http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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 H <small>i</small> environment of counter‐rotating gas hosts: gas accretion from cold gas blobs
Chung, Aeree,Bureau, Martin,van Gorkom, J. H.,Koribalski, Bä,rbel Blackwell Publishing Ltd 2012 Monthly notices of the Royal Astronomical Society Vol.422 No.2
<P><B>ABSTRACT</B></P><P>We probe the H <SMALL>i</SMALL> properties and the gas environments of three early‐type barred galaxies harbouring counter‐rotating ionized gas: NGC 128, NGC 3203 and NGC 7332. Each system has one or more optically identified galaxy at a similar or as yet unknown redshift within a 50‐kpc projected radius. Using H <SMALL>i</SMALL> synthesis imaging data, we investigate the hypothesis that the counter‐rotating gas in these galaxies has been accreted from their neighbours. In NGC 128 and NGC 3203, we find 9.6 × 10<SUP>7</SUP> and 2.3 × 10<SUP>8</SUP> M<SUB>⊙</SUB> of H <SMALL>i</SMALL>, respectively, covering almost the entire stellar bodies of dwarf companions that appear physically connected. Both the H <SMALL>i</SMALL> morphology and kinematics are suggestive of tidal interactions. In NGC 7332, we do not find any directly associated H <SMALL>i</SMALL>. Instead, NGC 7339, a neighbour of a comparable size at about 10 kpc, is found with 8.9 × 10<SUP>8</SUP> M<SUB>⊙</SUB> of H <SMALL>i</SMALL> gas. More recently in a single dish observation, however, another group discovered a large H <SMALL>i</SMALL> structure which seems to be an extension of NGC 7339’s H <SMALL>i</SMALL> disc and also covers NGC 7332. All these observations thus suggest that H <SMALL>i</SMALL> gas is being accreted in these three galaxies from their companions, which is likely responsible for the kinematically decoupled gas component present in their central region. In particular, the dynamical friction time‐scales of the nearest neighbours with H <SMALL>i</SMALL> gas of NGC 128 and NGC 3203 are comparable to their orbital time‐scales around the counter‐rotators, several ∼10<SUP>8</SUP> yr, implying that those neighbours will likely soon merge with the primary galaxies, fuelling them with gas. NGC 7332 also appears to be in the merging process with its neighbour through the common H <SMALL>i</SMALL> envelope. Besides, we find some other potential gas donors around NGC 128 and NGC 7332: two H <SMALL>i</SMALL>‐rich galaxies with <IMG src='/wiley-blackwell_img/equation/MNR_20679_mu1.gif' alt ='inline image'/> and 2.5 × 10<SUP>9</SUP> M<SUB>⊙</SUB> at a distance of ≈67 kpc from NGC 128 and two dwarf systems with <I>M</I><SUB>HI</SUB>= 3.9 × 10<SUP>7</SUP> and 7.4 × 10<SUP>7</SUP> M<SUB>⊙</SUB> at ≲100 kpc from NGC 7332. Among the seven H <SMALL>i</SMALL> features identified in this study, three of them are associated with dwarf galaxies, two of which have only been recently identified in a blind survey, while the third one is still not catalogued at optical wavelengths. Considering the incompleteness of existing studies of the faint dwarf galaxy population both in the optical and in H <SMALL>i</SMALL>, accretion from cold gas blobs, presumably gas‐rich dwarfs, is expected to occur even more frequently than what is inferred from such cases that have been observed to date.</P>
The first UV fundamental plane and evidence of star formation in early-type galaxies
Jeong, Hyun-Jin,Yi, Suk-Young,Bureau, Martin,Davies, Roger L. 한국우주과학회 2009 한국우주과학회보 Vol.18 No.2
We present GALEX (Galaxy Evolution Explorer) far (FUV) and near (NUV) ultraviolet imaging of 34 nearby early-type galaxies from the SAURON representative sample of 48E/S0 galaxies, all of which have ground-based optical imaging from the MDM Observatory. T
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>