The Fornax cluster provides a uniquely compact laboratory in which to study the detailed history of early-type galaxies and the role played by the environment in driving their evolution and their ...transformation from late-type galaxies. Using the superb capabilities of the Multi Unit Spectroscopic Explorer on the Very Large Telescope, high-quality integral-field spectroscopic data were obtained for the inner regions of all the bright (mB ≤ 15) galaxies within the virial radius of Fornax. The stellar haloes of early-type galaxies are also covered out to about four effective radii. State-of-the-art stellar dynamical and population modelling allows characterising the disc components of fast-rotating early-type galaxies, constraining radial variations in the stellar initial-mass functions and measuring the stellar age, metallicity, and α-element abundance of stellar haloes in cluster galaxies. This paper describes the sample selection, observations, and overall goals of the survey, and provides initial results based on the spectroscopic data, including the detailed characterisation of stellar kinematics and populations to large radii; decomposition of galaxy components directly via their orbital structure; the ability to identify globular clusters and planetary nebulae, and derivation of high-quality emission-line diagnostics in the presence of complex ionised gas.
ABSTRACT
Hot atmospheres pervading galaxy clusters, groups, and early-type galaxies are rich in metals, produced during epochs and diffused via processes that are still to be determined. While this ...enrichment has been routinely investigated in clusters, metals in lower mass systems are more challenging to probe with standard X-ray exposures and spectroscopy. In this paper, we focus on very deep XMM–Newton (∼350 ks) observations of NGC 1404, a massive elliptical galaxy experiencing ram-pressure stripping of its hot atmosphere while infalling towards the centre of the Fornax cluster, with the aim to derive abundances through its hot gas extent. Importantly, we report the existence of a new fitting bias – the ‘double Fe bias’ – leading to an underestimate of the Fe abundance when two thermal components cannot realistically model the complex temperature structure present in the outer atmosphere of the galaxy. Contrasting with the ‘metal conundrum’ seen in clusters, the Fe and Mg masses of NGC 1404 are measured 1–2 orders of magnitude below what stars and supernovae could have reasonably produced and released. In addition, we note the remarkable Solar abundance ratios of the galaxy’s halo, different from its stellar counterpart but similar to the chemical composition of the ICM of rich clusters. Completing the clusters regime, all these findings provide additional support towards a scenario of early enrichment, at play over two orders of magnitude in mass. A few peculiar and intriguing features, such as a possible double metal peak as well as an apparent ring of enhanced Si near the galaxy core, are also discussed.
We present the emission-line fluxes and kinematics of 48 representative elliptical and lenticular galaxies obtained with our custom-built integral-field spectrograph, SAURON, operating on the William ...Herschel Telescope. Hβ, O iiiλλ4959,5007 and N iλλ5198,5200 emission lines were measured using a new procedure that simultaneously fits both the stellar spectrum and the emission lines. Using this technique we can detect emission lines down to an equivalent width of 0.1 Å set by the current limitations in describing galaxy spectra with synthetic and real stellar templates, rather than by the quality of our spectra. Gas velocities and velocity dispersions are typically accurate to within 14 and 20 km s−1, respectively, and at worse to within 25 and 40 km s−1. The errors on the flux of the O iii and Hβ lines are on average 10 and 20 per cent, respectively, and never exceed 30 per cent. Emission is clearly detected in 75 per cent of our sample galaxies, and comes in a variety of resolved spatial distributions and kinematic behaviours. A mild dependence on the Hubble type and galactic environment is observed, with higher detection rates in lenticular galaxies and field objects. More significant is the fact that only 55 per cent of the galaxies in the Virgo cluster exhibit clearly detected emission. The ionized-gas kinematics is rarely consistent with simple coplanar circular motions. However, the gas almost never displays completely irregular kinematics, generally showing coherent motions with smooth variations in angular momentum. In the majority of the cases, the gas kinematics is decoupled from the stellar kinematics, and in half of the objects this decoupling implies a recent acquisition of gaseous material. Over the entire sample however, the distribution of the mean misalignment values between stellar and gaseous angular momenta is inconsistent with a purely external origin. The distribution of kinematic misalignment values is found to be strongly dependent on the apparent flattening and the level of rotational support of galaxies, with flatter, fast rotating objects hosting preferentially corotating gaseous and stellar systems. In a third of the cases, the distribution and kinematics of the gas underscore the presence of non-axisymmetric perturbations of the gravitational potential. Consistent with previous studies, the presence of dust features is always accompanied by gas emission while the converse is not always true. A considerable range of values for the O iii/Hβ ratio is found both across the sample and within single galaxies. Despite the limitations of this ratio as an emission-line diagnostic, this finding suggests either that a variety of mechanisms is responsible for the gas excitation in E and S0 galaxies or that the metallicity of the interstellar material is quite heterogeneous.
Abstract
The newest generation of integral field unit spectrographs brings three-dimensional mapping of nearby galaxies one step closer. While the focus up to this point was mostly on stars and ...ionized gas, it is also possible to look at dust in a new, more complete way. Using MUSE science verification observations of NGC 5626, we map the interstellar matter in this dusty lenticular. We use the resolving power of MUSE to measure the optical attenuation with a spectral resolution of 6.25 Å, at physical scales of 0.1–1 kpc. The integrated attenuation curve of NGC 5626 shows a smooth, slightly steeper than Milky Way and SMC attenuation curves. Several sharp features are superimposed: we measure lower attenuation at spectral emission lines and higher attenuation for the sodium line doublet. No correlation was observed between sodium line strength and reddening by dust on spatially resolved scales. Additionally, the continuum attenuation was found to be independent from the Balmer decrement (tracing ionized gas attenuation). We model and interpret the variations in the attenuation curves of each spatial resolution element of NGC 5626. We find that the amount and distribution of dust along the line of sight is highly degenerate with any variation in the intrinsic extinction law. Our analysis shows that the interstellar matter in NGC 5626 resides in a regular and well-settled disc. Our results preach caution in the application of simple recipes to de-redden global galaxy spectra and underlines the need for more realistic dust geometries when constructing such correction formulas.
We present a convenient, all-in-one framework for the scientific analysis of fully reduced, (integral-field) spectroscopic data. The Galaxy IFU Spectroscopy Tool (GIST) is entirely written in Python ...3 and conducts all the steps from the preparation of input data to the scientific analysis and to the production of publication-quality plots. In its basic set-up, it extracts stellar kinematics, performs an emission-line analysis, and derives stellar population properties from full spectral fitting and via the measurement of absorption line-strength indices by exploiting the well-known pPXF and GandALF routines, where the latter has now been implemented in Python. The pipeline is not specific to any instrument or analysis technique and provides easy means of modification and further development, thanks to its modular code architecture. An elaborate, Python-native parallelisation is implemented and tested on various machines. The software further features a dedicated visualisation routine with a sophisticated graphical user interface. This allows an easy, fully interactive plotting of all measurements, spectra, fits, and residuals, as well as star formation histories and the weight distribution of the models. The pipeline has been successfully applied to both low- and high-redshift data from MUSE, PPAK (CALIFA), and SINFONI, and to simulated data for HARMONI and WEAVE and is currently being used by the TIMER, Fornax3D, and PHANGS collaborations. We demonstrate its capabilities by applying it to MUSE TIMER observations of NGC 1433.
Nuclear star clusters (NSCs) are the densest stellar systems in the Universe and are found in the centres of all types of galaxies. They are thought to form via mergers of star clusters such as ...ancient globular clusters (GCs) that spiral to the centre as a result of dynamical friction or through in situ star formation directly at the galaxy centre. There is evidence that both paths occur, but the relative contribution of either channel and their correlation with galaxy properties are not yet constrained observationally. Our aim was to derive the dominant NSC formation channel for a sample of 25 nucleated galaxies, mostly in the Fornax galaxy cluster, with stellar masses between
M
gal
∼ 10
8
and 10
10.5
M
⊙
and NSC masses between
M
NSC
∼ 10
5
and 10
8.5
M
⊙
. Using Multi-Unit Spectroscopic Explorer data from the Fornax 3D survey and the ESO archive, we derived star formation histories, mean ages, and metallicities of NSCs, and compared them to the host galaxies. In many low-mass galaxies, the NSCs are significantly more metal poor than their hosts, with properties similar to GCs. In contrast, in the massive galaxies we find diverse star formation histories and cases of ongoing or recent in situ star formation. Massive NSCs (> 10
7
M
⊙
) occupy a different region in the mass–metallicity diagram than lower-mass NSCs and GCs, indicating a different enrichment history. We find a clear transition of the dominant NSC formation channel with both galaxy and NSC mass. We hypothesise that while GC accretion forms the NSCs of the dwarf galaxies, central star formation is responsible for the efficient mass build up in the most massive NSCs in our sample. At intermediate masses both channels can contribute. The transition between these formation channels seems to occur at galaxy masses
M
gal
∼ 10
9
M
⊙
and NSC masses
M
NSC
∼ 10
7
M
⊙
.
The 31 brightest galaxies (mB ≤ 15 mag) inside the virial radius of the Fornax cluster were observed from the centres to the outskirts with the Multi Unit Spectroscopic Explorer on the Very Large ...Telescope. These observations provide detailed high-resolution maps of the line-of-sight kinematics, line strengths of the stars, ionised gas reaching 2–3 Re for 21 early-type galaxies, and 1–2 Re for 10 late-type galaxies. The majority of the galaxies are regular rotators, with eight hosting a kinematically distinct core. Only two galaxies are slow rotators. The mean age, total metallicity, and Mg/Fe abundance ratio in the bright central region inside 0.5 Re and in the galaxy outskirts are presented. Extended emission-line gas is detected in 13 galaxies, most of them are late-type objects with wide-spread star formation. The measured structural properties are analysed in relation to the galaxies’ position in the projected phase space of the cluster. This shows that the Fornax cluster appears to consist of three main groups of galaxies inside the virial radius: the old core; a clump of galaxies, which is aligned with the local large-scale structure and was accreted soon after the formation of the core; and a group of galaxies that fell in more recently.
Globular cluster (GC) systems of massive galaxies often show a bimodal colour distribution. This has been interpreted as a metallicity bimodality, created by a two-stage galaxy formation where the ...red, metal-rich GCs were formed in the parent halo and the blue metal-poor GCs were accreted. This interpretation, however, crucially depends on the assumption that GCs are exclusively old stellar systems with a linear colour–metallicity relation (CZR). The shape of the CZR and range of GC ages are currently under debate because their study requires high quality spectra to derive reliable stellar population properties. We determined metallicities with full spectral fitting from a sample of 187 GCs with a high spectral signal-to-noise ratio in 23 galaxies of the Fornax cluster that were observed as part of the Fornax 3D project. The derived CZR from this sample is non-linear and can be described by a piecewise linear function with a break point at (
g
−
z
) ∼ 1.1 mag. The less massive galaxies in our sample (
M
*
< 10
10
M
⊙
) appear to have slightly younger GCs, but the shape of the CZR is insensitive to the GC ages. Although the least massive galaxies lack red, metal-rich GCs, a non-linear CZR is found irrespective of the galaxy mass, even in the most massive galaxies (
M
*
≥ 10
11
M
⊙
). Our CZR predicts narrow unimodal GC metallicity distributions for low mass and broad unimodal distributions for very massive galaxies, dominated by a metal-poor and metal-rich peak, respectively, and bimodal distributions for galaxies with intermediate masses (10
10
≤
M
*
< 10
11
M
⊙
) as a consequence of the relative fraction of red and blue GCs. The diverse metallicity distributions challenge the simple differentiation of GC populations solely based on their colour.
We present our mass estimate of the central black hole in the isolated spiral galaxy NGC 4414. Using natural guide star adaptive optics assisted observations with the Gemini Near-Infrared Integral ...Field Spectrometer (NIFS) and the natural seeing Gemini Multi-Object Spectrographs-North (GMOS), we derived two-dimensional stellar kinematic maps of NGC 4414 covering the central 1.5 arcsec and 10 arcsec, respectively, at a NIFS spatial resolution of 0.13 arcsec. The kinematic maps reveal a regular rotation pattern and a central velocity dispersion dip down to around 105 km s-1. We constructed dynamical models using two different methods: Jeans anisotropic dynamical modeling and axisymmetric Schwarzschild modeling. Both modeling methods give consistent results, but we cannot constrain the lower mass limit and only measure an upper limit for the black hole mass of MBH = 1.56 × 106M⊙ (at 3σ level) which is at least 1σ below the recent MBH−σe relations. Further tests with dark matter, mass-to-light ratio variation and different light models confirm that our results are not dominated by uncertainties. The derived upper limit mass is not only below the MBH−σe relation, but is also five times lower than the lower limit black hole mass anticipated from the resolution limit of the sphere of influence. This proves that via high quality integral field data we are now able to push black hole measurements down to at least five times less than the resolution limit.
ABSTRACT
We combine data from ALMA and MUSE to study the resolved (∼300 pc scale) star formation relation (star formation rate, SFR, versus molecular gas surface density) in cluster galaxies. Our ...sample consists of nine Fornax cluster galaxies, including spirals, ellipticals, and dwarfs, covering a stellar mass range of ∼108.8–1011 M⊙. CO(1-0) and extinction corrected Hα were used as tracers for the molecular gas mass and SFR, respectively. We compare our results with Kennicutt and Bigiel et al. Furthermore, we create depletion time maps to reveal small-scale variations in individual galaxies. We explore these further in FCC290, using the ‘uncertainty principle for star formation’ (Kruijssen & Longmore) to estimate molecular cloud lifetimes, which we find to be short (<10 Myr) in this galaxy. Galaxy-averaged depletion times are compared with other parameters such as stellar mass and cluster-centric distance. We find that the star formation relation in the Fornax cluster is close to those from Kennicutt and Bigiel et al., but overlaps mostly with the shortest depletion times predicted by Bigiel et al. This slight decrease in depletion time is mostly driven by dwarf galaxies with disturbed molecular gas reservoirs close to the virial radius. In FCC90, a dwarf galaxy with a molecular gas tail, we find that depletion times are a factor ≳10 higher in its tail than in its stellar body.
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