A Substantial Population of Low Mass Stars in Luminous Elliptical Galaxies

The stellar initial mass function (IMF) describes the mass distribution of stars at the time of their formation and is of fundamental importance for many areas of astrophysics. The IMF is reasonably well constrained in the disk of the Milky Way but we have very little direct information on the form of the IMF in other galaxies and at earlier cosmic epochs. Here we investigate the stellar mass function in elliptical galaxies by measuring the strength of the Na I doublet and the Wing-Ford molecular FeH band in their spectra. These lines are strong in stars with masses <0.3 Msun and weak or absent in all other types of stars. We unambiguously detect both signatures, consistent with previous studies that were based on data of lower signal-to-noise ratio. The direct detection of the light of low mass stars implies that they are very abundant in elliptical galaxies, making up >80% of the total number of stars and contributing >60% of the total stellar mass. We infer that the IMF in massive star-forming galaxies in the early Universe produced many more low mass stars than the IMF in the Milky Way disk, and was probably slightly steeper than the Salpeter form in the mass range 0.1 - 1 Msun.Comment: To appear in Natur

Influence of mild feed restriction and mild reduction in dietary amino acid content on feeding behaviour of group-housed growing pigs

This study investigates changes in the feeding behaviour of pigs as a result of a restriction in their feed allowance and a reduction in dietary indispensable amino acid (AA) content. Ninety-six Topig Talent × PIC barrows were housed in 8 pens and individually fed either ad libitum (AL) or a restricted diet (RF) from 47 to 145 kg body weight (BW). The amount of feed given to RF pigs was close to their expected voluntary intake, but it was limited to proportions of 0.33, 0.66 and 1.00 of the estimated daily amount of feed in 3 time intervals, 00:01 to 8:00, 8:01 to 16:00 and 16:01 to 24:00 h, respectively. From 86 kg BW, the pigs in 4 of the pens were fed diets with conventional standardized ileal digestible AA content (CAA), while the pigs in the other pens received diets (LAA) in which the proportions of dietary indispensable AA were lowered with respect to CAA by 0.91 from 86 to 118 kg BW and by 0.82 from 118 to 145 kg BW. Automated feeders monitored individual feeding behaviour. Data were analysed by pig and feeding phase with a 2 × 2 factorial design. Over the whole experimental period, feed restriction resulted in a decrease in daily feed intake (7%, P < 0.001), the number of visits (27%, P < 0.001) and the time spent feeding (14%, P < 0.001), but an increase in feed consumption per visit (20%, P = 0.001) and feeding rate (10%, P = 0.032). The reduction in AA increased daily feed intake (7%, P = 0.031), tended to increase feeding rate (14%, P = 0.07) and interacted with feeding regime with respect to the number and duration of feeding visits. During growing and finishing, we observed high, negative, non-linear relationships between feed consumption per visit and visit frequency (R2 = 0.989 to 0.876), between visit duration and visit frequency (R2 = 0.648 to 0.695), and between feeding rate and time spent feeding in a day (R2 = 0.802 to 0.707), and positive linear relationships between visit duration and feed consumption per visit (R2 = 0.614 to 0.570). The individual feeding rate during growing was positively correlated with that during finishing (R2 = 0.458). We conclude that pigs try to adapt their feeding pattern to compensate for a reduction in feed allowance or nutrient restriction by, for example, increasing their feeding rate, which may reflect increased feeding motivation

The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

We describe the design and data sample from the DEEP2 Galaxy Redshift Survey, the densest and largest precision-redshift survey of galaxies at z ~ 1 completed to date. The survey has conducted a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude M_B = -20 at z ~ 1 via ~90 nights of observation on the DEIMOS spectrograph at Keck Observatory. DEEP2 covers an area of 2.8 deg^2 divided into four separate fields, observed to a limiting apparent magnitude of R_AB=24.1. Objects with z < 0.7 are rejected based on BRI photometry in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5 times more efficiently than in a purely magnitude-limited sample. Approximately sixty percent of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets which fail to yield secure redshifts are blue objects that lie beyond z ~ 1.45. The DEIMOS 1200-line/mm grating used for the survey delivers high spectral resolution (R~6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. DEEP2 surpasses other deep precision-redshift surveys at z ~ 1 in terms of galaxy numbers, redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the publicly-available DEEP2 DEIMOS data reduction pipelines. [Abridged]Comment: submitted to ApJS; data products available for download at http://deep.berkeley.edu/DR4

Evaluating assumptions of scales for subjective assessment of thermal environments – Do laypersons perceive them the way, we researchers believe?

International audienc

The ocean sampling day consortium

Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world’s oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits

Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the pi- pi- pi+ final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data show a significant natural parity exchange production of a resonance with spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The resonant nature of this wave is evident from the mass-dependent phase differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2 is deduced.Comment: 7 page, 3 figures; version 2 gives some more details, data unchanged; version 3 updated authors, text shortened, data unchange

Globular cluster systems and galaxy formation

Globular clusters are compact, gravitationally bound systems of up to a million stars. The GCs in the Milky Way contain some of the oldest stars known, and provide important clues to the early formation and continuing evolution of our Galaxy. More generally, GCs are associated with galaxies of all types and masses, from low-mass dwarf galaxies to the most massive early-type galaxies which lie in the centres of massive galaxy clusters. GC systems show several properties which connect tightly with properties of their host galaxies. For example, the total mass of GCs in a system scales linearly with the dark matter halo mass of its host galaxy. Numerical simulations are at the point of being able to resolve globular cluster formation within a cosmological framework. Therefore, GCs link a range of scales, from the physics of star formation in turbulent gas clouds, to the large-scale properties of galaxies and their dark matter. In this Chapter we review some of the basic observational approaches for GC systems, some of their key observational properties, and describe how GCs provide important clues to the formation of their parent galaxies.Comment: 32 pages, 6 figures. Accepted for publication in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-03556

On the nature of the brightest globular cluster in M81

We analyse the photometric, chemical, star formation history and structural properties of the brightest globular cluster (GC) in M81, referred to as GC1 in this work, with the intention of establishing its nature and origin. We find that it is a metal-rich ([Fe/H] = -0.60 +/- 0.10), alpha-enhanced ([alpha/Fe] similar to 0.20 +/- 0.05), core-collapsed (core radius r(c) = 1.2 pc, tidal radius r(t) = 76r(c)), old (&gt; 13 Gyr) cluster. It has an ultraviolet excess equivalent of similar to 2500 blue horizontal branch stars. It is detected in X-rays indicative of the presence of low-mass binaries. With a mass of 1.0 x 10(7) M-circle dot, the cluster is comparable in mass to M31-G1 and is four times more massive than omega Cen. The values of r(c), absolute magnitude and mean surface brightness of GC1 suggest that it could be, like massive GCs in other giant galaxies, the left-over nucleus of a dissolved dwarf galaxy