scholarly journals Deep search for hydrogen peroxide toward pre- and protostellar objects

2020 ◽  
Vol 636 ◽  
pp. A114
Author(s):  
G. W. Fuchs ◽  
D. Witsch ◽  
D. Herberth ◽  
M. Kempkes ◽  
B. Stanclik ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Solid State ◽  
Water Reservoir ◽  
Reaction Network ◽  
Reaction Scheme ◽  
Young Stellar Objects ◽  
Model Parameters ◽  
Stellar Objects ◽  
Additional Information ◽  
Water Formation

Context. In the laboratory, hydrogen peroxide (HOOH) was proven to be an intermediate product in the solid-state reaction scheme that leads to the formation of water on icy dust grains. When HOOH desorbs from the icy grains, it can be detected in the gas phase. In combination with water detections, it may provide additional information on the water reaction network. Hydrogen peroxide has previously been found toward ρ Oph A. However, further searches for this molecule in other sources failed. Hydrogen peroxide plays a fundamental role in the understanding of solid-state water formation and the overall water reservoir in young stellar objects (YSOs). Without further HOOH detections, it is difficult to assess and develop suitable chemical models that properly take into account the formation of water on icy surfaces. Aims. The objective of this work is to identify HOOH in YSOs and thereby constrain the grain surface water formation hypothesis. Methods. Using an astrochemical model based on previous work in combination with a physical model of YSOs, the sources R CrA-IRS 5A, NGC C1333-IRAS 2A, L1551-IRS 5, and L1544 were identified as suitable candidates for an HOOH detection. Long integration times on the APEX 12 m and IRAM 30 m telescopes were applied to search for HOOH signatures in these sources. Results. None of the four sources under investigation showed convincing spectral signatures of HOOH. The upper limit for HOOH abundance based on the noise level at the frequency positions of this molecule for the source R CrA-IRS 5A was close to the predicted value. For NGC 1333-IRAS 2A, L1544, and L1551-IRS 5, the model overestimated the hydrogen peroxide abundances. Conclusions. HOOH remains an elusive molecule. With only one secure cosmic HOOH source detected so far, namely ρ Oph A, the chemical model parameters for this molecule cannot be sufficiently well determined or confirmed in existing models. Possible reasons for the nondetections of HOOH are discussed.

scholarly journals Solid State DIBs

2013 ◽  
Vol 9 (S297) ◽  
pp. 359-363
Author(s):  
H. Linnartz
Keyword(s):  
Solid State ◽  
Low Temperatures ◽  
Molecular Hydrogen ◽  
Experimental Approach ◽  
Amorphous Solid ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Dark Clouds ◽  
Diffuse Interstellar Bands ◽  
Interstellar Ice

AbstractThe diffuse interstellar bands are not due to solid state species. However, under the explicit assumption that DIB carriers survive the transfer from translucent to dark clouds, it is expected that for the low temperatures in the dense interstellar medium also DIB carriers accrete onto dust grains. Like all other molecules, apart from molecular hydrogen, they will get embedded in an ice matrix that largely consists of amorphous solid water. This offers - in principle - a tool to search for DIBs in complete different environments, both in space (i.e., towards embedded young stellar objects) and in the laboratory, namely in the solid state simulating interstellar ice analogues. Currently experiments are ongoing in the Sackler Laboratory for Astrophysics at Leiden Observatory to record optical ice spectra of potential DIB carriers. For this a new experimental approach has been developed. Its performance and potential are discussed.

scholarly journals Simulating the circumstellar H2CO and CH3OH chemistry of young stellar objects using a spherical physical-chemical model

2020 ◽  
Vol 639 ◽  
pp. A143
Author(s):  
G. W. Fuchs ◽  
D. Witsch ◽  
D. Herberth ◽  
M. Kempkes ◽  
B. Stanclik ◽  
...  
Keyword(s):  
Solid State ◽  
Temperature Gradient ◽  
Gas Phase ◽  
Solid State Reactions ◽  
Young Stellar Objects ◽  
Chemical Model ◽  
Number Density ◽  
Stellar Objects ◽  
Physical Chemical ◽  
Class 1

Context. Young stellar objects (YSOs) and their environments are generally geometrically and dynamically challenging to model, and the corresponding chemistry is often dominated by regions in non-thermal equilibrium. In addition, modern astrochemical models have to consider not only gas-phase reactions, but also solid-state reactions on icy dust grains. Solving the geometrical, physical, and chemical boundary conditions simultaneously requires a high computational effort and still runs the risk of false predictions due to the intrinsically non-linear effects that can occur. As a first step, solving problems of reduced complexity is helpful to guide more sophisticated approaches. Aims. The objective of this work is to test a model that uses shell-like structures (i.e., assuming a power-law number density and temperature gradient of the environment surrounding the YSO) to approximate the geometry and physical structure of YSOs, that in turn utilizes an advanced chemical model that includes gas-phase and solid-state reactions to model the chemical abundances of key species. A special focus is set on formaldehyde (H2CO) and methanol (CH3OH) as these molecules can be traced in the gas phase but are produced on icy dust grains. Furthermore, this kind of molecule is believed to be key to understanding the abundance of more complex species. We compare the influence of the geometry of the object on the molecular abundances with the effect induced by its chemistry. Methods. We set up a model that combines a grain-gas phase chemical model with a physical model of YSOs. The model ignores jets, shocks, and external radiation fields and concentrates on the physical conditions of spherically symmetric YSOs with a density and temperature gradient derived from available spectral energy distribution observations in the infrared. In addition, new observational data are presented using the APEX 12 m and the IRAM 30 m telescopes. Formaldehyde and methanol transitions have been searched for in three YSOs (R CrA-IRS 5A, C1333-IRAS 2A, and L1551-IRS 5) that can be categorized as Class 0 and Class 1 objects, and in the pre-stellar core L1544. The observed abundances of H2CO and CH3OH are compared with those calculated by the spherical physical-chemical model. Results. Compared to a standard “ρ and T constant” model, i.e., a homogeneous (flat) density and temperature distribution, using number density and temperature gradients results in reduced abundances for the CO hydrogenation products formaldehyde and methanol. However, this geometric effect is generally not large, and depends on the source and on the molecular species under investigation. Although the current model uses simplified geometric assumptions the observed abundances of H2CO and CH3OH are well reproduced for the quiescent Class 1 object R CrA-IRS 5A. Our model tends to overestimate formaldehyde and methanol abundances for sources in early evolutionary stages, like the pre-stellar core L1544 or NGC 1333-IRS 2A (Class 0). Observational results on hydrogen peroxide and water that have also been predicted by our model are discussed elsewhere.

scholarly journals Precursors of complex organic molecules: NH3 and CH3OH in the ices surrounding low-mass protostars

2008 ◽  
Vol 4 (S251) ◽  
pp. 105-110 ◽  
Author(s):  
Sandrine Bottinelli ◽  
Adwin C. A. Boogert ◽  
Ewine F. van Dishoeck ◽  
Martha Beckwith ◽  
Jordy Bouwman ◽  
...  
Keyword(s):  
Solid State ◽  
Gas Phase ◽  
Organic Molecules ◽  
High Sensitivity ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Space Telescope ◽  
Low Mass ◽  
Complex Organic

AbstractNH3 and CH3OH are key molecules in the chemical networks leading to the formation of complex N- and O-bearing organic molecules. However, despite a number of recent studies, there is still a lot to learn about their abundances in the solid state and how they relate to those of other N/O-bearing organic molecules or to NH3 and CH3OH abundances in the gas phase. This is particularly true in the case of low-mass young stellar objects (YSOs), for which only the recent advent of the Spitzer Space Telescope has allowed high sensitivity observations of the ices in their enveloppes. We present a combined study of Spitzer data (obtained within the Legacy program “From Molecular Cores to Planet-Forming Disks”, c2d) and laboratory spectra, leading to the detections of NH3 and CH3OH in the ices of low-mass protostars. We investigate correlations with other ice features and conclude with prospects on further studies linking these two precursors of complex organic molecules with their gas-phase products.

A Near-Infrared Search for Companions around Very Low Luminosity Young Stellar Objects in Taurus

1999 ◽  
Vol 117 (3) ◽  
pp. 1471-1484 ◽  
Author(s):  
Yoichi Itoh ◽  
Motohide Tamura ◽  
Tadashi Nakajima
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Stellar Objects

scholarly journals The Observational Evidence for Accretion

1997 ◽  
Vol 182 ◽  
pp. 391-405 ◽  
Author(s):  
Lee Hartmann
Keyword(s):  
Large Range ◽  
Observational Evidence ◽  
Young Stars ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
T Tauri ◽  
Accretion Rates ◽  
Low Mass ◽  
Stellar Magnetospheres ◽  
Mass Ejection

Outflows from low-mass young stellar objects are thought to draw upon the energy released by accretion onto T Tauri stars. I briefly summarize the evidence for this accretion and outline present estimates of mass accretion rates. Young stars show a very large range of accretion rates, and this has important implications for both mass ejection and for the structure of stellar magnetospheres which may truncate T Tauri disks.

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

scholarly journals Effect of hydrogen peroxide on natural phytoplankton and bacterioplankton in a drinking water reservoir: Mesocosm-scale study

2021 ◽  
pp. 117069
Author(s):  
Allan A. Santos ◽  
Dayvson O. Guedes ◽  
Mário U.G. Barros ◽  
Samylla Oliveira ◽  
Ana B.F. Pacheco ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Drinking Water ◽  
Water Reservoir ◽  
Drinking Water Reservoir ◽  
Natural Phytoplankton

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

scholarly journals Searching for young stellar objects through SEDs by machine learning

2021 ◽  
pp. 100470
Author(s):  
Y.-L. Chiu ◽  
C.-T. Ho ◽  
D.-W. Wang ◽  
S.-P. Lai
Keyword(s):  
Machine Learning ◽  
Young Stellar Objects ◽  
Stellar Objects
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