Monday, October 19, 2020

Domesticated South Asian Cows Arrived In The Near East, En Masse, In The Bronze Age

Razib Khan, at the Brown Pundits group blog, calls attention to a July 2019 paper in Science demonstrating with ancient cattle mtDNA that there was surge of South Asian domesticated cattle from the Indus River Valley civilization into the Near East in the Bronze Age ca. 4000 to 3500 years ago. Before that time period only European cattle were present in the Near East. 

This was probably in response to the civilization crushing drought that his both regions simultaneously around 2200 BCE to 2000 BCE, and ultimately led to the collapse of the Akkadian Empire in the Near East, to the collapse of an Egyptian dynasty, and to the collapse of the Harappan civilization in the Indus River Valley (including the demise of a river system at the heart of the Rig Vedic epics). This climate event was also probably a pivotal trigger for Indo-European expansion, creating a vacuum of collapsed civilizations into which a culture from the steppe which was better adapted to these conditions could and did expand.

This paper shows South Asian-Near East contracts that pervasively influenced daily life in the Near East despite the fact that Indo-European subculture, the Indo-Aryans (i.e. the Sanskrit speaking population that became dominant in much of South Asia in the Bronze Age, and had an even broader and  ore lasting religious impact), left only a short term cultural and linguistic impact in the Near East, and didn't leave much of a demic (i.e. population genetic) impact in the Near East either.

The interesting aspect of cattle is that there are really two species that intermix. Using mtDNA researchers estimate indicus and taurus diverged 300,000 to 2,000,000 years ago. . . . Ancient cattle from the Near East are all taurus. . . . [But] there is a massive jump in genome-wide indicus ancestry across the Near East between 2000 and 1500 BC. As the authors note this can’t be diffusion; the jump is too sudden and sweeping.

So what happened during this period? As noted in the paper: Bronze Age civilization almost collapsed around ~2000 BC. More concretely, after 2000 BC is when we see evidence of Indo-Europeans in the Near East. The Indo-Aryan Mittani show up in Mesopotamia in ~1600 BC. The Indo-European Hittites, the Nesa, are known from Anatolia a bit earlier. This is also the period that small, but detectable, levels of “steppe” ancestry show up in some ancient samples.

Before this paper, I would have leaned to the position that the Mittani Indo-Aryans migrated directly from the Sintashta homeland without much contact with Indian Indo-Aryans. 
These data are too suggestive of a widespread zone of expanding agro-pastoralists that existed between western South Asia and the Near East between 2000 BC and 1500 BC. . . . Aside from the Mittani the evidence of Indo-Aryans in the Near East is tenuous, though some of the Kassites of Babylonia may have had Indo-European affinities. There is not nearly as strong a genetic imprint of steppe in the Fertile Crescent as in Northwest India. 
The Hittites were very different from Indo-Aryans, who seem to have the closest relationship to the Slavic language family.

The indicus breed is adapted to tropical dry climates. It seems plausible that the Indo-Aryan[s] . . . facilitated the spread of this breed in the centuries before 1500 BC.

Quote of the Day

Genzel and Ghez led two teams that peered into the center of our galaxy. By carefully measuring the way stars moved deep in the core, they figured out something we now teach children: that our beloved Milky Way has a dark and chewy center, an enormous black hole around which everything else revolves.

From 4gravitons writing about two of the Nobel Prize in Physics award winners in 2020.

Annual Variation In Polonium Decay Rates?

Polonium is atomic element 84 which is a radioactive metal with no stable isotopes and several unstable ones (i.e. isotopes are variations of a chemical element with the same number of protons but different numbers of neutrons). One of those isotopes (Po-210) is the penultimate daughter of natural uranium-238 and was discovered in 1898 by Marie and Pierre Curie. But its short half-life of 138 days means that it is almost completely absent in nature. Polonium is usually produced in milligram quantities by the neutron irradiation of bismuth.

More or less by hypothesis, the radioactive decay of elements is an internal process which is indifferent to the environment. 

But a study at the underground low-background conditions of the Baksan Neutrino Observatory has detected annual and other kinds of periodic variation in the half-lives of three different Polonium isotopes, specifically, annular, solar-daily, lunar-daily and sidereal-daily variations, which would suggest that some sort of cosmic ray bombardment from the Sun, mitigated by shielding from the Earth and Moon, influences the decay rates of these radioactive isotopes. 

The effect sizes are modest, but statistically significant (more than two but less the four sigma), with a period consistent with one year (that could have a physical reality) in each case, but significantly varying phases that could relate, for example, to geometric Moon-Earth configurations relative to the Sun.

As the conclusion to the paper explains (the last highlighted sentence is clearly an error that includes the words "do not" where it clearly means the opposite of what it says):
Conclusion that half-life values of the 214Po, 213Po and 212Po isotopes are feel annular variations with similar amplitudes could be done on a base of a comparison of graphs on the Fig. 1. It is shown that two independent sequential sets of the 214Po τ -values (τ ≡ T1/2 ) obtained in the spaced laboratories can be described by sinusoidal functions. 
A sine function approximates a set of the 214Po τ -values with a time duration of ∼ 973 days obtained at the BNO has an amplitude A = (5.0 ± 1.5) · 10^−4 , a period ω = (365 ± 8) days and a phase ϕ = (170 ± 7) days relative to the 1st January, 2012 year. The function approximates a set of τ -values with a time duration of 1460 days obtained at the KhNU has an amplitude A = (4.9±1.8)·10^−4 , a period ω = (377±13) days and a phase φ = (77±10) days. 
The 213Po τ -value set with a time duration of ∼ 1700 days can be described by a sinusoidal function with an amplitude A = (3.9 ± 1.2) · 10^−4 , a period ω = (370±13) days and a phase φ = (130±9) days. 
The 212 Po τ -value set with a time duration of ∼ 670 days can be described by a sinusoidal function with an amplitude A = (7.5±1.6)·10^−4 , a period ω = (375 ± 13) days and a phase φ = (40 ± 10) days. 
Observed differences of the phases of the approximated sine functions have not any unambiguous explanations and define necessity of further investigations. These differences are complicate a search of the common factors caused the viewed variations. None of environmental factors examined up to now (pressure, air humidity and temperature, layer of air ionization, earth magnetic field variations, set-up instability) do not show correlations with the observed 214Po, 213Po and 212Po half-life values variations. Investigations are continuing.

The Ethics of Lunar And Mar Exploration

I predict that planners of new missions of the Moon and Mars will completely ignore the anti-colonial ethical analysis of this paper.

Ethical Exploration and the Role of Planetary Protection in Disrupting Colonial Practices

We recommend that the planetary science and space exploration community engage in a robust reevaluation concerning the ethics of how future crewed and uncrewed missions to the Moon and Mars will interact with those planetary environments. This should occur through a process of community input, with emphasis on how such missions can resist colonial structures. Such discussions must be rooted in the historical context of the violent colonialism in the Americas and across the globe that has accompanied exploration of Earth. The structures created by settler colonialism are very much alive today, impact the scientific community, and are currently replicated in the space exploration communities' plans for human exploration and in-situ resource utilization. 
These discussions must lead to enforceable planetary protection policies that create a framework for ethical exploration of other worlds. 
Current policy does not adequately address questions related to in-situ resource utilization and environmental preservation and is without enforcement mechanisms. Further, interactions with potential extraterrestrial life have scientific and moral stakes. Decisions on these topics will be made in the coming decade as the Artemis program enables frequent missions to the Moon and crewed missions to Mars. Those first choices will have irreversible consequences for the future of human space exploration and must be extremely well considered, with input from those beyond the scientific community, including expertise from the humanities and members of the general public. Without planetary protection policy that actively resists colonial practices, they will be replicated in our interactions and exploration of other planetary bodies. The time is now to engage in these difficult conversations and disrupt colonial practices within our field so that they are not carried to other worlds.
Comments:A submission to the Planetary Science and Astrobiology Decadal Survey 2023-2032
Subjects:Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:arXiv:2010.08344 [astro-ph.IM]

Leading Simulations Mischaracterize Star Formation

Some of the leading simulations of the star formation process in galaxies don't reflect the mix of star forming galaxies and galaxies that are passive and not forming many new stars that is observed, while some of the less popular simulations do. This suggests that the errant simulations are missing some important principle.

The specific star formation rate function at different mass scales and quenching: A comparison between cosmological models and SDSS

We present the eddington bias corrected Specific Star Formation Rate Function (sSFRF) at different stellar mass scales from a sub-sample of the Sloan Digital Sky Survey Data Release DR7 (SDSS), which is considered complete both in terms of stellar mass (M) and star formation rate (SFR). The above enable us to study qualitatively and quantitatively quenching, the distribution of passive/star-forming galaxies and perform comparisons with the predictions from state-of-the-art cosmological models, within the same M and SFR limits. We find that at the low mass end (M=109.51010M) the sSFRF is mostly dominated by star-forming objects. However, moving to the two more massive bins (M=10101010.5M and M=1010.51011M) a bi-modality with two peaks emerges. One peak represents the star-forming population, while the other describes a rising passive population. The bi-modal form of the sSFRFs is not reproduced by a range of cosmological simulations (e.g. Illustris, EAGLE, Mufasa, IllustrisTNG) which instead generate mostly the star-forming population, while a bi-modality emerges in others (e.g. L-Galaxies, Shark, Simba). Our findings reflect the need for the employed quenching schemes in state-of-the-art models to be reconsidered, involving prescriptions that allow "quenched galaxies" to retain a small level of SF activity (sSFR = 1011yr1-1012yr1) and generate an adequate passive population/bi-modality even at intermediate masses (M=10101010.5M).
Comments:13 pages, 4 Figures, Accepted to MNRAS
Subjects:Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as:arXiv:2010.08173 [astro-ph.GA]

A More Fundamental Measure Of Galaxy Size

An October 15, 2020 pre-print comes up with a theoretically rather than observationally motivated way to measure the size of a galaxy that reduces the scatter in certain measurements from ± 15% at one standard deviation (0.06 dex) from ± 45% at one standard deviation (0.18 dex). 

This suggests that the some of the scatter in the "radial acceleration relation" is due to an imperfect definition of radius and tends to make the relation even tighter.

As used in the abstract of that paper, a dex is an order of magnitude (i.e. factor of 10), So 10dex equals the scatter in terms of a ratio value, which times 100 equal a percentage variation.

A dex is completely equivalent to a “bel” or “decade” which occasionally come up in engineering and physics. The bel is much more widely known with its deci- prefix as the “decibel.” A decibel is therefore equal to 0.1 dex.

Using the dex terminology is one way to make big margins of error (which are common in astronomy) look smaller, and also is helpful when you are discussing power law functions where logarithmic error relationships make more sense that quoting scatter in absolute terms that don't adjust the upper limit and lower limit relative to each other for scale.  

A historical perspective on the concept of galaxy size

A brief narrative on how the effective radius and isophotal diameters were accepted as galaxy size measures is presented. Evidence suggests that these parameters were defined only based on observational premises, independent of any astrophysical theories. An alternative, new physically motivated size definition based on the expected gas density threshold required for star formation in galaxies is discussed. The intrinsic scatter of the size-stellar mass relation using the new size measure is 0.06 dex, three times smaller than that of the relation with the effective radius as size. The new physically motivated size measure can be adopted in upcoming deep, wide imaging surveys.
Comments:A concise version of this article was published in the RNAAS 'Focus on AAS 236'
Subjects:Astrophysics of Galaxies (astro-ph.GA)
Journal reference:RNAAS, Volume 4, Issue 7, id.117 (2020)
Cite as:arXiv:2010.07946 [astro-ph.GA]