Determining the full satellite population of a Milky Way-mass halo in a highly resolved cosmological hydrodynamic simulation

We investigate the formation of the satellite galaxy population of a Milky Way-mass halo in a very highly resolved magneto-hydrodynamic cosmological zoom-in simulation (baryonic mass resolution mb = 800 $\rm M_{\odot }$). We show that the properties of the central star-forming galaxy, such as the radial stellar surface density profile and star formation history, are: i) robust to stochastic variations associated with the so-called ‘Butterfly Effect’; and ii) well converged over 3.5 orders of magnitude in mass resolution. We find that there are approximately five times as many satellite galaxies at this high resolution compared to a standard ($m_b\sim 10^{4-5}\, \rm M_{\odot }$) resolution simulation of the same system. This is primarily because 2/3rds of the high resolution satellites do not form at standard resolution. A smaller fraction (1/6th) of the satellites present at high resolution form and disrupt at standard resolution; these objects are preferentially low-mass satellites on intermediate- to low-eccentricity orbits with impact parameters ≲ 30 kpc. As a result, the radial distribution of satellites becomes substantially more centrally concentrated at higher resolution, in better agreement with recent observations of satellites around Milky Way-mass haloes. Finally, we show that our galaxy formation model successfully forms ultra-faint galaxies and reproduces the stellar velocity dispersion, half-light radii, and V-band luminosities of observed Milky Way and Local Group dwarf galaxies across 6 orders of magnitude in luminosity (103-$10^{9}\, \rm L_{\odot }$).

A Miniature Four-Channel Ion Trap Array Based on Non-silicon MEMS Technology

With the increasing application field, a higher requirement is put forward for the mass spectrometer. The reduction in size will inevitably cause a loss of precision; therefore, it is necessary to develop a high-performance miniature mass spectrometer. Based on the researches of rectangular ion trap, the relationship between mass resolution and structural parameters of the ion trap array was analyzed by further simulation. The results indicate that, considering the balance of mass resolution and extraction efficiency, the preferable values for the field radius of exit direction y0 and ion exit slot width s0 are 1.61 mm and 200 μm, respectively. Afterwards, a miniature four-channel ion trap array (MFITA) was fabricated, by using MEMS and laser etching technology, and mass spectrometry experiments were carried out to demonstrate its performance. The mass resolution of butyl diacetate with m/z = 230 can reach 324. In addition, the consistency of four channels is verified within the error tolerance, by analyzing air samples. Our work can prove the correctness of the structural design and the feasibility of MEMS preparation for MFITA, which will bring meaningful guidance for its future development and optimization.

AccuCor2 Isotope Natural Abundance Correction for Dual-Isotope Tracer Experiments

Stable isotope labeling techniques have been widely applied in the field of metabolomics and proteomics. Before the measured mass spectrum data can be used for quantitative analysis, it must be accurately corrected for isotope natural abundance and tracer isotopic impurity. Despite the increasing popularity of dual-isotope tracing strategy such as ¹³C-¹⁵N or ¹³C-²H, there is no accurate tool for correcting isotope natural abundance for such experiments. Here, we present AccuCor2 as an R-based tool to perform the correction for ¹³C-¹⁵N or ¹³C-²H labeling experiments. Our results show that the dual-isotope experiments often require a mass resolution that is high enough to resolve ¹³C and ¹⁵N or ¹³C and ²H.Otherwise the labeling pattern is not solvable. However, this mass resolution may not be sufficiently high to resolve other non-tracer elements such as oxygen or sulfur from the tracer elements. Therefore, we design AccuCor2 to perform the correction based on the actual mass resolution of the measurements. Using both simulated and experimental data, we show that AccuCor2 performs accurate and resolution dependent correction for dual-isotope tracer data.

AccuCor2 Isotope Natural Abundance Correction for Dual-Isotope Tracer Experiments

Stable isotope labeling techniques have been widely applied in the field of metabolomics and proteomics. Before the measured mass spectrum data can be used for quantitative analysis, it must be accurately corrected for isotope natural abundance and tracer isotopic impurity. Despite the increasing popularity of dual-isotope tracing strategy such as ¹³C-¹⁵N or ¹³C-²H, there is no accurate tool for correcting isotope natural abundance for such experiments. Here, we present AccuCor2 as an R-based tool to perform the correction for ¹³C-¹⁵N or ¹³C-²H labeling experiments. Our results show that the dual-isotope experiments often require a mass resolution that is high enough to resolve ¹³C and ¹⁵N or ¹³C and ²H.Otherwise the labeling pattern is not solvable. However, this mass resolution may not be sufficiently high to resolve other non-tracer elements such as oxygen or sulfur from the tracer elements. Therefore, we design AccuCor2 to perform the correction based on the actual mass resolution of the measurements. Using both simulated and experimental data, we show that AccuCor2 performs accurate and resolution dependent correction for dual-isotope tracer data.

The tidal evolution of dark matter substructure – II. The impact of artificial disruption on subhalo mass functions and radial profiles

Several recent studies have indicated that artificial subhalo disruption (the spontaneous, non-physical disintegration of a subhalo) remains prevalent in state-of-the-art dark matter-only cosmological simulations. In order to quantify the impact of disruption on the inferred subhalo demographics, we augment the semi-analytical SatGen dynamical subhalo evolution model with an improved treatment of tidal stripping that is calibrated using the DASH database of idealized high-resolution simulations of subhalo evolution, which are free from artificial disruption. We also develop a model of artificial disruption that reproduces the statistical properties of disruption in the Bolshoi simulation. Using this framework, we predict subhalo mass functions (SHMFs), number density profiles, and substructure mass fractions and study how these quantities are impacted by artificial disruption and mass resolution limits. We find that artificial disruption affects these quantities at the $10-20\%$ level, ameliorating previous concerns that it may suppress the SHMF by as much as a factor of two. We demonstrate that semi-analytical substructure modeling must include orbit integration in order to properly account for splashback haloes, which make up roughly half of the subhalo population. We show that the resolution limit of N-body simulations, rather than artificial disruption, is the primary cause of the radial bias in subhalo number density found in dark matter-only simulations. Hence, we conclude that the mass resolution remains the primary limitation of using such simulations to study subhaloes. Our model provides a fast, flexible, and accurate alternative to studying substructure statistics in the absence of both numerical resolution limits and artificial disruption.

OLYMPIA - a compact laboratory Orbitrap-based high-resolution mass spectrometer laboratory set-up: Performance studies for gas composition measurement in analogues of planetary environments

<p>In situ composition measurements at Saturn and its moons (Cassini-Huygens<sup>1,2</sup>) and at comet 67P/Churyumov-Gerasimenko (Rosetta<sup>3,4</sup>) unveiled the complexity of the atmospheric chemical composition and high abundance of organic compounds in the environments of Solar System bodies. The deciphering of the measurements, obtained by current state-of-the-art instruments, to obtain the composition of complex gas mixtures that include polyatomic molecules and volatile organic compounds (VOCs) often requires having recourse to instrument response modeling supplemented by theoretical chemical models.</p><p>One of the limitations in currently flown mass spectrometers is their limited mass resolving power. High mass-resolving power offers the capability to identify unambiguously almost all complex organic compounds. Such technique offers identification of almost all complex organic compounds without application of complementary separation techniques, e.g. chromatography, spectroscopy or collision induced dissociation. A new generation of space mass spectrometers under development (MASPEX<sup>5</sup>, MULTUM<sup>6</sup>, CORALS<sup>7</sup>, CRATER<sup>7</sup>, among others), aims at reaching mass resolution of > 50 000. CORALS and CRATER are Orbitrap-based instruments using CosmOrbitrap elements.</p><p>In collaboration with J. Herovsky institute, the Laboratoire de Physique et de Chimie de l'Environnement et de l'Espace (LPC2E) has developed a new laboratory test-bench based on the Orbitrap™ technology OLYMPIA (Orbitrap anaLYseur MultiPle IonisAtion) to evaluate several space applications of an Orbitrap-based space instrument using different ionization techniques. OLYMPIA is a compact, transportable set-up and is intended to be used as a stand-alone device (currently with an EI ionization source), but later intended to be coupled to different sources of ions. The next step in the next few months is to couple it with the LLILBID set-up in Berlin<sup>8</sup>.</p><p>OLYMPIA is currently directly coupled with a first prototype of a compact electron impact ionization source. A single shot provides a useful signal duration of 200-250ms second before it decays to the noise level, and provide mass resolution for Kr ion isotopes of the order of 30 000 and on C<sub>2</sub>H<sub>4</sub> on fragments of the order of 40 000. Kr is mostly being used to characterize the isotopic measurement capability of OLYMPIA and mixtures of C<sub>2</sub>H<sub>4</sub>, CO and N<sub>2</sub>gases in different proportions.  In this presentation we concentrate on the capability to detect low ethylene lighter VOC concentration in different mixtures of CO and N<sub>2</sub>. Sensitivity of the instrument is sufficient to detect traces of the carbon dioxide gas in mixture with molecular nitrogen abundant in less than 1% volume ratio.</p><p><strong>1</strong> Waite, J. H. et al. Space Sci. Rev. 114, 113–231 (2004)</p><p><strong>2</strong> Coates, A. J. et al. Geophys. Res. Lett. 34, (2007)</p><p><strong>3</strong> Balsiger, H. et al. Space Sci. Rev. 128, 745–801 (2007)</p><p><strong>4</strong> Le Roy, L. et al. A&A 583, (2015)</p><p><strong>5</strong> Brockwell, T. G. et al. in 2016 IEEE Aerospace Conference 1–17 (2016)</p><p><strong>6</strong> Shimma, S. et al. Anal. Chem. 82, 8456–8463 (2010)</p><p><strong>7</strong> Arevalo Jr, R. et al. Rapid Commun. Mass Spectrom. 32, 1875–1886 (2018)</p><p><strong>8</strong> Klenner, F. et al. Astrobiology 20, 179–189 (2019)</p>

Development of a Triple-Reflection Compact Time-Of-Flight Mass Spectrometer for Lunar Polar Exploration

<p>In order to investigate the presence (and amount) of the water (ice) molecules in the regolith 1 to 1.5 m below the lunar surface, a compact neutral particle mass spectrometer is under development. This neutral particle mass spectrometer is designed to install on a Moon rover, and it will perform mass analysis of neutral gas generated in the heating chamber. This mass spectrometer not only aims to measure the amount of water molecules included in the lunar regolith but also identify the atoms, molecules and their isotopes up to mass number 200 with mass resolution as high as 100.</p><p>The mass spectrometer under development is a reflectron that is a Time-Of-Flight mass spectrometer. A standard reflectron consists of an ion source, ion acceleration part, free flight part, ion reflection part and an ion detector. Ionized neutral particles are accelerated in the two-stage ion acceleration part by a pulsed high voltage whose pulse timing is used as a start signal. The accelerated ions enter into the free flight part and reflected in the single-stage ion reflection part. Reflected ions again fly through the free flight part and detected by a detector. Ion mass is determined by the time difference between the start signal and the particle detection.</p><p>In order to increase the mass resolution as much as possible within the allocated volume, we have decided to modify the standard reflectron by adding a second reflector that enables triple reflections and doubles the flight length. This newly designed triple-reflection TOF mass spectrometer can be operated also as a standard reflectron by changing the electric field configuration. Since the triple-reflection reduces the detection efficiency while increasing the mass resolution, the single reflection mode is used as a complementary mode where the detection efficiency is higher while the mass resolution is lower.</p><p>  </p>

The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies

CEMP-no stars, a subset of carbon enhanced metal poor (CEMP) stars ($\rm [C/Fe]\ge 0.7$ and $\rm [Fe/H]\lesssim -1$) have been discovered in ultra-faint dwarf (UFD) galaxies, with Mvir ≈ 108 M⊙ and M* ≈ 103 − 104 M⊙ at z = 0, as well as in the halo of the Milky Way (MW). These CEMP-no stars are local fossils that may reflect the properties of the first (Pop III) and second (Pop II) generation of stars. However, cosmological simulations have struggled to reproduce the observed level of carbon enhancement of the known CEMP-no stars. Here we present new cosmological hydrodynamic zoom-in simulations of isolated UFDs that achieve a gas mass resolution of mgas ≈ 60 M⊙. We include enrichment from Pop III faint supernovae (SNe), with ESN = 0.6 × 1051 erg, to understand the origin of CEMP-no stars. We confirm that Pop III and Pop II stars are mainly responsible for the formation of CEMP and C-normal stars respectively. New to this study, we find that a majority of CEMP-no stars in the observed UFDs and the MW halo can be explained by Pop III SNe with normal explosion energy (ESN = 1.2 × 1051 erg) and Pop II enrichment, but faint SNe might also be needed to produce CEMP-no stars with $\rm [C/Fe]\gtrsim 2$, corresponding to the absolute carbon abundance of $\rm A(C)\gtrsim 6.0$. Furthermore, we find that while we create CEMP-no stars with high carbon ratio $\rm [C/Fe]\approx 3-4$, by adopting faint SNe, it is still challenging to reproduce CEMP-no stars with extreme level of carbon abundance of $\rm A(C)\approx 7.0-7.5$, observed both in the MW halo and UFDs.