arXiv subjects

R. Tuffs

Publications and source records attributed to R. Tuffs.

25 records · Page 2Linked to original sources

arXiv2010

Galaxy and Mass Assembly (GAMA): Dust obscuration in galaxies and their recent star formation histories

We present self-consistent star formation rates derived through pan-spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Halpha, [O{II}] and UV luminosities. These corrections are applied to a sample of 31,508 galaxies from the GAMA survey at z < 0.35. We consider several different obscuration curves, including those of Milky Way, Calzetti (2001) and Fischera and Dopita (2005) curves and their effects on the observed luminosities. At the core of this technique is the observed Balmer decrement, and we provide a prescription to apply optimal obscuration corrections using the Balmer decrement. We carry out an analysis of the star formation history (SFH) using stellar population synthesis tools to investigate the evolutionary history of our sample of galaxies as well as to understand the effects of variation in the Initial Mass Function (IMF) and the effects this has on the evolutionary history of galaxies. We find that the Fischera and Dopita (2005) obscuration curve with an R_{v} value of 4.5 gives the best agreement between the different SFR indicators. The 2200A feature needed to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission. We also find that the UV dust obscuration is strongly dependent on the SFR.

astro-ph.CO↗

arXiv2010

The Herschel-ATLAS: Evolution of the 250um luminosity function out to z=0.5

We have determined the luminosity function of 250um-selected galaxies detected in the ~14 sq.deg science demonstration region of the Herschel-ATLAS project out to a redshift of z=0.5. Our findings very clearly show that the luminosity function evolves steadily out to this redshift. By selecting a sub-group of sources within a fixed luminosity interval where incompleteness effects are minimal, we have measured a smooth increase in the comoving 250um luminosity density out to z=0.2 where it is 3.6+1.4-0.9 times higher than the local value.

astro-ph.CO↗

arXiv2010

Herschel-ATLAS: Dust temperature and redshift distribution of SPIRE and PACS detected sources using submillimetre colours

We present colour-colour diagrams of detected sources in the Herschel-ATLAS Science Demonstration Field from 100 to 500 microns using both PACS and SPIRE. We fit isothermal modified black bodies to the spectral energy distribution (SED) to extract the dust temperature of sources with counterparts in Galaxy And Mass Assembly (GAMA) or SDSS surveys with either a spectroscopic or a photometric redshift. For a subsample of 330 sources detected in at least three FIR bands with a significance greater than 3 $σ$, we find an average dust temperature of $(28 \pm 8)$K. For sources with no known redshift, we populate the colour-colour diagram with a large number of SEDs generated with a broad range of dust temperatures and emissivity parameters, and compare to colours of observed sources to establish the redshift distribution of this sample. For another subsample of 1686 sources with fluxes above 35 mJy at 350 microns and detected at 250 and 500 microns with a significance greater than 3$σ$, we find an average redshift of $2.2 \pm 0.6$.

astro-ph.CO↗

arXiv2009

Powerful H$_2$ Line-cooling in Stephan's Quintet : I - Mapping the Significant Cooling Pathways in Group-wide Shocks

We present results from the mid-infrared spectral mapping of Stephan's Quintet using the Spitzer Space Telescope. A 1000 km/s collision has produced a group-wide shock and for the first time the large-scale distribution of warm molecular hydrogen emission is revealed, as well as its close association with known shock structures. In the main shock region alone we find 5.0 $\times10^{8}$ M$_{\odot}$ of warm H$_2$ spread over $\sim$ 480 kpc$^2$ and additionally report the discovery of a second major shock-excited H$_2$ feature. This brings the total H$_2$ line luminosity of the group in excess of 10$^42$ erg/s. In the main shock, the H$_2$ line luminosity exceeds, by a factor of three, the X-ray luminosity from the hot shocked gas, confirming that the H$_2$-cooling pathway dominates over the X-ray. [Si II]34.82$μ$m emission, detected at a luminosity of 1/10th of that of the H$_2$, appears to trace the group-wide shock closely and in addition, we detect weak [FeII]25.99$μ$m emission from the most X-ray luminous part of the shock. Comparison with shock models reveals that this emission is consistent with regions of fast shocks (100 < $V_{s}$ < 300 km/s) experiencing depletion of iron and silicon onto dust grains. Star formation in the shock (as traced via ionic lines, PAH and dust emission) appears in the intruder galaxy, but most strikingly at either end of the radio shock. The shock ridge itself shows little star formation, consistent with a model in which the tremendous H$_{2}$ power is driven by turbulent energy transfer from motions in a post-shocked layer. The significance of the molecular hydrogen lines over other measured sources of cooling in fast galaxy-scale shocks may have crucial implications for the cooling of gas in the assembly of the first galaxies.

astro-ph.CO↗

arXiv2009

The Herschel ATLAS

The Herschel ATLAS is the largest open-time key project that will be carried out on the Herschel Space Observatory. It will survey 510 square degrees of the extragalactic sky, four times larger than all the other Herschel surveys combined, in five far-infrared and submillimetre bands. We describe the survey, the complementary multi-wavelength datasets that will be combined with the Herschel data, and the six major science programmes we are undertaking. Using new models based on a previous submillimetre survey of galaxies, we present predictions of the properties of the ATLAS sources in other wavebands.

astro-ph.CO↗

arXiv2001

Modeling the spectral energy distribution of galaxies. II. Disk opacity and star formation in 5 edge-on spirals

Using tools previously described and applied to the prototype galaxy NGC 891, we model the optical to far-infrared spectral energy distributions (SED) of four additional edge-on spiral galaxies, namely NGC 5907, NGC 4013, UGC 1082 and UGC 2048. Comparing the model predictions with IRAS and, where available, sub-millimeter and millimeter observations, we determine the respective roles of the old and young stellar populations in grain heating. In all cases, the young population dominates, with the contribution of the old stellar population being at most 40%, as previously found for NGC 891. After normalization to the disk area, the massive star-formation rate (SFR) derived using our SED modeling technique, which is primarily sensitive to the non-ionizing ultraviolet output from the young stellar population, lies in the range 7e-4 - 2e-2 M_sun * yr^-1 * kpc^-2. This is consistent with normalized SFRs derived for face-on galaxies of comparable surface gas densities from H_alpha observations. Though the most active star-forming galaxy of the five in absolute terms, NGC 891 is not an exceptional system in terms of its surface density in SFR.

astro-ph↗

arXiv1996

An ISOPHOT of the disk of galaxy NGC 6946: 60 micron infrared and radio continuum correlation

We use the ISOPHOT 60 micron image of Tuffs et al. (1996) to study the 60 micron light distribution and its correlation with radio continuum within the disk of spiral galaxy NGC6946, and to resolve the long-standing IRAS controversy as to whether the infrared-to-radio continuum ratio, Q, decreases radially out in galaxy disks. Our main results are: (1) The disk at 60 microns also appears to follow an exponential fall-off. Its e-folding scale-length lies between 1'.3 and an upper limit of 1'.9, obtained from the mean radial profile between 1'.5 and 4' in radius. This scale length is smaller than that derived from the radio continuum data at either 20cm or 6cm, with or without the thermal component removed, at a significance level of >~ 2 sigma. From 1'.5 to 4' in radius, the 60 micron -to-radio continuum surface brightness ratio, Q, decreases by a factor of 1.5 to 1.7 on average. These quantitative results agree with that of Marsh & Helou (1995) using IRAS HiRes data, but not with that of Fitt et al. (1992) based on IRAS CPC data. Our results also fit into the picture of the radio disk as a ``smeared'' version of the infrared disk, but are not consistent with the picture in which the variation of Q is a result of the thermal and non-thermal radio components having two distinct, constant values of the infrared-to-radio ratio.

astro-ph↗