arXiv subjects

L. Dunne

Publications and source records attributed to L. Dunne.

165 records · Page 10Linked to original sources

arXiv2000

Constraining the Radio-Submm Redshift Indicator using data from the SCUBA Local Universe Galaxy Survey

Many of the faint submm sources uncovered by deep SCUBA surveys still remain unidentified at most, if not all other wavelengths. The most successful method so far of obtaining accurate positions and hence allowing more secure identifications has been to use centimetre wavelength imaging with the VLA. This has led to a tempting approach for obtaining redshift estimates for this population (Carilli & Yun 1999,2000), which relies on the tight FIR-radio relationship and takes advantage of the steep spectral slope in the submm. In this paper we use the submm data from the SCUBA Local Universe Galaxy Survey (SLUGS) to estimate the usefulness of, and the uncertainties in, the radio-submm redshift estimator. We investigate the dependencies of the submm-radio spectral index on various galaxy properties and find that there is no significant trend with dust temperature or 850 micron luminosity. The ratio of 850 micron/1.4 GHz flux was found to decrease with increasing radio and FIR luminosity, and we propose that this is due to a component of the dust not associated with recent star formation but which is instead heated to 15-20 K by the general interstellar radiation field.

astro-ph↗

arXiv2000

High spatial resolution observations of CUDSS14A: a SCUBA-selected Ultraluminous galaxy at high redshift

We present a high-resolution millimetre interferometric image of the brightest SCUBA-selected galaxy from the Canada-UK deep SCUBA survey (CUDSS). We make a very clear detection at 1.3 mm, but fail to resolve any structure in the source. The interferometric position is within 1.5 arcsec of the SCUBA 850 $μ$m centroid, and also within 1.5 arcsec of a 44 $μ$Jy radio source and a very faint, extremely red galaxy which we had previously identified as the submillimetre source. We also present new optical and infrared imaging, and infrared spectroscopy of this source. We model the overall spectral energy distribution and conclude that it lies within the redshift range 2$< z < 4.5$. The submm/FIR luminosity of CUDSS14A is very weakly dependent on redshift within the constrained range, and is roughly 4$\times10^{12}$ L$_\odot$ (for H$_0$=75 and an assumed Arp220-like spectrum), which implies a star-formation rate $\sim$1000 M$_\odot$ yr$^{-1}$. We derive an approximate gas mass of $\sim 10^{10}$ M$_\odot$ which would imply the current star-forming activity cannot be sustained for longer than about 10 million years. With the present data however we are unable to rule out a significant AGN contribution to the total luminosity.

astro-ph↗

arXiv2000

The SCUBA Local Universe Galaxy Survey I: First Measurements of the Submillimetre Luminosity and Dust Mass Functions

We have used SCUBA to observe a complete sample of 104 galaxies selected at 60 microns from the IRAS BGS and we present here the 850 micron measurements. Fitting the 60,100 and 850 micron fluxes with a single temperature dust model gives the sample mean temperature T=36 K and beta = 1.3. We do not rule out the possibility of dust which is colder than this, if a 20 K component was present then our dust masses would increase by factor 1.5-3. We present the first measurements of the luminosity and dust mass functions, which were well fitted by Schechter functions (unlike those 60 microns). We have correlated many global galaxy properties with the submillimetre and find that there is a tendancy for less optically luminous galaxies to contain warmer dust and have greater star formation efficiencies (cf. Young 1999). The average gas-to-dust ratio for the sample is 581 +/- 43 (using both atomic and molecular hydrogen), significantly higher than the Galactic value of 160. We believe this discrepancy is due to a cold dust component at T < 20 K. There is a suprisingly tight correlation between dust mass and the mass of molecular hydrogen as estimated from CO measurements, with an intrinsic scatter of ~50%.

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