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Falcó,n‐,Barroso, J.,van de Ven, G.,Peletier, R. F.,Bureau, M.,Jeong, H.,Bacon, R.,Cappellari, M.,Davies, R. L.,de Zeeuw, P. T.,Emsellem, E.,Krajnović,, D.,Kuntschner, H.,McDermid, R. Blackwell Publishing Ltd 2011 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.417 No.3
<P><B>ABSTRACT</B></P><P>We present ground‐based MDM Observatory <I>V</I>‐band and <I>Spitzer</I>/InfraRed Array Camera 3.6‐<IMG src='/wiley-blackwell_img/equation/MNR_19372_mu1.gif' alt ='inline image'/>m‐band photometric observations of the 72 representative galaxies of the SAURON survey. Galaxies in our sample probe the elliptical E, lenticular S0 and spiral Sa populations in the nearby Universe, both in field and cluster environments. We perform aperture photometry to derive homogeneous structural quantities. In combination with the SAURON stellar velocity dispersion measured within an effective radius (σ<SUB>e</SUB>), this allows us to explore the location of our galaxies in the colour–magnitude, colour–σ<SUB>e</SUB>, Kormendy, Faber–Jackson and Fundamental Plane scaling relations. We investigate the dependence of these relations on our recent kinematical classification of early‐type galaxies (i.e. slow/fast rotators) and the stellar populations. Slow rotator and fast rotator E/S0 galaxies do not populate distinct locations in the scaling relations, although slow rotators display a smaller intrinsic scatter. We find that Sa galaxies deviate from the colour–magnitude and colour–σ<SUB>e</SUB> relations due to the presence of dust, while the E/S0 galaxies define tight relations. Surprisingly, extremely young objects do not display the bluest (<I>V</I>−[3.6]) colours in our sample, as is usually the case in optical colours. This can be understood in the context of the large contribution of thermally pulsing asymptotic giant branch stars to the infrared, even for young populations, resulting in a very tight (<I>V</I>−[3.6])–σ<SUB>e</SUB> relation that in turn allows us to define a strong correlation between metallicity and σ<SUB>e</SUB>. Many Sa galaxies appear to follow the Fundamental Plane defined by E/S0 galaxies. Galaxies that appear offset from the relations correspond mostly to objects with extremely young populations, with signs of ongoing, extended star formation. We correct for this effect in the Fundamental Plane, by replacing luminosity with stellar mass using an estimate of the stellar mass‐to‐light ratio, so that all galaxies are part of a tight, single relation. The new estimated coefficients are consistent in both photometric bands and suggest that differences in stellar populations account for about half of the observed tilt with respect to the virial prediction. After these corrections, the slow rotator family shows almost no intrinsic scatter around the best‐fitting Fundamental Plane. The use of a velocity dispersion within a small aperture (e.g. <I>R</I><SUB>e</SUB>/8) in the Fundamental Plane results in an increase of around 15 per cent in the intrinsic scatter and an average 10 per cent decrease in the tilt away from the virial relation.</P>
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The SAURON project – XXI. The spatially resolved UV–line strength relations of early‐type galaxies
Jeong, Hyunjin,Yi, Sukyoung K.,Bureau, Martin,Davies, Roger L.,Bacon, Roland,Cappellari, Michele,de Zeeuw, P. Tim,Emsellem, Eric,Falcó,n‐,Barroso, Jesú,s,Krajnović,, Davor,Kunts Blackwell Publishing Ltd 2012 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.423 No.2
<P><B>ABSTRACT</B></P><P>The unexpected rising flux of early‐type galaxies at decreasing ultraviolet (UV) wavelengths is a long‐standing mystery. One important observational constraint is the correlation between UV–optical colours and Mg<SUB>2</SUB> line strengths found by Burstein et al. The simplest interpretation of this phenomenon is that the UV strength is related to the Mg line strength. Under this assumption, we expect galaxies with larger Mg gradients to have larger UV colour gradients. By combining UV imaging from <I>GALEX</I>, optical imaging from MDM and SAURON integral‐field spectroscopy, we investigate the spatially resolved relationships between UV colours and stellar population properties of 34 early‐type galaxies from the SAURON survey sample. We find that galaxies with old stellar populations show tight correlations between the far‐UV (FUV) colours (FUV −<I>V</I> and FUV − NUV) and the Mg <I>b</I> index, Hβ index and metallicity [<I>Z</I>/H]. The equivalent correlations for the Fe5015 index, α‐enhancement [α/Fe] and age are present but weaker. We have also derived logarithmic internal radial colour, <I>measured</I> line strength and <I>derived</I> stellar population gradients for each galaxy and again found a strong dependence of the FUV −<I>V</I> and FUV − NUV colour gradients on both the Mg <I>b</I> line strength and the metallicity gradients for galaxies with old stellar populations. In particular, global gradients of Mg <I>b</I> and [<I>Z</I>/H] with respect to the UV colour [e.g. Δ(Mg <I>b</I>)/Δ(FUV − NUV) and Δ[<I>Z</I>/H]/Δ(FUV − NUV)] across galaxies are consistent with their local gradients within galaxies, suggesting that the global correlations also hold locally. From a simple model based on multiband colour fits of UV upturn and UV‐weak galaxies, we have identified a plausible range of parameters that reproduces the observed radial colour profiles. In these models, the centres of elliptical galaxies, where the UV flux is strong, are enhanced in metals by roughly 60 per cent compared to UV‐weak regions.</P>
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