Main Research Interests:

My primary research interest is in the area of massive star formation, which is an area that underpins many fields of astrophysics and provides an opportunity to understand many physical processes contributing.

Massive stars (>8 Msun and 103 Lsun) have a profound impact on their environment. They shape the interstellar medium (ISM) with their strong stellar winds and ionizing radiation, regulating star (and planet) formation, and ultimately drive the chemical and physical evolution of their host galaxies. Furthermore, the light from massive stars dominates the emission from galaxies, and therefore galaxy models depend on various assumptions that are made about massive star formation such as the star formation rate (SFR) or the universality of the initial mass function (IMF). If we are to understand the evolution of galaxies over cosmic timescales we must first understand the formation and early evolution of massive stars.

The Milky Way offers a unique template with which to study these processes. Unlike more distant galaxies where observations are restricted to global properties integrated over entire complexes, within the Milky Way we can resolve individual star-forming regions in far greater detail. Moreover, the Milky Way consists of a large range of environments including the Galactic centre with its extreme UV-radiation and cosmic ray fluxes, intense star forming regions (e.g., W43 & W51; often described as "mini-starbursts") and the low-metallicity ISM of the outer Galaxy. All of these environments have close extragalactic analogues and so allow us to test the assumptions used in galaxy formation and evolution models.

My research aims to exploit a large number of Galactic plane continuum and spectral-line multi-wavelength surveys to quantify the star formation within all massive dense clumps (>103 Msun) in the Galactic plane. The main aims are to: 1) determine the evolutionary sequence for massive star formation and the statistical lifetimes for each stage and the initial conditions; and 2) to use the Galactic distribution of these massive star forming clumps, and their properties, to evaluate the role the spiral arms and environment plays in the star formation process.

Project Overview:

The ATLASGAL Project

APEX Telescope Large Area Survey of the Galaxy (ATLAS- GAL) is an unbiased 870m survey covering 420 sq.degs of the inner Galactic plane (280o < l < 60o, |b| < 1.5o). This survey is sensitive to dust emission from all massive clumps located across the inner Galaxy (>1,000 Msun). We have identify of 10,000 distinct compact sources and this is likely to include 70% of all massive star forming (MSF) regions in the Galaxy (Contreras et al. 2013; Csengeri et al. 2014). This survey provides an unprecedented census of the cold and dense en- vironments and is the ideal starting point to identify a complete sample of MSF clumps.

Fig. 1. Fraction of the Galactic plane surveyed by ATLASGAL (red), combined with GLIMPSE mid-infrared emission (blue and green).

We have correlated these clumps with massive star formation tracers found in the literature (see Fig. 1); this has resulted in a sample of 1300 MSF clumps, that cover a wide range of evolutionary stages, and use this to investigate their distribution with respect to the spiral arms (see Fig. 2).

Fig. 2. Upper and lower left panels show the Galactic distribution of massive star forming clumps identified by combining ATLASGAL with other Galactic plane surveys. The upper, middle and lower right panels show examples of methanol maser, massive YSOs and compact HII region associations, respectively.

We have produced the largest and most well-characterised sample of MSF clumps located across the inner Galaxy (Urquhart et al. 2014). Statistical analysis of this sample will produce significant breakthroughs in our understanding of massive star formation and the role of galaxies as engines of star formation. The main goals for future work are: 1) to establish an evolutionary sequence for MSF clumps; 2) to determine the 3D structure of the Galaxy and investigate the role of filaments and spiral arms in the star formation process; 3) and to derive statistical properties of high-mass star formation that can be compared with the properties measured in nearby galaxies.

Press Releases:

ATLASGAL Survey of Milky Way Completed

Mapping Cold Dust in the Universe

Hidden nurseries in the Milky Way

The Red MSX Source Survey

The Red MSX Source (RMS) survey has identified a large well-selected and well-characterised sample of young massive stars (e.g., distance and luminosity). By combining infrared, millimetre and radio wavelength observations with complementary archival data we have identified ~1800 MYSOs and ultra-compact HII regions located throughout the Galactic plane (b < 5o) - an order of magnitude larger than previously available.

Press Releases:

Massive stars mark out Milky Way's 'missing' arms