances of other species that are believed to be sensitive to cosmic rays
including CH, HCO, HOC, and CO. From shock and PDR/XDR models, we
further find that neither UV/X-ray driven nor shock dominated chemistry are a
viable single alternative as none of these processes can adequately fit the
abundances of all of these species.Comment: 24 pages, 15 figures, accepted for publication in Ap
Tracing Interstellar Heating: An ALCHEMI Measurement of the HCN Isomers in NGC 253
We analyze HCN and HNC emission in the nearby starburst galaxy NGC 253 to investigate its effectiveness in tracing heating processes associated with star formation. This study uses multiple HCN and HNC rotational transitions observed using the Atacama Large Millimeter/submillimeter Array via the ALCHEMI Large Program. To understand the conditions and associated heating mechanisms within NGC 253\u27s dense gas, we employ Bayesian nested sampling techniques applied to chemical and radiative transfer models, which are constrained using our HCN and HNC measurements. We find that the volume density n H 2 and cosmic-ray ionization rate (CRIR) ζ are enhanced by about an order of magnitude in the galaxy’s central regions as compared to those further from the nucleus. In NGC 253\u27s central giant molecular clouds (GMCs), where observed HCN/HNC abundance ratios are the lowest, n ∼ 105.5 cm−3 and ζ ∼ 10−12 s−1 (greater than 104 times the average Galactic rate). We find a positive correlation in the association of both density and CRIR with the number of star formation-related heating sources (supernova remnants, H ii regions, and super hot cores) located in each GMC, as well as a correlation between CRIRs and supernova rates. Additionally, we see an anticorrelation between the HCN/HNC ratio and CRIR, indicating that this ratio will be lower in regions where ζ is higher. Though previous studies suggested HCN and HNC may reveal strong mechanical heating processes in NGC 253\u27s CMZ, we find cosmic-ray heating dominates the heating budget, and mechanical heating does not play a significant role in the HCN and HNC chemistry
Starburst Energy Feedback Seen through HCO+/HOC+Emission in NGC 253 from ALCHEMI
Molecular abundances are sensitive to the UV photon flux and cosmic-ray ionization rate. In starburst environments, the effects of high-energy photons and particles are expected to be stronger. We examine these astrochemical signatures through multiple transitions of HCO+ and its metastable isomer HOC+ in the center of the starburst galaxy NGC 253 using data from the Atacama Large Millimeter/submillimeter Array large program ALMA Comprehensive High-resolution Extragalactic Molecular inventory. The distribution of the HOC+(1-0) integrated intensity shows its association with "superbubbles,"cavities created either by supernovae or expanding H ii regions. The observed HCO+/HOC+ abundance ratios are ∼10-150, and the fractional abundance of HOC+ relative to H2 is ∼1.5 × 10-11-6 × 10-10, which implies that the HOC+ abundance in the center of NGC 253 is significantly higher than in quiescent spiral arm dark clouds in the Galaxy and the Galactic center clouds. Comparison with chemical models implies either an interstellar radiation field of G 0 ⪆ 103 if the maximum visual extinction is ⪆5, or a cosmic-ray ionization rate of ζ ⪆ 10-14 s-1 (3-4 orders of magnitude higher than that within clouds in the Galactic spiral arms) to reproduce the observed results. From the difference in formation routes of HOC+, we propose that a low-excitation line of HOC+ traces cosmic-ray dominated regions, while high-excitation lines trace photodissociation regions. Our results suggest that the interstellar medium in the center of NGC 253 is significantly affected by energy input from UV photons and cosmic rays, sources of energy feedback.N.H. acknowledges support
from JSPS KAKENHI grant No. JP21K03634. K.S. has been
supported by grants MOST 108-2112-M-001-015 and 109-
2112-M-001-020 from the Ministry of Science and Technology,
Taiwan. Y.N. is supported by the NAOJ ALMA Scientific
Research grant No. 2017-06B. V.M.R. and L.C. are funded by
the Comunidad de Madrid through the Atracción de Talento
Investigador (Doctores con experiencia) Grant (COOL: Cosmic
Origins Of Life; 2019-T1/TIC-15379)
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