Molecular Hydrogen emission from disks in the eta Chamaeleontis cluster

Disks in the 6 Myr old cluster eta Chamaeleontis were searched for emission from hot H2. Around the M3 star ECHAJ0843.3-7905 we detect circumstellar gas orbiting at ~2 AU. If the gas is UV-excited, the ro-vibrational line traces a hot gas layer supported by a disk of mass ~0.03Msolar, similar to the minimum mass solar nebula. Such a gas reservoir at 6 Myr would promote the formation and inwards migration of gas giant planets.Comment: Accepted for publication in MNRAS. 9 page

Infrared array spectroscopy with cooled grating spectrometer 4

The work contained in this thesis is concerned with the design and construction of a near-infrared spectrometer for astronomical applications, Cooled Grating Spectrometer 4 (CGS4). The results of two observational projects carried out with the instrument on the United Kingdom Infrared Telescope are presented.CGS4 is one of the first infrared spectrometers to incorporate a 2D detector array, and the design of the spectrometer is driven by the desire to maximise the improve­ments in sensitivity which can be obtained with such an array. The need for high throughput and good image quality is discussed, and the way in which they have been achieved outlined. Other factors which affect the sensitivity of the instrument are the sky-background emission, thermal background from the instrument and telescope and detector noise. The method by which each of these is minimised is outlined. CGS4 was designed as an instrument which could be applied to the disparate projects which benefit from observations in the NIR waveband range. These include observations of molecules in star-forming regions, studies of emission lines from active galactic nuclei, and studies of gas dynamics.Two aspects of optimising observations in the NIR are discussed in detail. For ob­servations in the 1- 2.3/im region, emission from hydroxyl in the Earth’s atmosphere dominates the sky background. The intensity of the line emission from OH varies by ~10% on timescales of ~10mins. As a result, on-source exposure times should be re­stricted to 60s, setting a fundamental limit to the sensitivity achievable for observations of extended sources. Flat-fielding a 2D array spectrometer, to calibrate the relative gains of the pixels, is another area which is explored in this work. The reasons for excluding the methods used for optical astronomy and NIR imaging are discussed. The solution for CGS4 was to provide with a tailor-made “calibration unit” . The design of this unit and the resulting success in flat-fielding observations is detailed.The astronomical results reported concern observations of emission from the hydrogen molecule. There are two predominant methods of exciting H2 : radiative excitation by UV photons with energies less than 13.6eV or collisional excitation in shocks. Excited H2 decays by transitions in the rotational-vibrational bands of the ground electronic state, emitting NIR photons. The emission spectrum, specifically the 1-0 S (l)/2-l S(l) line ratio, is frequently used to diagnose the excitation mechanism. Recent models of the emission from H2 have shown that for gas densities above a critical density, the emission from radiatively excited gas can emulate that from a collisionally excited gas, and that radiative excitation of H2 may be more widespread than previously thought.The planetary nebula, Hubble 12, was identified by Dinerstein et al. (1987) as asource of fluorescent emission from H2 . A spectrum taken with CGS4 confirms this result, in the light of the recent models, through observations of the emission from higher rotational-vibrational levels not previously detected in this source. The emission is shown to arise from a gas of density 104-105cm-3 illuminated by a source of UV fieldstrength 104 times that of the interstellar medium.H2 emission from a ring of molecular material which surrounds the Galactic centre was identified as being shock excited when first measured by Gatley et al. (1984). Conditions at the Galactic centre, and the evidence for recent star—formation, have prompted a re-measurement of the H2 spectrum from this source. It is shown that, indeed, radiative excitation of a dense (~ 10(6)cm(- 3)) gas by a UV field of 10(5)G(o) is sufficient to explain the H2 observations. The dynamics of the gas has also been investigated. The observations confirm that the ring has a radius of 1.54pc, at which point the velocity of the gas is 100km s-1 , and that the velocity has a keplerian dependence on radius. This is consistent with the gas orbiting in the gravitational field of a compact, central source of 4xl0(6) M0

A randomised controlled trial of pelvic floor muscle training for stages I and II pelvic organ prolapse

Abstract Forty-seven women participated in a pilot study for a multi-centre randomized controlled trial of the effectiveness of pelvic floor muscle training (PFMT) for women with prolapse. Women with symptomatic stage I or II prolapse [measured by Pelvic Organ Prolapse Quantification (POP-Q)] were randomized to a 16-week physiotherapy intervention (PFMT and lifestyle advice; n=23) or a control group receiving a lifestyle advice sheet (n=24). Symptom severity and quality of life were measured via postal questionnaires. Blinded POP-Q was performed at baseline and follow-up. Intervention women had significantly greater improvement than controls in prolapse symptoms (mean score decrease 3.5 versus 0.1, p=0.021), were significantly more likely to have an improved prolapse stage (45% versus 0%, p=0.038) and were significantly more likely to say their prolapse was better (63% versus 24%, p=0.012). The data support the feasibility of a substantive trial of PFMT for prolapse. A multi-centre trial is underway.This study was funded by the Chief Scientist Office, Scottish Government (CZH/4/95)

Randomised controlled feasibility trial of an evidence-informed behavioural intervention for obese adults with additional risk factors

Peer reviewedPublisher PD

Illuminating evaporating protostellar outflows: ERIS/SPIFFIER reveals the dissociation and ionization of HH 900

Protostellar jets and outflows are signposts of active star formation. In H II regions, molecular tracers like CO only reveal embedded portions of the outflow. Outside the natal cloud, outflows are dissociated, ionized, and eventually completely ablated, leaving behind only the high-density jet core. Before this process is complete, there should be a phase where the outflow is partially molecular and partially ionized. In this paper, we capture the HH 900 outflow while this process is in action. New observations from the ERIS/SPIFFIER near-IR integral field unit (IFU) spectrograph using the K-middle filter ($\lambda$=2.06-2.34 $\mu$m) reveal H$_2$ emission from the dissociating outflow and Br-$\gamma$ tracing its ionized skin. Both lines trace the wide-angle outflow morphology but H$_2$ only extends $\sim$5000 au into the H II region while Br-$\gamma$ extends the full length of the outflow ($\sim$12,650 au), indicating rapid dissociation of the molecules. H$_2$ has higher velocities further from the driving source, consistent with a jet-driven outflow. Diagnostic line ratios indicate that photoexcitation, not just shocks, contributes to the excitation in the outflow. We argue that HH 900 is the first clear example of an evaporating molecular outflow and predict that a large column of neutral material that may be detectable with ALMA accompanies the dissociating molecules. Results from this study will help guide the interpretation of near-IR images of externally irradiated jets and outflows such as those obtained with the James Webb Space Telescope (JWST) in high-mass star-forming regions where these conditions may be common.Comment: MNRAS, accepte

Illuminating evaporating protostellar outflows: ERIS/SPIFFIER reveals the dissociation and ionization of HH 900

Protostellar jets and outflows are signposts of active star formation. In H II regions, molecular tracers like CO only reveal embedded portions of the outflow. Outside the natal cloud, outflows are dissociated, ionized, and eventually completely ablated, leaving behind only the high-density jet core. Before this process is complete, there should be a phase where the outflow is partially molecular and partially ionized. In this paper, we capture the HH 900 outflow while this process is in action. New observations from the Enhanced Resolution Imager and Spectrograph/SPIFFIER near-infrared (IR) integral field unit spectrograph using the K-middle filter (λ = 2.06–2.34 μm) reveal H2 emission from the dissociating outflow and Br-γ tracing its ionized skin. Both lines trace the wide-angle outflow morphology but H2 only extends ∼5000 au into the H II region while Br-γ extends the full length of the outflow (∼12 650 au), indicating rapid dissociation of the molecules. H2 has higher velocities further from the driving source, consistent with a jet-driven outflow. Diagnostic line ratios indicate that photoexcitation, not just shocks, contributes to the excitation in the outflow. We argue that HH 900 is the first clear example of an evaporating molecular outflow and predict that a large column of neutral material that may be detectable with Atacama Large Millimeter Array accompanies the dissociating molecules. Results from this study will help guide the interpretation of near-IR images of externally irradiated jets and outflows such as those obtained with the JWST in high-mass star-forming regions where these conditions may be common

Daytime site characterisation of La Palma, and its relation to night-time conditions

This paper presents preliminary daytime profiles taken using a Wide-Field Shack-Hartmann Sensor at the Swedish Solar Telescope (SST), La Palma. These are contrasted against Stereo-SCIDAR data from corresponding nights to assess the validity of the assumptions currently used for simulating the performances of possible Multi-Conjugate Adaptive Optics (MCAO) systems for future solar telescopes, especially the assumption that the structure of the high altitude turbulence is mostly similar between the day and the night. We find that for our data both the altitude and the strength of the turbulence differ between the day and the night, although more data is required to draw any conclusions about typical behaviour and conditions

Investigating the Impact of Metallicity on Star Formation in the Outer Galaxy. I. VLT/KMOS Survey of Young Stellar Objects in Canis Major

The effects of metallicity on the evolution of protoplanetary disks may be studied in the outer Galaxy where the metallicity is lower than in the solar neighbourhood. We present the VLT/KMOS integral field spectroscopy in the near-infrared of $\sim$120 candidate young stellar objects (YSOs) in the CMa-$\ell$224 star-forming region located at a Galactocentric distance of 9.1 kpc. We characterise the YSO accretion luminosities and accretion rates using the hydrogen Br$\gamma$ emission and find the median accretion luminosity of $\log{(L_{\rm acc})} = -0.82^{+0.80}_{-0.82} L_\odot$. Based on the measured accretion luminosities, we investigate the hypothesis of star formation history in the CMa-$\ell$224. Their median values suggest that Cluster C, where most of YSO candidates have been identified, might be the most evolved part of the region. The accretion luminosities are similar to those observed toward low-mass YSOs in the Perseus and Orion molecular clouds, and do not reveal the impact of lower metallicity. Similar studies in other outer Galaxy clouds covering a wide range of metallicities are critical to gain a complete picture of star formation in the Galaxy.Comment: Accepted for publication in APJS, 51 pages, 37 figures, 6 table

Two More Candidate AM Canum Venaticorum (AM CVn) Binaries from the Sloan Digital Sky Survey

AM CVn systems are a select group of ultracompact binaries with the shortest orbital periods of any known binary subclass; mass-transfer is likely from a low-mass (partially-)degenerate secondary onto a white dwarf primary, driven by gravitational radiation. In the past few years, the Sloan Digital Sky Survey (SDSS) has provided five new AM CVns. Here we report on two further candidates selected from more recent SDSS data. SDSS J1208+3550 is similar to the earlier SDSS discoveries, recognized as an AM CVn via its distinctive spectrum which is dominated by helium emission. From the expanded SDSS Data Release 6 (DR6) spectroscopic area, we provide an updated surface density estimate for such AM CVns of order 10^{-3.1} to 10^{-2.5} per deg^2 for 15<g<20.5. In addition, we present another new candidate AM CVn, SDSS J2047+0008, that was discovered in the course of followup of SDSS-II supernova candidates. It shows nova-like outbursts in multi-epoch imaging data; in contrast to the other SDSS AM CVn discoveries, its (outburst) spectrum is dominated by helium absorption lines, reminiscent of KL Dra and 2003aw. The variability selection of SDSS J2047+0008 from the 300 deg^2 of SDSS Stripe 82 presages further AM CVn discoveries in future deep, multicolor, and time-domain surveys such as LSST. The new additions bring the total SDSS yield to seven AM CVns thus far, a substantial contribution to this rare subclass, versus the dozen previously known.Comment: 19 pages, 5 figures, 1 table; submitted to A

Two Rare Magnetic Cataclysmic Variables with Extreme Cyclotron Features Identified in the Sloan Digital Sky Survey

Two newly identified magnetic cataclysmic variables discovered in the Sloan Digital Sky Survey (SDSS), SDSSJ155331.12+551614.5 and SDSSJ132411.57+032050.5, have spectra showing highly prominent, narrow, strongly polarized cyclotron humps with amplitudes that vary on orbital periods of 4.39 and 2.6 hrs, respectively. In the former, the spacing of the humps indicates the 3rd and 4th harmonics in a magnetic field of ~60 MG. The narrowness of the cyclotron features and the lack of strong emission lines imply very low temperature plasmas and very low accretion rates, so that the accreting area is heated by particle collisions rather than accretion shocks. The detection of rare systems like these exemplifies the ability of the SDSS to find the lowest accretion rate close binaries.Comment: Accepted for publication in the Astrophysical Journal, vol. 583, February 1, 2003; slight revisions and additions in response to referee's comments; 17 pages, 6 figures, AASTeX v4.