12 research outputs found
Abundance and temperature distributions in the hot intra-cluster gas of Abell 4059
Using the EPIC and RGS data from a deep (~200 ks) XMM-Newton observation, we
investigate the temperature structure (kT and sigma_T ) and the abundances of 9
elements (O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni) of the intra-cluster medium
(ICM) in the nearby (z=0.046) cool-core galaxy cluster Abell 4059. Next to a
deep analysis of the cluster core, a careful modelling of the EPIC background
allows us to build radial profiles up to 12' (~650 kpc) from the core. Probably
because of projection effects, the temperature ICM is found not to be in single
phase, even in the outer parts of the cluster. The abundances of Ne, Si, S, Ar,
Ca and Fe, but also O are peaked towards the core. Fe and O are still
significantly detected in the outermost annuli; suggesting that the enrichment
by both type Ia and core-collapse SNe started in the early stages of the
cluster formation. However, the particularly high Ca/Fe ratio that we find in
the core is not well reproduced by the standard SNe yield models. Finally, 2-D
maps of temperature and Fe abundance are presented and confirm the existence of
a denser, colder, and Fe-rich ridge southwest of the core, previously observed
by Chandra. The origin of this asymmetry in the hot gas of the cluster core is
still unclear, but might be explained by a past intense ram-pressure stripping
event near the central cD galaxy.Comment: 17 pages, 13 figures, accepted for publication in A&
Chemical abundances in the outskirts of nearby galaxy groups measured with joint Suzaku and Chandra observations
We report results from deep Suzaku and mostly snapshot Chandra observations
of four nearby galaxy groups: MKW4, Antlia, RXJ1159+5531, and ESO3060170. Their
peak temperatures vary over 2-3 keV, making them the smallest systems with gas
properties constrained to their viral radii. The average Fe abundance in the
outskirts (R 0.25R) of their intragroup medium (IGrM) is with = 14 for 12 degrees of freedom,
which is remarkably uniform and strikingly similar to that of massive galaxy
clusters, and is fully consistent with the numerical predictions from the
IllustrisTNG cosmological simulation. Our results support an early-enrichment
scenario among galactic systems over an order of magnitude in mass, even before
their formation. When integrated out to R, we start to see a tension
between the measured Fe content in ICM and what is expected from supernovae
yields. We further constrain their O, Mg, Si, S, and Ni abundances. The
abundance ratios of those elements relative to Fe are consistent with the
predictions (if available) from IllustrisTNG. Their Type Ia supernovae fraction
varies between 14%-21%. A pure core collapsed supernovae enrichment at group
outskirts can be ruled out. Their cumulative iron-mass-to-light ratios within
R are half that of the Perseus cluster, which may imply that galaxy
groups do not retain all of their enriched gas due to their shallower
gravitational potential wells, or that groups and clusters may have different
star formation histories.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Societ
How do atomic code uncertainties affect abundance measurements in the intracluster medium?
Accurate chemical abundance measurements of X-ray-emitting atmospheres pervading massive galaxies, galaxy groups, and clusters provide essential information on the star formation and chemical enrichment histories of these large-scale structures. Although the collisionally ionized nature of the intracluster medium (ICM) makes these abundance measurements relatively easy, the underlying spectral models can rely on different atomic codes, which brings additional uncertainties on the inferred abundances. Here we provide a simple, yet comprehensive comparison between the codes SPEXACT v3.0.5 (cie model) and AtomDB v3.0.9 (vapec model) in the case of moderate, charged-coupled device-like resolution spectroscopy. We show that in cool plasmas (kT âČ 2âkeV), systematic differences up to âŒ20% for the Fe abundance and âŒ45% for the O/Fe, Mg/Fe, Si/Fe, and S/Fe ratios may still occur. Importantly, these discrepancies are also found to be instrument-dependent, at least for the absolute Fe abundance. Future improvements in these two codes will be necessary to better address questions on ICM enrichment
Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals
The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it is continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) supernovae since the major epoch of star formation (z ~ 2-3). The cluster/group enrichment history and the mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of SNIa and SNcc products within the ICM. In this paper, we use deep XMM-Newton/EPIC observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (CHEERS) to constrain the average radial O, Mg, Si, S, Ar, Ca, Fe, and Ni abundance profiles. The radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. We find an overall decrease of the Fe abundance with radius out to ~ and ~ for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. The average radial profiles of all the other elements (X) are also centrally peaked and, when rescaled to their average central X/Fe ratios, follow well the Fe profile out to at least ~0.5. Using two sets of SNIa and SNcc yield models reproducing well the X/Fe abundance pattern in the core, we find that, as predicted by recent simulations, the relative contribution of SNIa (SNcc) to the total ICM enrichment is consistent with being uniform at all radii, both for clusters and groups. In addition to implying that the central metal peak is balanced between SNIa and SNcc, our results suggest that the enriching SNIa and SNcc products must share the same origin, and that the delay between the bulk of the SNIa and SNcc explosions must be shorter than the timescale necessary to diffuse out the metals
Expanding on the Fundamental Metallicity Relation in Dwarf Galaxies with MUSE
The mass-metallicity relation (MZR) represents one of the most important
scaling relations in the context of galaxy evolution, comprising a positive
correlation between stellar mass and metallicity (Z). The fundamental
metallicity relation (FMR) introduces a new parameter, the star formation rate
(SFR), in the dependence. While several studies found that Z is anti-correlated
with the SFR at fixed mass, the validity of this statement has been questioned
extensively and no widely-accepted consensus has been reached yet. With this
work, we investigate the FMR in nine nearby, spatially-resolved, dwarf
galaxies, using gas diagnostics on integral-field spectroscopic data of the
Multi Unit Spectroscopic Explorer (MUSE), pushing such investigations to lower
galaxy masses and higher resolutions. We find that both the MZR and FMR exhibit
different behaviours within different star forming regions of the galaxies. We
find that the SFR surface density - metallicity anti-correlation is tighter in
the low-mass galaxies of our sample. For all the galaxies considered, we find a
SFR surface density - stellar mass surface density correlation. We propose that
the main reason behind these findings is connected to the accretion mechanisms
of the gas fuelling star formation -- low-mass, metal-poor galaxies accrete
pristine gas from the intergalactic medium, while in more massive and
metal-enriched systems the gas responsible for star formation is recycled from
previous star forming episodes.Comment: 15 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
Solar chemical composition in the hot gas of cool-core ellipticals, groups, and clusters of galaxies
The hot intracluster medium (ICM) pervading galaxy clusters and groups is rich in metals, which were synthesised by billions of supernovae and have accumulated in cluster gravitational wells for several Gyrs. Since the products of both Type Ia and core-collapse supernovae - expected to explode over different time scales - are found in the ICM, constraining accurately the chemical composition these hot atmospheres can provide invaluable information on the history of the enrichment of large-scale structures. Recently, Hitomi observations reported solar abundance ratios in the core of the Perseus cluster, in tension with previous XMM-Newton measurements obtained for 44 cool-core clusters, groups, and massive ellipticals (the CHEERS sample). In this work, we revisit the CHEERS results by using an updated version of the spectral code used to fit the data (SPEXACT v3), the same as was used to obtain the Hitomi measurements. Despite limitations in the spectral resolution, the average Cr/Fe and Ni/Fe ratios are now found to be remarkably consistent with unity and in excellent agreement with the Hitomi results. Our updated measurements suggest that the solar composition of the ICM of Perseus is a very common feature in nearby cool-core systems
X-ray spectra of the Fe-L complex
The Hitomi results on the Perseus cluster lead to improvements in our knowledge of atomic physics which are crucial for the precise diagnostic of hot astrophysical plasma observed with high-resolution X-ray spectrometers. However, modeling uncertainties remain, both within but especially beyond Hitomi's spectral window. A major challenge in spectral modeling is the Fe-L spectrum, which is basically a complex assembly of n>2 to n=2 transitions of Fe ions in different ionization states, affected by a range of atomic processes such as collisional excitation, resonant excitation, radiative recombination, dielectronic recombination, and innershell ionization. In this paper we perform a large-scale theoretical calculation on each of the processes with the flexible atomic code (FAC), focusing on ions of Fe XVII to Fe XXIV that form the main body of the Fe-L complex. The new data are found to be consistent within 20% with the recent individual R-matrix calculations for the main Fe-L lines. By further testing the new FAC calculations with the high-quality RGS data from 15 elliptical galaxies and galaxy clusters, we note that the new model gives systematically better fits than the current SPEX v3.04 code, and the mean Fe abundance decreases by 12%, while the O/Fe ratio increases by 16% compared with the results from the current code. Comparing the FAC fit results to those with the R-matrix calculations, we find a temperature-dependent discrepancy of up to ~10% on the Fe abundance between the two theoretical models. Further dedicated tests with both observed spectra and targeted laboratory measurements are needed to resolve the discrepancies, and ultimately, to get the atomic data ready for the next high-resolution X-ray spectroscopy mission
Elemental abundances of the hot atmosphere of luminous infrared galaxy Arp 299
Hot atmospheres of massive galaxies are enriched with metals. Elemental abundances measured in the X-ray band have been used to study the chemical enrichment of supernova remnants, elliptical galaxies, groups, and clusters of galaxies. Here we measure the elemental abundances of the hot atmosphere of luminous infrared galaxy Arp 299 observed with XMM-Newton. To measure the abundances in the hot atmosphere, we use a multi-temperature thermal plasma model, which provides a better fit to the Reflection Grating Spectrometer data. The observed Fe/O abundance ratio is subsolar, while those of Ne/O and Mg/O are slightly above solar. Core-collapse supernovae (SNcc) are the dominant metal factory of elements like O, Ne, and Mg. We find some deviations between the observed abundance patterns and theoretical ones from a simple chemical enrichment model. One possible explanation is that massive stars with M â âȘ 23-27 M oË might not explode as SNcc and enrich the hot atmosphere. This is in accordance with the missing massive SNcc progenitors problem, where very massive progenitors M â âȘ 18 M oË of SNcc have not been clearly detected. It is also possible that theoretical SNcc nucleosynthesis yields of Mg/O yields are underestimated
The NuSTAR and Chandra View of CL 0217+70 and Its Tell-tale Radio Halo
Mergers of galaxy clusters are the most energetic events in the universe, driving shock and cold fronts, generating turbulence, and accelerating particles that create radio halos and relics. The galaxy cluster CL 0217+70 is a remarkable late-stage merger, with a double peripheral radio relic and a giant radio halo. Chandra detects surface brightness (SB) edges that correspond to radio features within the halo. In this work, we present a study of this cluster with Nuclear Spectroscopic Telescope Array and Chandra data using spectro-imaging methods. The global temperature is found to be kT = 9.1 keV. We set an upper limit for the inverse Compton (IC) flux of âŒ2.7 Ă 10 ^â12 erg s ^â1 cm ^â2 , and a lower limit to the magnetic field of 0.08 ÎŒ G. Our local IC search revealed a possibility that IC emission may have a significant contribution at the outskirts of the radio halo emission and on/near shock regions within âŒ0.6 r _500 of clusters. We detected a âhot spotâ feature in our temperature map coincident with an SB edge, but our investigation on its origin is inconclusive. If the âhot spotâ is the downstream of a shock, we set a lower limit of kT > 21 keV to the plasma that corresponds to âŒ2. We found three shock fronts within 0.5 r _500 . Multiple weak shocks within the cluster center hint at an ongoing merger activity and continued feeding of the giant radio halo. CL 0217+70 is the only example hosting these secondary shocks in multiple form
X-ray spectra of the Fe-L complex
The Hitomi results for the Perseus cluster have shown that accurate atomic models are essential to the success of X-ray spectroscopic missions and just as important as the store of knowledge on instrumental calibration and astrophysical modeling. Preparing the models requires a multifaceted approach, including theoretical calculations, laboratory measurements, and calibration using real observations. In a previous paper, we presented a calculation of the electron impact cross sections on the transitions forming the Fe-L complex. In the present work, we systematically tested the calculation against cross-sections of ions measured in an electron beam ion trap experiment. A two-dimensional analysis in the electron beam energies and X-ray photon energies was utilized to disentangle radiative channels following dielectronic recombination, direct electron-impact excitation, and resonant excitation processes in the experimental data. The data calibrated through laboratory measurements were further fed into a global modeling of the Chandra grating spectrum of Capella. We investigated and compared the fit quality, as well as the sensitivity of the derived physical parameters to the underlying atomic data and the astrophysical plasma modeling. We further list the potential areas of disagreement between the observations and the present calculations, which, in turn, calls for renewed efforts with regard to theoretical calculations and targeted laboratory measurements