Tracey Hill

Kent State University | KSU · College of Nursing

The SCUBA-2 Ambitious Sky Survey (SASSy) is composed of shallow 850-μm imaging using the Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) on the James Clerk Maxwell Telescope. Here we describe the extraction of a catalogue of beam-sized sources from a roughly 120 deg² region of the Galactic plane mapped uniformly (to an rms level of about 40...

Triggered star formation around HII regions could be an important process. The Galactic HII region RCW 79 is a prototypical object for triggered high-mass star formation. We take advantage of Herschel data from the surveys HOBYS, "Evolution of Interstellar Dust", and Hi-Gal to extract compact sources in this region, complemented with archival 2MASS...

The scaling relations and star formation laws for molecular cloud complexes (MCCs) in the Milky Way are investigated. MCCs are mostly large (R > 50 pc), massive (~106 ) gravitationally unbound cloud structures. We compare their masses , mass surface densities , radii R, velocity dispersions σ, star formation rates (SFRs), and SFR densities with tho...

We present a comparison of SCUBA-2 850-$\mu$m and Herschel 70--500-$\mu$m observations of the L1495 filament in the Taurus Molecular Cloud with the goal of characterising the SCUBA-2 Gould Belt Survey (GBS) data set. We identify and characterise starless cores in three data sets: SCUBA-2 850-$\mu$m, Herschel 250-$\mu$m, and Herschel 250-$\mu$m spat...

To link the physical and star formation properties of structures ranging from Giant Molecular Clouds (GMCs), to Molecular Cloud Complexes (MCCs), and to Galaxies, we compare the mutual relations between their masses $M$, mass surface densities $\Sigma_{M_{\rm gas}}$, radii $R$, velocity dispersions $\sigma$, star formation rates $SFR$, and SFR dens...

The surroundings of HII regions can have a profound influence on their development, morphology, and evolution. This paper explores the effect of the environment on H II regions in the MonR2 molecular cloud. We aim to investigate the density structure of envelopes surrounding HII regions and to determine their collapse and ionisation expansion ages....

We present the first results from the MALT-45 (Millimetre Astronomer's Legacy Team-45 GHz) Galactic Plane survey. We have observed 5 square degrees (l = 330°–335°, b = ±0 $_{.}^{\circ}$5) for spectral lines in the 7 mm band (42–44 and 48–49 GHz), including CS (1–0), class I CH3OH masers in the 7(0,7)–6(1,6) A+ transition and SiO (1–0) v = 0, 1, 2,...

Context. Star formation efficiency (SFE) theories are currently based on statistical distributions of turbulent cloud structures and a simple model of star formation from cores. They remain poorly tested, especially at the highest densities. Aims. We investigate the effects of gas density on the SFE through measurements of the core formation effic...

Molecular cloud complexes are structures of molecular gas with sizes up to 50-200 pc. The multi-wavelength data of Herschel allow us to construct column density maps. From these maps, we discover prominent filamentary structures (N-H2 > 10(23) cm(-2)), which we call "ridges". We use the number of burgeoning YSOs detected in submm wavelengths with H...

Observations of the high-mass star formation region NGC 7538 taken with the Herschel Space Observatory were made at 70, 160, 250, 350, and 500 micron as part of the Herschel imaging study of OB Young Stellar objects (HOBYS) Key Programme. Within the one square degree field, we identify 780 dense sources and classify 224 of those. With the intention...

We characterize the Millimeter Astronomy Legacy Team 90 GHz (MALT90) Survey and the Mopra telescope at 90 GHz. We combine repeated position-switched observations of the source G300.968+01.145 with a map of the same source in order to estimate the pointing reliability of the position-switched observations and, by extension, the MALT90 survey; we est...

We have studied the opacity of dust grains at submillimeter wavelengths by estimating the optical depth from imaging at 160, 250, 350, and 500 um from the Herschel Gould Belt Survey and comparing this to a column density obtained from the 2MASS-derived color excess E(J-Ks). Our main goal was to investigate the spatial variations of the opacity due...

We present the first Herschel PACS and SPIRE results of the Vela C molecular complex in the far-infrared and submillimetre regimes at 70, 160, 250, 350, and 500 um, spanning the peak of emission of cold prestellar or protostellar cores. Column density and multi-resolution analysis (MRA) differentiates the Vela C complex into five distinct sub-regio...

We propose an ammonia spectral line study to determine the kinetic temperatures in the dense cores of the G333 giant molecular cloud complex. The temperatures will be used to constrain spectral energy distribution modelling of the dense cores to determine the luminosity and mass. Ammonia is an excellent molecular cloud thermometer and is perfectly...

We propose to image a small sample of 10 millimetre continuum sources identified in a 1.2mm continuum survey by Hill et al. (2005). These sources are devoid of typical indications of massive star formation such as methanol maser and radio continuum sources. Subsequent submillimetre continuum observations, Parkes ammonia observations and spectral en...

We propose an NH3 spectral line study of southern massive star formation sources that have been mapped in millimetre continuum emission using the SIMBA bolometer on the SEST. Following a multiwavelength investigation into these cores, using followup and existing submillimetre continuum observations as well as archival infrared data, we have drawn s...

We propose an SiO, HCN/HNC and HCO+ spectral line study of southern massive star formation sources that were previously identified in a millimetre continuum emission survey on the SEST. These sources are found offset from and devoid of methanol maser and an UC HII sources which typically trace young massive stars. Subsequent SCUBA observations on t...

Although methanol masers are known to be excellent tracers of massive star formation, and especially of their kinematics and geometry, it is still unclear exactly which conditions and structures the masers trace. In order to investigate this, we propose to observe the dust and/or radio continuum related to four methanol maser sources for which we h...

We present the results of spectral energy distribution analysis for 162 of the 405 sources reported in the SIMBA survey of Hill et al. (2005). The fits reveal source specific parameters including: the luminosity, mass, temperature, H$_2$ number density, the surface density and the luminosity-to-mass ratio. Each of these parameters are examined with...

We propose a millimetre spectral line study of southern massive star formation sources that were previously identified in a millimetre continuum emission survey on the SEST. These sources are found offset from, and are devoid of, methanol maser and UC Hriptsize II regions, which typically trace young massive stars. In subsequent SCUBA observations...

We report millimetre continuum observations of more than 300 massive star forming complexes collected during a survey conducted on the SEST telescope at 1.2mm. These complexes were traced using CH3OH maser and UC HII region positions reported by Walsh et al in a survey conducted in 1998. Methanol masers and UC HII regions are considered tracers of...

We have used the 22m Mopra millimetre wave telescope to identify massive young stellar objects in their hot molecular core phase . A sample of 82 sources associated with galactic methanol masers was chosen with the help of IRAS SCUBA and SEST images as potential candidates. Here we report our observations of these sources using the 3.26mm transitio...

Methanol masers have now been recognised as a likely exclusive signpost of massive star formation. More interestingly radio observations toward a large source sample have shown that methanol masers are isolated from traditional signposts of massive star formation such as ultra-compact HII (UCHII) regions. A recent Mopra survey toward the so-called...