scholarly journals The ALMA-PILS Survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293–2422 B

2018 ◽  
Vol 610 ◽  
pp. A54 ◽  
Author(s):  
M. V. Persson ◽  
J. K. Jørgensen ◽  
H. S. P. Müller ◽  
A. Coutens ◽  
E. F. van Dishoeck ◽  
...  
Keyword(s):  
Energy Levels ◽  
Excitation Temperature ◽  
Thermodynamical Equilibrium ◽  
Complex Molecules ◽  
Important Species ◽  
Chemical Models ◽  
Small Scales ◽  
Core Phase ◽  
Low Mass ◽  
First Time

Context.The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre- and protostellar cores. Formaldehyde is an important species in the formation of methanol and more complex molecules.Aims.Here, we aim to present the first study of formaldehyde deuteration on small scales around the prototypical low-mass protostar IRAS 16293–2422 using high spatial and spectral resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the excitation temperature, abundances and fractionation level of several formaldehyde isotopologues, including its deuterated forms.Methods.Excitation temperature and column densities of formaldehyde in the gas close to one of the components of the binary were constrained through modeling of optically thin lines assuming local thermodynamical equilibrium. The abundance ratios were compared to results from previous single dish observations, astrochemical models and local ISM values.Results.Numerous isotopologues of formaldehyde are detected, among them H2C17O, and D213CO for the first time in the ISM. The large range of upper energy levels covered by the HDCO lines help constrain the excitation temperature to 106 ± 13 K. Using the derived column densities, formaldehyde shows a deuterium fractionation of HDCO/H2CO = 6.5 ± 1%, D2CO/HDCO = 12.8–4.1+3.3%, and D2CO/H2CO = 0.6(4) ± 0.1%. The isotopic ratios derived are16O/18O = 805–79+43,18O/17O = 3.2–0.3+0.2, and12C/13C = 56–11+8.Conclusions.The HDCO/H2CO ratio is lower than that found in previous studies, highlighting the uncertainties involved in interpreting single dish observations of the inner warm regions. The D2CO/HDCO ratio is only slightly larger than the HDCO/H2CO ratio. This is consistent with formaldehyde forming in the ice as soon as CO has frozen onto the grains, with most of the deuteration happening toward the end of the prestellar core phase. A comparison with available time-dependent chemical models indicates that the source is in the early Class 0 stage.

scholarly journals Methanol formation in TW Hya and future prospects for detecting larger complex molecules in disks with ALMA

2017 ◽  
Vol 13 (S332) ◽  
pp. 395-402 ◽  
Author(s):  
Catherine Walsh ◽  
Shreyas Vissapragada ◽  
Harry McGee
Keyword(s):  
Gas Phase ◽  
Signal To Noise Ratio ◽  
Energy Levels ◽  
Complex Molecules ◽  
Rotational Spectra ◽  
Chemical Models ◽  
Methanol Formation ◽  
Peak Abundance ◽  
Abundance And Distribution ◽  
First Time

AbstractGas-phase methanol was recently detected in a protoplanetary disk for the first time with ALMA. The peak abundance and distribution of methanol observed in TW Hya differed from that predicted by chemical models. Here, the chemistry of methanol gas and ice is calculated using a physical model tailored for TW Hya with the aim to contrast the results with the recent detection in this source. New pathways for the formation of larger complex molecules (e.g., ethylene glycol) are included in an updated chemical model, as well as the fragmentation of methanol ice upon photodesorption. It is found that including fragmentation upon photodesorption improves the agreement between the peak abundance reached in the chemical models with that observed in TW Hya (∼10−11 with respect to H2); however, the model predicts that the peak in emission resides a factor of 2 − 3 farther out in the disk than the ALMA images. Reasons for the persistent differences in the gas-phase methanol distribution between models and the observations of TW Hya are discussed. These include the location of the ice reservoir which may coincide with the compact mm-dust disk (≲ 60 au) and sources of gas-phase methanol which have not yet been considered in models. The possibility of detecting larger molecules with ALMA is also explored. Calculations of the rotational spectra of complex molecules other than methanol using a parametric model constrained by the TW Hya observations suggest that the detection of individual emission lines of complex molecules with ALMA remains challenging. However, the signal-to-noise ratio can be enhanced via stacking of multiple transitions which have similar upper energy levels.

scholarly journals Characterizing the chemical pathways for water formation – a deep search for hydrogen peroxide

2014 ◽  
Vol 168 ◽  
pp. 349-367 ◽  
Author(s):  
Bérengère Parise ◽  
Per Bergman ◽  
Karl Menten
Keyword(s):  
Hydrogen Peroxide ◽  
Dark Clouds ◽  
Chemical Models ◽  
Upper Limits ◽  
Low Mass ◽  
And Shifts ◽  
First Time ◽  
Infrared Dark Clouds ◽  
Very High ◽  
High Column

In 2011, hydrogen peroxide (HOOH) was observed for the first time outside the solar system (Bergman et al., Astron. Astrophys., 2011, 531, L8). This detection appeared a posteriori to be quite natural, as HOOH is an intermediate product in the formation of water on the surface of dust grains. Following up on this detection, we present a search for HOOH in a diverse sample of sources in different environments, including low-mass protostars and regions with very high column densities, such as Infrared Dark Clouds (IRDCs). We do not detect the molecule in any other source than Oph A, and derive 3σ upper limits for the abundance of HOOH relative to H2 lower than that in Oph A for most sources. This result sheds a different light on our understanding of the detection of HOOH in Oph A, and shifts the question of why this source seems to be special. Therefore we rediscuss the detection of HOOH in Oph A, as well as the implications of the low abundance of HOOH, and its similarity with the case of O2. Our chemical models show that the production of HOOH is extremely sensitive to temperature, and is favored only in the range 20–30 K. The relatively high abundance of HOOH observed in Oph A suggests that the bulk of the material lies at a temperature in the range 20–30 K.

scholarly journals New Transition and Energy Levels of Three-Times Ionized Krypton (Kr IV)

Atoms ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 48
Author(s):  
M. Raineri ◽  
M. Gallardo ◽  
J. Reyna Almandos ◽  
A. G. Trigueiros ◽  
C. J. B. Pagan
Keyword(s):  
Transition Probabilities ◽  
Energy Levels ◽  
Pulsed Discharge ◽  
Core Polarization ◽  
Polarization Effects ◽  
Hartree Fock ◽  
Theta Pinch ◽  
New Energy ◽  
First Time

A capillary pulsed-discharge and a theta-pinch were used to record Kr spectra in the region of 330–4800 Å. A set of 168 transitions of these spectra were classified for the first time. We extended the analysis to twenty-five new energy levels belonging to 3s23p24d, 3s23p25d even configurations. We calculated weighted transition probabilities (gA) for all of the experimentally observed lines and lifetimes for new energy levels using a relativistic Hartree–Fock method, including core-polarization effects.

scholarly journals On N-body simulations of globular cluster streams

2021 ◽  
Vol 504 (1) ◽  
pp. 648-653
Author(s):  
Nilanjan Banik ◽  
Jo Bovy
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Analytical Models ◽  
Numerical Density ◽  
Stellar Streams ◽  
Small Scales ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Stream Density ◽  
Tidal Streams

ABSTRACT Stellar tidal streams are sensitive tracers of the properties of the gravitational potential in which they orbit and detailed observations of their density structure can be used to place stringent constraints on fluctuations in the potential caused by, e.g. the expected populations of dark matter subhaloes in the standard cold dark matter (CDM) paradigm. Simulations of the evolution of stellar streams in live N-body haloes without low-mass dark matter subhaloes, however, indicate that streams exhibit significant perturbations on small scales even in the absence of substructure. Here, we demonstrate, using high-resolution N-body simulations combined with sophisticated semi-analytical and simple analytical models, that the mass resolutions of 104–$10^5\, \rm {M}_{\odot }$ commonly used to perform such simulations cause spurious stream density variations with a similar magnitude on large scales as those expected from a CDM-like subhalo population and an order of magnitude larger on small, yet observable, scales. We estimate that mass resolutions of ${\approx}100\, \rm {M}_{\odot }$ (${\approx}1\, \rm {M}_{\odot }$) are necessary for spurious, numerical density variations to be well below the CDM subhalo expectation on large (small) scales. That streams are sensitive to a simulation’s particle mass down to such small masses indicates that streams are sensitive to dark matter clustering down to these low masses if a significant fraction of the dark matter is clustered or concentrated in this way, for example, in MACHO models with masses of 10–$100\, \rm {M}_{\odot }$.

scholarly journals Extended analysis of Xe VII and Xe VIII

2017 ◽  
Vol 95 (9) ◽  
pp. 805-810 ◽  
Author(s):  
M. Raineri ◽  
M. Gallardo ◽  
J. Reyna Almandos ◽  
C.J.B. Pagan ◽  
R. Sarmiento
Keyword(s):  
Light Source ◽  
Energy Levels ◽  
Excited Configuration ◽  
Pulsed Discharge ◽  
Hartree Fock ◽  
The Core ◽  
New Energy ◽  
Extended Analysis ◽  
First Time ◽  
Atomic Parameters

A pulsed discharge light source to study the six and seven times ionized xenon spectra in the 419–4642 Å region was used. A set of 40 transitions of Xe VII and 25 transitions of Xe VIII were classified for the first time. We revised the values for the previously known energy levels and extended the analysis for Xe VII to 10 new energy levels belonging to 5s6d, 5s7s and 5s7p, 4d95s25p even and odd configurations, respectively. Seven new energy levels of the core excited configuration 4d95s5d of Xe VIII are presented. For the prediction of the atomic parameters, energy levels, and transition, relativistic Hartree–Fock calculations were used.

scholarly journals Visible AO Observations at Halpha for Accreting Young Planets

2013 ◽  
Vol 8 (S299) ◽  
pp. 32-33
Author(s):  
L.M. Close ◽  
K. Follette ◽  
J.R. Males ◽  
K. Morzinski ◽  
T.J. Rodigas ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Binary Stars ◽  
Optical Resolution ◽  
Ccd Camera ◽  
Short Exposure ◽  
Low Mass ◽  
Orion Trapezium ◽  
First Time ◽  
Adaptive Optics System ◽  
Very High

AbstractWe utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high-resolution science in the visible with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.5–0.7″) we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r' (0.63μm) images are slightly coarser at FWHM = 23-29 mas (Strehl ~ 28%) with bright (R < 9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (~ 1 Myr) Orion Trapezium θ1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary θ1 Ori C1C2 was easily resolved in non-interferometric images for the first time. Relative positions of the bright trapezium binary stars were measured with ~ 0.6–5 mas accuracy. In the second commissioning run we were able to correct 378 modes and achieved good contrasts (Strehl>20% on young transition disks at Hα). We discuss the contrasts achieved at Hα and the possibility of detecting low mass (~ 1–5 Mjup) planets (past 5AU) with our new SAPPHIRES survey with MagAO at Hα.

scholarly journals GEM-Based Detectors for Direct Detection of Low-Mass WIMP, Solar Axions and Narrow Resonances (Quarks)

2021 ◽  
Author(s):  
Victor Parusov ◽  
Boris Ovchinnikov
Keyword(s):  
Direct Detection ◽  
Detection System ◽  
Beta Particle ◽  
Gaseous Mixtures ◽  
Low Mass ◽  
Nonzero Spin ◽  
Time Projection ◽  
First Time ◽  
Solar Axions ◽  
Low Mass Wimp

Gas electron multipliers (GEMs) with wire (WGEMs) or metal electrodes (MGEMs), which don&rsquo;t use any plastic insulators between electrodes are created. The chambers containing MGEMs (WGEMs) with pin-anodes are proposed as detectors for searching of spin-dependent interactions between Dark Matter (DM) particles and gases with nonzero-spin nuclei (H2, D2, 3He, 21Ne, CF4, CH4, etc.). In this paper, we present a review of such chambers. For investigation of the gas mixtures Ne+10%H2, H2 (D2) +3ppmTMAE, the chamber containing WGEM with pin-anode detection system was constructed. In this paper we present the results of an experimental study of these gaseous mixtures exited by an &alpha; - source. Mixture of Ar + 40 ppm C2H4 and mixture 50% Xe + 50%CF4 have been investigated. The spatial distributions of photoelectron clouds produced by primary scintillations on &alpha;- and &beta;-particle tracks, as well as the distributions of photoelectron clouds due to photons from avalanches at the pin-anode, have been measured for the first time. In our experiments as another filling of the chambers for search of low-mas WIMP (&lt;10 GeV/c2), solar neutrino and solar axions with spin-dependent interaction we propose to use the mixtures: D2 + 3ppmTMAE, 3He + 3%CH4, 21Ne + 10%H2, at pressure 10-17 bar. And in our experiment with liquid gases is used the mixtures with 19F (LAr + CF4, LXe + CF4) and mixture LCH4 + 40ppm TMAE. The time projection chamber (TPC) with the mixture D2 + 3ppmTMAE filling allow to search of spin-dependent interactions of solar axions and deuterium. As well as we present the detecting systems for search of narrow pp-resonances (quarks) in accelerators experiments.

LOW-SPIN STATES OF 76Se EXCITED IN 76Br(β++EC)76Se DECAY

2004 ◽  
Vol 13 (05) ◽  
pp. 933-947
Author(s):  
YAN LI ◽  
SHUIFA SHEN ◽  
WENDA HUANG ◽  
SHUANGHUI SHI ◽  
JIAHUI GU ◽  
...  
Keyword(s):  
High Resolution ◽  
Energy Levels ◽  
Spin States ◽  
Hpge Detectors ◽  
New Energy ◽  
Coincidence Mode ◽  
Γ Rays ◽  
First Time

The decay of bromine-76 was studied using high resolution HpGe detectors in singles and coincidence mode. Bromine-76 was produced via two reactions: 75 As (α,3 n )76 Br and 76 Se ( p , n )76 Br . The results of these experiments verified the previously reported levels of 76 Se . In addition to the previously described transitions and levels, 37 new γ-rays and 15 new energy levels were found for the first time.

Immature stages, host plants and natural enemies of Henosepilachna implicata (Mulsant) (Coleoptera: Coccinellidae) with DNA sequence data and a new synonym and notes on some Indian species of Epilachnini

Zootaxa ◽  
2021 ◽  
Vol 4970 (3) ◽  
pp. 533-546
Author(s):  
J. POORANI ◽  
R. G. BOOTH ◽  
R. GANDHI GRACY ◽  
C. ANURADHA ◽  
R. THANIGAIRAJ ◽  
...  
Keyword(s):  
Dna Sequence ◽  
Natural Enemies ◽  
Host Plants ◽  
Sequence Data ◽  
Indian Species ◽  
Life Stages ◽  
Important Species ◽  
Dna Sequence Data ◽  
New Synonym ◽  
First Time

Life stages of Henosepilachna implicata (Mulsant), an economically important species of Epilachnini in India, are documented and illustrated. Mitochondrial DNA sequence data is provided for the first time for H. implicata with additional details on its host plants, distribution, and natural enemies. Its similarities and differences with other common pestiferous Henosepilachna spp. in India such as H. vigintioctopunctata (F.), H. septima (Dieke) and H. pusillanima (Mulsant) are discussed. Epilachna circularis Korschefsky, 1933 is found to be conspecific with H. implicata and is reduced to a junior synonym of the latter (new synonym). Notes are given on the distribution and natural enemies of some other species of Epilachnini of the Indian region.  

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