Calibrated and completeness-corrected optical stellar density maps of the Northern Galactic Plane

© The Author 2016. Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Following on from the second release of calibrated photometry from IPHAS, the INT/WFC Photometric Hα Survey of the Northern Galactic Plane, we present incompleteness-corrected stellar density maps in the r and i photometric bands. These have been computed to a range of limiting magnitudes reaching to 20th magnitude in r and 19th in i (Vega system), and with different angular resolutions – the highest resolution available being 1 arcmin2. The maps obtained cover 94 per cent of the 1800 square degree IPHAS footprint, spanning the Galactic latitude range, −5◦ < b < +5◦, north of the celestial equator. The corrections for incompleteness, due to confusion and sensitivity loss at the faint limit, have been deduced by the method of artificial source injection. The presentation of this method is preceded by a discussion of other more approximate methods of determining completeness. Our method takes full account of position-dependent seeing and source ellipticity in the survey data base. The application of the star counts to testing reddened Galactic disc models is previewed by a comparison with predicted counts along three constant-longitude cuts at 30◦, 90◦ and 175◦: some overprediction of the most heavily reddened 30◦ counts is found, alongside good agreement at 90◦ and 175◦. KeyPeer reviewedFinal Published versio

A 3D extinction map of the northern Galactic plane based on IPHAS photometry

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present a 3D map of extinction in the northern Galactic plane derived using photometry from the INT/WFC Photometric Hα Survey of the northern Galactic plane. The map has fine angular (~10 arcmin) and distance (100 pc) sampling allied to a significant depth (≳5 kpc). We construct the map using a method based on a hierarchical Bayesian model described in a previous article by Sale. In addition to mean extinction, we also measure differential extinction, which arises from the fractal nature of the interstellar medium, and show that it will be the dominant source of uncertainty in estimates of extinction to some arbitrary position. The method applied also furnishes us with photometric estimates of the distance, extinction, effective temperature, surface gravity, and mass for ~38 million stars. Both the extinction map and the catalogue of stellar parameters are made publicly available via http://www.iphas.org/extinction.Peer reviewe

A and F stars as probes of outer Galactic disc kinematics

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 Published by Oxford University Press on behalf of the Royal Astronomical Society.Previous studies of the rotation law in the outer Galactic disc have mainly used gas tracers or clump giants. Here, we explore A and F stars as alternatives: these provide a much denser sampling in the outer disc than gas tracers and have experienced significantly less velocity scattering than older clump giants. This first investigation confirms the suitability of A stars in this role. Our work is based on spectroscopy of ~1300 photometrically selected stars in the red calcium-triplet region, chosen to mitigate against the effects of interstellar extinction. The stars are located in two low Galactic latitude sightlines, at longitudes L = 118°, sampling strong Galactic rotation shear, and L = 178°, near the anticentre. With the use of Markov Chain Monte Carlo parameter fitting, stellar parameters and radial velocities are measured, and distances computed. The obtained trend of radial velocity with distance is inconsistent with existing flat or slowly rising rotation laws from gas tracers (Brand & Blitz 1993; Reid et al. 2014). Instead, our results fit in with those obtained by Huang et al. (2016) from disc clump giants that favoured rising circular speeds. An alternative interpretation in terms of spiral arm perturbation is not straight forward. We assess the role that undetected binaries in the sample and distance error may have in introducing bias, and show that the former is a minor factor. The random errors in our trend of circular velocity are within ±5 kms-1.Peer reviewe

A search for white dwarfs in the Galactic plane: : the field and the open cluster population

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. The Version of Record [R. Raddi, et al, ‘A search for white dwarfs in the Galactic plane: the field and the open cluster population’, Monthly Notices of the Royal Astronomical Society, Vol. 457 (2): 1988-2004, first published online 5 February 2016] is available online at doi: https://doi.org/10.1093/mnras/stw042. © 2016 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We investigated the prospects for systematic searches of white dwarfs at low Galactic latitudes, using the VLT Survey Telescope (VST) H$\alpha$ Photometric Survey of the Galactic plane and Bulge (VPHAS+). We targeted 17 white dwarf candidates along sightlines of known open clusters, aiming to identify potential cluster members. We confirmed all the 17 white dwarf candidates from blue/optical spectroscopy, and we suggest five of them to be likely cluster members. We estimated progenitor ages and masses for the candidate cluster members, and compared our findings to those for other cluster white dwarfs. A white dwarf in NGC 3532 is the most massive known cluster member (1.13 M$_{\odot}$), likely with an oxygen-neon core, for which we estimate an $8.8_{-4.3}^{+1.2}$ M$_{\odot}$ progenitor, close to the mass-divide between white dwarf and neutron star progenitors. A cluster member in Ruprecht 131 is a magnetic white dwarf, whose progenitor mass exceeded 2-3 M$_{\odot}$. We stress that wider searches, and improved cluster distances and ages derived from data of the ESA Gaia mission, will advance the understanding of the mass-loss processes for low- to intermediate-mass stars.Peer reviewedFinal Published versio

A small-N cross-sectional study of British unions' environmental attitudes and activism - and the prospect of a green-led renewal

Unions understand the environmental agenda as a technocentric one but also believe it can function as a vehicle for renewal. It is developing slowly, with unions behaving cautiously—resources are scarce. Although popular with members, there is limited evidence that it is effective as a recruitment tool and whilst employers are willing to work in partnership with unions on it, this may confer only phony insider status. Overall, the agenda has limited appeal to the types of employees and employers unions must recruit in order to grow. Identifying a clear environmental premium for members may help

The deep OB-star population in Carina from the VST Photometric H-alpha Survey (VPHAS+)

© The Authors 2016. Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Massive OB stars are critical to the ecology of galaxies and yet our knowledge of OB stars in the Milky Way, fainter than V ∼ 12, remains patchy. Data from the VST Photometric Hα Survey (VPHAS+) permit the construction of the first deep catalogues of blue excess-selected OB stars, without neglecting the stellar field. A total of 14 900 candidates with 2MASS cross-matches are blue-selected from a 42 deg2 region in the Galactic plane, capturing the Carina Arm over the Galactic longitude range 282◦ 293◦. Spectral energy distribution fitting is performed on these candidates’ combined VPHAS+ u, g, r, i and 2MASS J, H, K magnitudes. This delivers effective temperature constraints, statistically separating O from early-B stars and high-quality extinction parameters, A0 and RV (random errors typically ∼0.1). The high-confidence O-B2 candidates number 5915 and a further 5170 fit to later B spectral type. Spectroscopy of 276 of the former confirms 97 per cent of them. The fraction of emission-line stars among all candidate B stars is 7–8 per cent. Greyer (RV > 3.5) extinction laws are ubiquitous in the region, over the distance range 2.5–3 to ∼10 kpc. Near prominent massive clusters, RV tends to rise, with particularly large and chaotic excursions to RV ∼ 5 seen in the Carina Nebula. The data reveal a hitherto unnoticed association of 108 O-B2 stars around the O5If+ star LSS 2063 ( = 289.◦77, b = −1.◦22). Treating the OB star scaleheight as a constant within the thin disc, we find an orderly mean relation between extinction (A0) and distance in the Galactic longitude range, 287.◦6 << 293. ◦5, and infer the subtle onset of thin-disc warping. A halo around NGC 3603, roughly a degree in diameter, of ∼500 O-B2 stars with 4 < A0(mag) < 7 is noted.Peer reviewe

INITIAL DATA RELEASE OF THEKEPLER-INT SURVEY

This paper describes the first data release of the Kepler-INT Survey (KIS), that covers a 116 deg2 region of the Cygnus and Lyra constellations. The Kepler field is the target of the most intensive search for transiting planets to date. Despite the fact that the Kepler mission provides superior time series photometry, with an enormous impact on all areas of stellar variability, its field lacks optical photometry complete to the confusion limit of the Kepler instrument necessary for selecting various classes of targets. For this reason, we follow the observing strategy and data reduction method used in the IPHAS and UVEX galactic plane surveys in order to produce a deep optical survey of the Kepler field. This initial release concerns data taken between May and August 2011, using the Isaac Newton Telescope on the island of La Palma. Four broadband filters were used, U, g, r, i, as well as one narrowband one, Halpha, reaching down to a 10-sigma limit of around 20th mag in the Vega system. Observations covering around 50 deg2, thus about half of the field, passed our quality control thresholds and constitute this first data release. We derive a global photometric calibration by placing the KIS magnitudes as close as possible to the Kepler Input Catalog (KIC) photometry. The initial data release catalogue containing around 6 million sources from all the good photometric fields is available for download from the KIS webpage, as well as via MAST.Comment: 10 pages, 7 figures - Accepted for publication in the Astronomical Journa

Initial data release of the Kepler-INT survey

This paper describes the first data release of the Kepler-INT Survey (KIS), that covers a 116 deg2 region of the Cygnus and Lyra constellations. The Kepler field is the target of the most intensive search for transiting planets to date. Despite the fact that the Kepler mission provides superior time series photometry, with an enormous impact on all areas of stellar variability, its field lacks optical photometry complete to the confusion limit of the Kepler instrument necessary for selecting various classes of targets. For this reason, we follow the observing strategy and data reduction method used in the IPHAS and UVEX galactic plane surveys in order to produce a deep optical survey of the Kepler field. This initial release concerns data taken between May and August 2011, using the Isaac Newton Telescope on the island of La Palma. Four broadband filters were used, U, g, r, i, as well as one narrowband one, Halpha, reaching down to a 10-sigma limit of around 20th mag in the Vega system. Observations covering around 50 deg2, thus about half of the field, passed our quality control thresholds and constitute this first data release. We derive a global photometric calibration by placing the KIS magnitudes as close as possible to the Kepler Input Catalog (KIC) photometry. The initial data release catalogue containing around 6 million sources from all the good photometric fields is available for download from the KIS webpage, as well as via MAST