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>

The SAURON project – XIII. SAURON–GALEX study of early-type galaxies: the ultraviolet colour–magnitude relations and Fundamental Planes

Jeong, Hyunjin,Yi, Sukyoung K.,Bureau, Martin,Davies, Roger L.,Falcó,n-Barroso, Jesú,s,van de Ven, Glenn,Peletier, Reynier F.,Bacon, Roland,Cappellari, Michele,de Zeeuw, Tim,Emsellem, Eric Blackwell Publishing Ltd 2009 Monthly notices of the Royal Astronomical Society Vol.398 No.4

<P>ABSTRACT</P><P>We present <I>Galaxy Evolution Explorer</I> far-ultraviolet (FUV) and near-ultraviolet (NUV) imaging of 34 nearby early-type galaxies from the SAURON representative sample of 48 E/S0 galaxies, all of which have ground-based optical imaging from the MDM Observatory. The surface brightness profiles of nine galaxies (≈26 per cent) show regions with blue UV−optical colours suggesting RSF. Five of these (≈15 per cent) show blue integrated UV–optical colours that set them aside in the NUV integrated colour–magnitude relation. These are objects with either exceptionally intense and localized NUV fluxes or blue UV−optical colours throughout. They also have other properties confirming they have had RSF, in particular Hβ absorption higher than expected for a quiescent population and a higher CO detection rate. This suggests that residual star formation is more common in early-type galaxies than we are used to believe. NUV blue galaxies are generally drawn from the lower stellar velocity dispersion (σ<SUB>e</SUB> < 200 km s<SUP>−1</SUP>) and thus lower dynamical mass part of the sample. We have also constructed the first UV Fundamental Planes and show that NUV blue galaxies bias the slopes and increase the scatters. If they are eliminated, the fits get closer to expectations from the virial theorem. Although our analysis is based on a limited sample, it seems that a dominant fraction of the tilt and scatter of the UV Fundamental Planes is due to the presence of young stars in preferentially low-mass early-type galaxies. Interestingly, the UV–optical radial colour profiles reveal a variety of behaviours, with many galaxies showing signs of RSF, a central UV-upturn phenomenon, smooth but large-scale age and metallicity gradients and in many cases a combination of these. In addition, FUV−NUV and FUV−<I>V</I> colours even bluer than those normally associated with UV-upturn galaxies are observed at the centre of some quiescent galaxies. Four out of the five UV-upturn galaxies are slow rotators. These objects should thus pose interesting challenges to stellar evolutionary models of the UV upturn.</P>

STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. II. THE SURVEY AND A SYSTEMATIC ANALYSIS OF KINEMATIC ANOMALIES AND ASYMMETRIES

Toloba, E.,Guhathakurta, P.,Peletier, R. F.,Boselli, A.,Lisker, T.,Falcó,n-Barroso, J.,Simon, J. D.,van de Ven, G.,Paudel, S.,Emsellem, E.,Janz, J.,den Brok, M.,Gorgas, J.,Hensler, G.,Laurikaine IOP Publishing 2014 The Astrophysical journal Supplement series Vol.215 No.2

<P>We present spatially resolved kinematics and global stellar populations and mass-to-light ratios for a sample of 39 dwarf early-type (dE) galaxies in the Virgo cluster studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. This sample is representative of the early-type population in the Virgo cluster in the absolute magnitude range -19.0 < M-r < -16.0 and of all morphological subclasses found in this galaxy population. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best-fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). Our sample includes two dEs with kinematically decoupled cores that have been previously reported. We find that 62 +/- 8% (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. We measure age-sensitive (H-beta and H-gamma A) and metallicity sensitive (Fe4668 and Mgb) Lick spectral indices in the LIS-5 angstrom system. This population of galaxies exhibits a wide range of ages and metallicities; we also find that 4 dEs show clear evidence of emission partially filling in the Balmer absorption lines. Finally, we estimate the total masses and dark matter fractions of the dEs and plot them in the mass-size, themass-velocity dispersion, and the fundamental plane scaling relations. The dEs seem to be the bridge between massive early-type galaxies and dSphs, and have a median total mass within the R-e of logM(e) = 9.1 +/- 0.2 and a median dark matter fraction within the R-e of f(DM) = 46 +/- 18%. Any formation model for the dE galaxy class must account for this diversity of kinematic and photometric anomalies and stellar populations.</P>

The SAURON project – XVIII. The integrated UV–line‐strength relations of early‐type galaxies

Bureau, Martin,Jeong, Hyunjin,Yi, Sukyoung K.,Schawinski, Kevin,Houghton, Ryan C. W.,Davies, Roger L.,Bacon, Roland,Cappellari, Michele,de Zeeuw, P. Tim,Emsellem, Eric,Falcó,n‐,Barroso, Je Blackwell Publishing Ltd 2011 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.414 No.3

<P><B>ABSTRACT</B></P><P>Using far‐ultraviolet (FUV) and near‐ultraviolet (NUV) photometry from guest investigator programmes on the <I>Galaxy Evolution Explorer</I> (<I>GALEX</I>) satellite, optical photometry from the MDM Observatory and optical integral‐field spectroscopy from SAURON, we explore the UV–line‐strength relations of the 48 nearby early‐type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well‐defined correlations of the integrated FUV −<I>V</I> and FUV − NUV colours with the integrated Mg <I>b</I> and Hβ absorption line‐strength indices, strongest for FUV − NUV. Correlations with the NUV −<I>V</I> colour, Fe5015 index and stellar velocity dispersion σ are much weaker. These correlations put stringent constraints on the origin of the UV‐upturn phenomenon in early‐type galaxies and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between FUV −<I>V</I> colour and Mg line strength originally publicized by Burstein et al., which we refer to as the ‘Burstein relation’, suggesting a positive dependence of the UV upturn on metallicity. We argue that the scatter in the correlations is real and present mild evidence that a strong UV excess is preferentially present in slow‐rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully crafted sample of more distant early‐type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys.</P>

The SAURON project – XIX. Optical and near‐infrared scaling relations of nearby elliptical, lenticular and Sa galaxies

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>

The SAURON project – XVI. On the sources of ionization for the gas in elliptical and lenticular galaxies

Sarzi, Marc,Shields, Joseph C.,Schawinski, Kevin,Jeong, Hyunjin,Shapiro, Kristen,Bacon, Roland,Bureau, Martin,Cappellari, Michele,Davies, Roger L.,Tim de Zeeuw, P.,Emsellem, Eric,Falcó,n-Barroso Blackwell Publishing Ltd 2010 Monthly notices of the Royal Astronomical Society Vol.402 No.4

<P>ABSTRACT</P><P>Following our study on the incidence, morphology and kinematics of the ionized gas in early-type galaxies, we now address the question of what is powering the observed nebular emission. To constrain the likely sources of gas excitation, we resort to a variety of ancillary data we draw from complementary information on the gas kinematics, stellar populations and galactic potential from the <SMALL>SAURON</SMALL> data, and use the <SMALL>SAURON</SMALL>-specific diagnostic diagram juxtaposing the [O <SMALL>III</SMALL>]λ5007/Hβ and [N <SMALL>I</SMALL>]λλ5197, 5200/Hβ line ratios. We find a tight correlation between the stellar surface brightness and the flux of the Hβ recombination line across our sample, which points to a diffuse and old stellar source as the main contributor of ionizing photons in early-type galaxies, with post-asymptotic giant branch (pAGB) stars being still the best candidate based on ionizing balance arguments. The role of AGN photoionization is confined to the central 2–3 arcsec of an handful of objects with radio or X-ray cores. OB-stars are the dominant source of photoionization in 10 per cent of the <SMALL>SAURON</SMALL> sample, whereas for another 10 per cent the intense and highly ionized emission is powered by the pAGB population associated to a recently formed stellar subcomponent. Fast shocks are not an important source of ionization for the diffuse nebular emission of early-type galaxies since the required shock velocities can hardly be attained in the potential of our sample galaxies. Finally, in the most massive and slowly or non-rotating galaxies in our sample, which can retain a massive X-ray halo, the finding of a spatial correlation between the hot and warm phases of the interstellar medium (ISM) suggests that the interaction with the hot ISM provides an additional source of ionization besides old ultraviolet-bright stars. This is also supported by a distinct pattern towards lower values of the [O <SMALL>III</SMALL>]/Hβ ratio. These results lead us to investigate the relative role of stellar and AGN photoionization in explaining the ionized gas emission observed in early-type galaxies by the Sloan Digital Sky Survey (SDSS). By simulating how our sample galaxies would appear if placed at further distance and targeted by the SDSS, we conclude that only in very few, if any, of the SDSS galaxies which display modest values for the equivalent width of the [O <SMALL>III</SMALL>] line (less than ∼2.4 Å) and low-ionization nuclear emission-line region like [O <SMALL>III</SMALL>]/Hβ values the nebular emission is truly powered by an AGN.</P>