Quantifying Scatter in Galaxy Formation at the Lowest Masses

We predict the stellar mass–halo mass (SMHM) relationship for dwarf galaxies, using simulated galaxies with peak halo masses of M peak = 1011 M ⊙ down into the ultra-faint dwarf range to M peak = 107 M ⊙. Our simulated dwarfs have stellar masses of M star = 790 M ⊙ to 8.2 × 108 M ⊙, with corresponding V-band magnitudes from −2 to −18.5. For M peak > 1010 M ⊙, the simulated SMHM relationship agrees with literature determinations, including exhibiting a small scatter of 0.3 dex. However, the scatter in the SMHM relation increases for lower-mass halos. We first present results for well-resolved halos that contain a simulated stellar population, but recognize that whether a halo hosts a galaxy is inherently mass resolution dependent. We thus adopt a probabilistic model to populate “dark” halos below our resolution limit to predict an “intrinsic” slope and scatter for the SMHM relation. We fit linearly growing log-normal scatter in stellar mass, which grows to more than 1 dex at M peak = 108 M ⊙. At the faintest end of the SMHM relation probed by our simulations, a galaxy cannot be assigned a unique halo mass based solely on its luminosity. Instead, we provide a formula to stochastically populate low-mass halos following our results. Finally, we show that our growing log-normal scatter steepens the faint-end slope of the predicted stellar mass function.

Chromites in Ordinary chondrite fusion crusts

<p>We studied 5 fall Ordinary Chondrites of different groups (H4, H5, LL5, LL6, L3.6) and an Antarctic meteorite (H5), in order to investigate possible compositional differences between the chromites present in the bulk and the chromites formed within the fusion crust. We report here the composition of about 50 chromites measured within the bulk and 70 chromites found in the crust.</p> <p>Chromites found in the bulk are usually anhedral and relatively large in size (several tens of micrometers), whereas chromites formed within the crust are consistently smaller (few micrometers in size) and can display anhedral, or subhedral to euhedral habit.</p> <p>The Mg# and Al# determined for all the chromites found in the bulk show a fair agreement with data reported in the literature for chromite compositions in ordinary chondrites (Bunch et al., 1967; Ramdohr, 1967; Rubin, 2003; Wlotzka, 2005), which display a small scatter of the Al# (ca.0.13±0.025) and a large variation of the Mg# (from 0.05 to 0.30).</p> <p>When compared with the ones found in the bulk, chromites found within the fusion crusts generally exhibit similar values of the Al#; however, they display a much larger scatter of the Mg# and, usually, also larger average Mg# (up to 0.65) than their conterparts in the bulk.</p> <p>Chromite in the fusion crusts are often associated to magnetite dendrites made up by magnetite octahedral crystals 200-400 nanometers wide; occasionally, other spinel group minerals can be found, as magnesiochromites and magnesioferrites. In most of the samples studied, several chromite crystals are mantled by magnetite crystals, whereas no magnetite crystal has been found mantled by chromites. Textural data so far collected suggest a crystallization sequence in the fusion crust: Olivine, Chromite, Magnetite.</p> <p> </p> <p><strong>References:</strong></p> <p>Bunch T.E., Keil K. and Snetsinger K.G. (1967). Chromite composition in relation to chemistry and texture of ordinary chondrites. Geochimica et Cosmochimica Acta, <strong>31</strong>, 1569-1582.</p> <p>Ramdohr P. (1967). Chromite and chromite chondrules in meteorites-I. Geochimica et Cosmochimica Acta, <strong>31</strong>, 1961-1967.</p> <p>Rubin A.E. (2003). Chromite-Plagioclase assemblages as a new shock indicator; implications for the shock and thermal histories of ordinary chondrites. Geochimica et Cosmochimica Acta, <strong>67</strong>, 2695–2709.</p> <p>Wlotzka F. (2005) Cr spinel and chromite as petrogenetic indicators in ordinary chondrites: Equilibration temperatures of petrologic types 3.7 to 6. Meteoritics and Planetary Science, <strong>40</strong>, 1673-1702</p> <p> </p>

Variations of stable oxygen and hydrogen isotopes in the pingo ice core, south of the Gydan Peninsula

The vertical isotopic profile of the pingo Messoyakha-1 (coordinates: 68°30′32″ N, 79°59′53″ E) ice core, obtained in the south of the Gydan Peninsula in the Middle Messoyakha swell. There is no significant variations of the isotopic composition of pingo ice core: δ18О values vary from -14.98 to -16.60‰, δ2Н values vary from -117.9 to -12.8. This small scatter of values is probably the result of intense heaving and rather rapid formation of the pingo. Basing on the features of the pingo, it can be assumed that initially there was a lake of 0.5 km length and 0.3 km width in this site. Then, as a result of water draining to a nearby river, the lake began to dry out and alas, which occupies most of the primary lake area, was formed. Pingo arose during the freezing of the alas under its gradual drying.

Polytropic state of the intracluster medium in the X-COP cluster sample

Aims. In this work, we have investigated the relation between the radially resolved thermodynamic quantities of the intracluster medium in the X-COP cluster sample, aiming to assess the stratification properties of the ICM. Methods. We modeled the relations between radius, gas temperature, density, and pressure using a combination of power-laws, also evaluating the intrinsic scatter in these relations. Results. We show that the gas pressure is remarkably well correlated to the density, with very small scatter. Also the temperature correlates with gas density with similar scatter. The slopes of these relations have values that show a clear transition from the inner cluster regions to the outskirts. This transition occurs at the radius rt = 0.19(±0.04) R500 and electron density nt = (1.91 ± 0.21) × 10−3 cm−3 E2(z). We find that above 0.2 R500 the radial thermodynamic profiles are accurately reproduced by a well defined and physically motivated framework, where the dark matter follows the NFW potential and the gas is represented by a polytropic equation of state. By modeling the gas temperature dependence upon both the gas density and radius, we propose a new method to reconstruct the hydrostatic mass profile based only on the relatively inexpensive measurement of the gas density profile.

Diffusion of Innovations: Patenting or Standardization

In this paper, the authors proposed provisions under which the standards are more preferable than patents. They are defined in duopoly model of Standard - Patent. The article shows that the observed criterion (criteria) of efficiency standards in comparison with patents is a small scatter of royalties specific to the assessment of the cost of the license. Based on this criterion, sectors of the economy in which the standard can be more effective than patent for user were identified.

What is a GMC? Are observers and simulators discussing the same star-forming clouds?

Observations and simulations have now reached the point where the giant molecular cloud (GMCs) populations can be studied over a whole galaxy. This is immensely helpful for understanding star formation. Yet, are these two groups really comparing the same objects? While simulators work in 6D (x, y, z, vx, vy, vz) position-position-position (PPP) space, observers see 2 + 1D (RA, Dec, vlos) projected properties along the line of sight, identifying clouds in position-position-velocity (PPV) space. In this research we generated PPP and PPV data for a high-resolution simulated galaxy and compared the identified clouds in both data sets. The results show that 70% of the clouds have a single counterpart in each data structure. Cloud boundaries of these clouds are indeed the same. Scatter of the derived cloud properties (radius and velocity dispersion) between PPP and PPV are typically within a factor of two. However, this small scatter can make it difficult to determine if a cloud is truly gravitationally bound.

Supernovae from yellow, blue supergiants: origin and consequences for stellar evolution

A few core collapse supernovae progenitors have been found to be yellow or blue supergiants. Weshall discuss possible scenarios involving single and close binary evolution allowing to explain this kind of corecollapse supernova progenitors. According to stellar models for both single and close binaries, blue supergiants, at theend of their nuclear lifetimes and thus progenitors of core collapse supernovae, present very different characteristicsfor what concerns their surface compositions, rotational surface velocities and pulsational properties with respect toblue supergiants in their core helium burning phase. We discuss how the small observed scatter of the flux-weightedgravity-luminosity (FWGL) relation of blue supergiants constrains the evolution of massive stars after the Main-Sequence phase and the nature of the progenitors of supernovae in the mass range between 12 and 40 solarmasses. The present day observed surface abundances of blue supergiants, of their pulsational properties, as well asthe small scatter of the FWGL relation provide strong constraints on both internal mixing and mass loss in massivestars and therefore on the end point of their evolution.