O. V. Malanushenko

The Hercules-Aquila Cloud

We present evidence for a substantial overdensity of stars in the direction of the constellations of Hercules and Aquila. The cloud is centered at a Galactic longitude of l ≈ 40° and extends above and below the Galactic plane by at least 50°. Given its off-centeredness and height, it is unlikely that the Hercules-Aquila cloud is related to the bulge or thick disk. More likely, this is a new structural component of the Galaxy that passes through the disk. The cloud stretches ~80° in longitude. Its heliocentric distance lies between 10 and 20 kpc so that the extent of the cloud in projection is ~20 kpc by ~15 kpc. It has an absolute magnitude of Mv = -13, and its stellar population appears to be comparable to, but somewhat more metal-rich than, M92.

The clustering of galaxies at z ≈ 0.5 in the SDSS-III data release 9 BOSS-CMASS sample: a test for the ΛCDM cosmology

We present results on the clustering of 282 068 galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS) sample of massive galaxies with redshifts 0.4 < z < 0.7 which is part of the Sloan Digital Sky Survey III project. Our results cover a large range of scales from ∼500 to ∼90 h−1 Mpc. We compare these estimates with the expectations of the flat Λ cold dark matter (ΛCDM) standard cosmological model with parameters compatible with Wilkinson Microwave Anisotropy Probe 7 data. We use the MultiDark cosmological simulation, one of the largest N-body runs presently available, together with a simple halo abundance matching technique, to estimate galaxy correlation functions, power spectra, abundance of subhaloes and galaxy biases. We find that the ΛCDM model gives a reasonable description to the observed correlation functions at z ≈ 0.5, which is remarkably good agreement considering that the model, once matched to the observed abundance of BOSS galaxies, does not have any free parameters. However, we find a ≳10 per cent deviation in the correlation functions for scales ≲ 1 and ∼10–40 h−1 Mpc. A more realistic abundance matching model and better statistics from upcoming observations are needed to clarify the situation. We also estimate that about 12 per cent of the ‘galaxies’ in the abundance-matched sample are satellites inhabiting central haloes with mass M ≳ 1014 h−1 M⊙. Using the MultiDark simulation, we also study the real-space halo bias b of the matched catalogue finding that b = 2.00 ± 0.07 at large scales, consistent with the one obtained using the measured BOSS-projected correlation function. Furthermore, the linear large-scale bias, defined using the extrapolated linear matter power spectrum, depends on the number density n of the abundance-matched sample as b = −0.048 − (0.594 ± 0.02)log10(n/ h3 Mpc−3). Extrapolating these results to baryon acoustic oscillation scales, we measure a scale-dependent damping of the acoustic signal produced by non-linear evolution that leads to ∼2–4 per cent dips at ≳ 3σ level for wavenumbers k ≳ 0.1 h Mpc−1 in the linear large-scale bias.

SDSS IV MaNGA - the spatially resolved transition from star formation to quiescence

FB, RM and KM acknowledge funding from the United Kingdom Science and Technology Facilities Council (STFC). RM acknowledges support from the European Research Council (ERC) Advanced Grant 695671 ‘QUENCH’. AR-L acknowledges partial support from the DIULS regular project PR15143. MB was supported by NSF/AST-1517006. KB was supported by World Premier International Research Centre Initiative (WPI Initiative), MEXT, Japan and by JSPS KAKENHI Grant Number 15K17603. AW acknowledges support from a Leverhulme Early Career Fellowship. AD acknowledges support from The Grainger Foundation.

SDSS-IV MaNGA : environmental dependence of stellar age and metallicity gradients in nearby galaxies

We present a study on the stellar age and metallicity distributions for 1105 galaxies using the STARLIGHT software on MaNGA integral field spectra. We derive age and metallicity gradients by fitting straight lines to the radial profiles, and explore their correlations with total stellar mass M*, NUV-r colour and environments, as identified by both the large scale structure (LSS) type and the local density. We find that the mean age and metallicity gradients are close to zero but slightly negative, which is consistent with the inside-out formation scenario. Within our sample, we find that both the age and metallicity gradients show weak or no correlation with either the LSS type or local density environment. In addition, we also study the environmental dependence of age and metallicity values at the effective radii. The age and metallicity values are highly correlated with M* and NUV-r and are also dependent on LSS type as well as local density. Low-mass galaxies tend to be younger and have lower metallicity in low-density environments while high-mass galaxies are less affected by environment.

Correlation of the He I 1083 nm Line Width and Intensity as a Coronal Hole Identifier

The locations of coronal holes are usually based on equivalent width images in the He I 1083 nm line. However, it is difficult to differentiate coronal holes from the centers of quiet chromospheric network without complementary data and the skill of an experienced observer. Analysis of imaging spectroscopy shows that line width and central intensity are oppositely correlated in coronal holes and quiet Sun. This fact can be used to form images of linear combinations of these quantities in which coronal holes are easily identified.