Evidence for Low Black Hole Spin and Physically Motivated Accretion Models from Millimeter VLBI Observations of Sagittarius A*

Millimeter very-long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, this provides access to the region in the immediate vicinity of the horizon. Broderick et al. (2009) have already shown that by leveraging spectral and polarization information as well as accretion theory, it is possible to extract accretion-model parameters (including black hole spin) from mm-VLBI experiments containing only a handful of telescopes. Here we repeat this analysis with the most recent mm-VLBI data, considering a class of aligned, radiatively inefficient accretion flow (RIAF) models. We find that the combined data set rules out symmetric models for Sgr A*'s flux distribution at the 3.9-sigma level, strongly favoring length-to-width ratios of roughly 2.4:1. More importantly, we find that physically motivated accretion flow models provide a significantly better fit to the mm-VLBI observations than phenomenological models, at the 2.9-sigma level. This implies that not only is mm-VLBI presently capable of distinguishing between potential physical models for Sgr A*'s emission, but further that it is sensitive to the strong gravitational lensing associated with the propagation of photons near the black hole. Based upon this analysis we find that the most probable magnitude, viewing angle, and position angle for the black hole spin are a=0.0(+0.64+0.86), theta=68(+5+9)(-20-28) degrees, and xi=-52(+17+33)(-15-24) east of north, where the errors quoted are the 1-sigma and 2-sigma uncertainties.Comment: 15 pages, 10 figures, submitted to Ap

The influence of infant irritability on maternal sensitivity in a sample of very premature infants

The relationship between maternal sensitivity and infant irritability was investigated in a short-term longitudinal study of 29 very preterm infants. Infant irritability was assessed at term with the Brazelton NBAS, the Mother and Baby Scales (MABS) and the Crying Pattern Questionnaire (CPQ). Maternal sensitivity was assessed by nurses' ratings in the neonatal care unit and at three months during motherinfant interaction observation. Cross-lagged panel analysis indicated that neonatal irritability did not influence sensitivity at 3 months nor did maternal sensitivity in the newborn period lead to reduced irritability at 3 months. Both irritability and maternal sensitivity showed moderate stability over time (r=.55 and r=.60, respectively). It is concluded that in early infancy maternal sensitivity shows little influence on infant irritability in very preterm infants

Strikingly higher frequency in centenarians and twins of mtDNA mutation causing remodeling of replication origin in leukocytes

The presence of a genetic component in longevity is well known. Here, the association of a mtDNA mutation with a prolonged life span in humans was investigated. Large-scale screening of the mtDNA main control region in leukocytes from subjects of an Italian population revealed a homoplasmic C150T transition near an origin of heavy mtDNA-strand synthesis in approximate to 17% of 52 subjects 99-106 years old, but, in contrast, in only 3.4% of 117 younger individuals (P = 0.0035). Evidence was obtained for the contribution of somatic events, under probable nuclear genetic control, to the striking selective accumulation of the mutation in centenarians. In another study, among leukocyte mtDNA samples from 20 monozygotic and 18 dizygotic twins, 60-75 years old, 30% (P = 0.0007) and 22% (P = 0.011), respectively, of the individuals involved exhibited the homoplasmic C150T mutation. In a different system, i.e., in five human fibroblast longitudinal studies, convincing evidence for the aging-related somatic expansion of the C150T mutation, up to homoplasmy, was obtained. Most significantly, 5' end analysis of nascent heavy mtDNA strands consistently revealed a new replication origin at position 149, substituting for that at 151, only in C150T mutation carrying samples of fibroblasts or immortalized lymphocytes. Considering the aging-related health risks that the centenarians have survived and the developmental risks of twin gestations, it is proposed that selection for a remodeled replication origin, inherited or somatically acquired, provides a survival advantage and underlies the observed high incidence of the C150T mutation in centenarians and twins

The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations

Recent high resolution observations of the Galactic center black hole allow for direct comparison with accretion disk simulations. We compare two-temperature synchrotron emission models from three dimensional, general relativistic magnetohydrodynamic simulations to millimeter observations of Sgr A*. Fits to very long baseline interferometry and spectral index measurements disfavor the monochromatic face-on black hole shadow models from our previous work. Inclination angles \le 20 degrees are ruled out to 3 \sigma. We estimate the inclination and position angles of the black hole, as well as the electron temperature of the accretion flow and the accretion rate, to be i=50+35-15 degrees, \xi=-23+97-22 degrees, T_e=(5.4 +/- 3.0)x10^10 K and Mdot=(5+15-2)x10^-9 M_sun / yr respectively, with 90% confidence. The black hole shadow is unobscured in all best fit models, and may be detected by observations on baselines between Chile and California, Arizona or Mexico at 1.3mm or .87mm either through direct sampling of the visibility amplitude or using closure phase information. Millimeter flaring behavior consistent with the observations is present in all viable models, and is caused by magnetic turbulence in the inner radii of the accretion flow. The variability at optically thin frequencies is strongly correlated with that in the accretion rate. The simulations provide a universal picture of the 1.3mm emission region as a small region near the midplane in the inner radii of the accretion flow, which is roughly isothermal and has \nu/\nu_c ~ 1-20, where \nu_c is the critical frequency for thermal synchrotron emission.Comment: 14 pages, 17 figures, accepted by Ap

Biomimetic bluff body drag reduction by self-adaptive porous flaps

The performances of an original passive control system based on a biomimetic approach are assessed by investigating the flow over a bluff-body. This control device consists in a couple of flaps made from the combination of a rigid plastic skeleton coated with a porous fabric mimicking the shaft and the vane of the bird's feathers, respectively. The sides of a square cylinder have been fitted with this system so as to enable the flaps to freely rotate around their leading edge. This feature allows the movable flaps to self-adapt to the flow conditions. Comparing both the uncontrolled and the controlled flow, a significant drag reduction (up to 22%) has been obtained over a broad range of Reynolds number. The investigation of the mean flow reveals a noticeable modification of the flow topology at large scale in the vicinity of the controlled cylinder accounting for the increase of the pressure base in comparison with the natural flow. Meanwhile, the study of the relative motion of both flaps points out that their dynamics is sensitive to the Reynolds number. Furthermore, the comparative study of the flow dynamics at large scale suggest a lock-in coupling of the flap motion and the vortex shedding.Comment: 19 pages, 17 figures, submitted to Comptes-Rendus de l' Acad\'emie des Sciences (M\'ecanique

Incremental events in the construction of sambaquis, southeastern Santa Catarina.

Moundbuilding is a cross-cultural phenomenon of nearly world-wide scope. In this article some of the moundbuilding processes related to the sambaquis (shellmounds) from the coast of Santa Catarina State, Brasil, are examined, focusing on field research at the sambaqui Jaboticabeira II. By means of analysing the mounding up processes at that site, attention is drawn to its social and demographic corollaries, which speak of considerable social elaboration and territorial permanence in time.A construção de cômoros artificiais (mounds) é um fenômeno de amplo alcance em termos globais. Neste artigo são examinados alguns dos processos responsáveis pela construção destas estruturas no litoral sul de Santa Catarina, tomando-se como referência os trabalhos realizados no sambaqui Jaboticabeira II, município de Jaguaruna. Além da análise dos processos envolvidos na construção daquele sambaqui, procura-se chamar a atenção para os aspectos sociais e demográficos destes mesmos processos, evidenciando um sistema regional de considerável complexidade social e duração cronológica

A VLA Study of Ultracompact and Hypercompact H II Regions from 0.7 to 3.6 cm

We report multi-frequency Very Large Array observations of three massive star formation regions (MSFRs) containing radio continuum components that were identified as broad radio recombination line (RRL) sources and hypercompact (HC) H II region candidates in our previous H92alpha and H76alpha study: G10.96+0.01 (component W), G28.20-0.04 (N), and G34.26+0.15 (B). An additional HC H II region candidate, G45.07+0.13, known to have broad H66alpha and H76alpha lines, small size, high electron density and emission measure, was also included. We observed with high spatial resolution (0.9" to 2.3") the H53alpha, H66alpha, H76alpha, and H92alpha RRLs and the radio continuum at the corresponding wavelengths (0.7 to 3.6 cm). The motivation for these observations was to obtain RRLs over a range of principal quantum states to look for signatures of pressure broadening and macroscopic velocity structure. We find that pressure broadening contributes significantly to the line widths, but it is not the sole cause of the broad lines. We compare radio continuum and dust emission distributions and find a good correspondence. We also discuss maser emission and multi-wavelength observations reported in the literature for these MSFRs.Comment: Accepted for publication in ApJ; 55 pages, 10 tables, 12 figure