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Register a new userThe evolution of the spatially-resolved metal abundance in galaxy clusters up to z=1.4
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We present the combined analysis of the metal content of 83 objects in the redshift range 0.09-1.39, and spatially-resolved in the 3 bins (0-0.15, 0.15-0.4, >0.4) R500, as obtained with similar analysis using XMM-Newton data in Leccardi & Molendi (2008) and Baldi et al. (2012). We use the pseudo-entropy ratio to separate the Cool-Core (CC) cluster population, where the central gas density tends to be relatively higher, cooler and more metal rich, from the Non-Cool-Core systems. The average, redshift-independent, metal abundance measured in the 3 radial bins decrease moving outwards, with a mean metallicity in the core that is even 3 (two) times higher than the value of 0.16 times the solar abundance in Anders & Grevesse (1989) estimated at r>0.4 R500 in CC (NCC) objects. We find that the values of the emission-weighted metallicity are well-fitted by the relation $Z(z) = Z_0 (1+z)^{-gamma}$ at given radius. A significant scatter, intrinsic to the observed distribution and of the order of 0.05-0.15, is observed below 0.4 R500. The nominal best-fit value of $gamma$ is significantly different from zero in the inner cluster regions ($gamma = 1.6 pm 0.2$) and in CC clusters only. These results are confirmed also with a bootstrap analysis, which provides a still significant negative evolution in the core of CC systems (P>99.9 per cent). No redshift-evolution is observed when regions above the core (r > 0.15 R500) are considered. A reasonable good fit of both the radial and redshift dependence is provided from the functional form $Z(r,z)=Z_0 (1+(r/0.15 R500)^2)^{-beta} (1+z)^{-gamma}$, with $(Z_0, beta, gamma) = (0.83 pm 0.13, 0.55 pm 0.07, 1.7 pm 0.6)$ in CC clusters and $(0.39 pm 0.04, 0.37 pm 0.15, 0.5 pm 0.5)$ for NCC systems. Our results represent the most extensive study of the spatially-resolved metal distribution in the cluster plasma as function of redshift.
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We carry out a systematic study of the recently discovered fundamental plane of galaxy clusters (CFP) using a sample of ~250 simulated clusters from the 300th project, focusing on the stability of the plane against different temperature definitions and its dependence on the dynamical relaxation state of clusters. The CFP is characterised in the form of $T propto M_s^alpha r_s^beta$, defined with the gas temperature ($T$) and the characteristic halo scale radius and mass ($r_s$ and $M_s$) assuming an NFW halo description. We explore two definitions of weighted temperatures, namely mass-weighted and spectroscopic-like temperatures, in three radial ranges: [0.1, 1.0]$r_{200}$, [0.15,1.0]$r_{500}$, and [50,500]$h^{-1}$ kpc. We find that 300th clusters at $z=0$ lie on a thin plane whose parameters ($alpha, beta$) and dispersion (0.015--0.030 dex) depend on the gas temperature definition. The CFP for mass-weighted temperatures is closer to the virial equilibrium expectation ($alpha=1, beta=-1$) with a smaller dispersion. When gas temperatures are measured inside 500$h^{-1}$ kpc, which is close to the median value of $r_s$, the resulting CFP deviates the most from the virial expectation and shifts towards the similarity solution for a secondary infall model ($alpha=1.5, beta=-2$). Independently of the temperature definition, we find that clusters at $z=1$ form a CFP similar to the virial expectation. At all epochs, the CFP remains well defined throughout the evolution of the cluster population. The CFP of relaxed clusters is always close to the virial expectation, with a milder evolution than for the unrelaxed case. We find that only systems formed over the last 4 Gyr have a CFP that is closer to the self-similar solution. All these findings are compatible with the CFP obtained for a CLASH subsample excluding the hottest clusters with $T_X>12$ keV.
We analyzed the luminosity-temperature-mass of gas (L_{X} - T - M_{g}) relation for sample of galaxy clusters that have been observed by the Chandra satellite. We used 21 high-redshift clusters (0.4 < z < 1.4). We assumed a power-law relation between the X-ray luminosity of galaxy clusters and its temperature and redshift L_{X} ~ (1+z)^{A_{L_{X}T}}T^{beta_{L_{X}T}}. We obtained that for an Omega_{m} = 0.27 and Lambda = 0.73 universe, A_{L_{X}T} = 1.50 +/- 0.23, beta_{L_{X}T} = 2.55 +/- 0.07 (for 68% confidence level). Then, we found the evolution of M_{g} - T relation is small. We assumed a power-law relation in the form M_{g} ~ (1+z)^{A_{M_{g}T}}T^{beta_{M_{g}T}} also, and we obtained A_{M_{g}T} = -0.58 +/- 0.13 and beta_{M_{g}T} = 1.77 +/- 0.16. We also obtained the evolution in M_{g} - L_{X} relation, we can conclude that such relation has strong evolution for our cosmological parameters. We used M_{g} ~ (1+z)^{A_{M_{g}L_{X}}}L^{beta_{M_{g}L_{X}}} equation for assuming this relation and we found A_{M_{g}L_{X}} ~ -1.86 +/- 0.34 and beta_{M_{g}L_{X}} = 0.73 +/- 0.15 for Omega_{m} = 0.27 and Lambda = 0.73 universe. In overal, the clusters on big redshifts have much stronger evolution between correlations of luminosity, temperature and mass, then such correlations for clusters at small redshifts. We can conclude that such strong evolution in L_{X} - T - M_{g} correlations indicate that in the past the clusters have bigger temperature and higher luminosity.
We derive average radial gradients in the dust attenuation towards HII regions in 609 galaxies at z~1.4, using measurements of the Balmer decrement out to r~3kpc. The Balmer decrements are derived from spatially resolved maps of Halpha and Hbeta emission from the 3D-HST survey. We find that with increasing stellar mass (M) both the normalization and strength of the gradient in dust attenuation increases. Galaxies with a mean mass of <log(M)> = 9.2Msun have little dust attenuation at all radii, whereas galaxies with <log(M)>= 10.2Msun have dust attenuation toward Halpha A(Halpha)~2mag in their central regions. We parameterize this as A(Halpha) = b + c log(r), with b = 0.9 + 1.0 log(M10), c = -1.9 - 2.2 log(M10), r in kpc, and M10 the stellar mass in units of 10^10Msun. This expression can be used to correct spatially resolved measurements of Halpha to radial distributions of star formation. When applied to our data, we find that the star formation rates in the central r<1kpc of galaxies in the highest mass bin are ~ 6 Msun/yr, six times higher than before correction and approximately half of the total star formation rate of these galaxies. If this high central star formation rate is maintained for several Gyr, a large fraction of the stars in present-day bulges likely formed in-situ.
Determining the AGN content in structures of different mass/velocity dispersion and comparing them to higher mass/lower redshift analogs is important to understand how the AGN formation process is related to environmental properties. We use our well-tested cluster finding algorithm to identify structures in the GOODS North and South fields, exploiting the available spectroscopic redshifts and accurate photometric redshifts. We identify 9 structures in GOODS-south (presented in a previous paper) and 8 new structures in GOODS-north. We only consider structures where at least 2/3 of the members brighter than M_R=-20 have a spectroscopic redshift. For those group members that coincide with X-ray sources in the 4 and 2 Msec Chandra source catalogs respectively, we determine if the X-ray emission originates from AGN activity or it is related to the galaxies star-formation activity. We find that the fraction of AGN with Log L_H > 42 erg/s in galaxies with M_R < -20 is on average 6.3+-1.3%, much higher than in lower redshift groups of similar mass and more than double the fraction found in massive clusters at a similarly high redshift. We then explore the spatial distribution of AGN in the structures and find that they preferentially populate the outer regions. The colors of AGN host galaxies in structures tend to be confined to the green valley, thus avoiding the blue cloud and, partially, also the red-sequence, contrary to what happens in the field. We finally compare our results to the predictions of two sets of semi analytic models to investigate the evolution of AGN and evaluate potential triggering and fueling mechanisms. The outcome of this comparison attests the importance of galaxy encounters, not necessarily leading to mergers, as an efficient AGN triggering mechanism. (abridged)
We present the first results from a study of OVI absorption around galaxies at $z<1.44$ using data from a near-infrared grism spectroscopic Hubble Space Telescope Large Program, the Quasar Sightline and Galaxy Evolution (QSAGE) survey. QSAGE is the first grism galaxy survey to focus on the circumgalactic medium at $zsim1$, providing a blind survey of the galaxy population. Using the first of 12 fields, we provide details of the reduction methods, in particular the handling of the deep grism data which uses multiple position angles to minimise the effects of contamination from overlapping traces. The resulting galaxy sample is H$alpha$ flux limited ($f({rm Halpha}) > 2times10^{-17}$ erg s$^{-1}$ cm$^{-2}$) at 0.68<z<1.44, corresponding to $gtrsim0.2-0.8$ M$_odot$ yr$^{-1}$. We combine the galaxy data with high-resolution STIS and COS spectroscopy of the background quasar to study OVI in the circumgalactic medium. At z>0.68, we find 5 OVI absorption systems along the line of sight with identified galaxies lying at impact parameters of $bapprox100-350$ kpc (proper), whilst we find a further 13 galaxies with no significant associated OVI absorption (i.e. $N({rm OVI})<10^{13.5-14}$ cm$^{-2}$) in the same impact parameter and redshift range. We find a large scatter in the stellar mass and star-formation rates of the closest galaxies with associated OVI. Whilst one of the OVI absorber systems is found to be associated with a low mass galaxy group at $zapprox1.08$, we infer that the detected OVI absorbers typically lie in the proximity of dark matter halos of masses $10^{11.5} {rm M_odot}lesssim M_{rm halo}lesssim10^{12} {rm M_odot}$.
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