arXiv subjects

B. I. Ciocan

Publications and source records attributed to B. I. Ciocan.

6 recordsLinked to original sources

arXiv2026

MUSE-DARK III: The evolution of the radial acceleration relation at intermediate redshifts

The radial acceleration relation (RAR) is a tight empirical correlation between the observed radial acceleration (a_tot) and the baryonic radial acceleration (a_bar) measured across galaxy radii: these two accelerations start to deviate significantly from each other below a characteristic acceleration scale, a0. So far, observational studies of the RAR have predominantly focused on galaxies in the local Universe, leaving its evolution with cosmic time largely unexplored. Using high signal-to-noise data from the MUSE Hubble Ultra Deep Field survey, we investigate the RAR with a sample of 79 star-forming galaxies (complete above M* >10^8.8 Msun) at intermediate redshifts (0.33 <z <1.44). We estimate the observed intrinsic acceleration and the baryonic acceleration from a disk-halo decomposition that incorporates stellar, gas, and dark matter components, with corrections for pressure support, using 3D forward modelling. We find a RAR in our intermediate-z sample offset from the local relation, with a higher characteristic acceleration scale, a0(z~1) = 2.38+/-0.1* 10^-10 m/s^2, and a larger intrinsic scatter (~0.17 dex). Dividing the sample into redshift bins and refitting the RAR in each bin, we find a characteristic acceleration scale that systematically increases with z. Parametrizing the z-dependence as a0(z)= a0(0) + a1 * z, we obtain a1 = 1.59+/-0.1 *10^-10 m/s^2, providing evidence for a z-evolution. We find similar results using various dark matter halo profiles as well as the Modified Newtonian Dynamics framework in our 3D forward modelling. Our results show that the RAR persists at intermediate redshift, with statistically significant redshift evolution of the characteristic acceleration, pointing to a possible evolution of the baryon-missing mass connection over cosmic time.

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arXiv2026

MUSE-DARK-I: Dark matter halo properties of intermediate-z star-forming galaxies

[Abridged] We analyse the dark matter (DM) halo properties of 127 0.3 80% of the sample. We find that the kinematically inferred stellar masses agree with values from SED fitting. We find that 89% of galaxies have DM fractions >50%. For 66% of SFGs, we infer a DM inner slope, gamma < 0.5, indicating cored DM profiles, but no correlation is found between gamma and star formation rate of the sample. The stellar- and concentration-mass relations agree with theoretical expectations, but with larger scatter. We confirm the anticorrelation between halo scale radius and DM density. The halo scale radii and DM surface densities increase with Mstar, while DM densities stay constant. We find tentative evidence of an evolution of the DM density with z, which suggests that the DM halos of intermediate-z systems are denser than those of local galaxies. In contrast, the halo scale radii are z-invariant.

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arXiv2024

The MAGPI survey: The interdependence of the mass, star formation rate, and metallicity in galaxies at z~0.3

Star formation rates (SFRs), gas-phase metallicities, and stellar masses are crucial for studying galaxy evolution. The different relations resulting from these properties give insights into the complex interplay of gas inside galaxies and their evolutionary trajectory and current characteristics. We aim to characterize these relations at $z\sim 0.3$, corresponding to a 3-4 Gyr lookback time. We utilized optical integral field spectroscopy of 65 emission-line galaxies from the MAGPI survey at a redshift of $0.28<z<0.35$ and spanning a total stellar mass range of $8.2<\log(M_{*}/M_{\odot}) < 11.4$. We derived the resolved star formation main sequence (rSFMS), resolved mass metallicity relation (rMZR), and resolved fundamental metallicity relation (rFMR) at $z\sim 0.3$. We find a relatively shallow rSFMS slope of $\sim 0.425 \pm 0.014$ compared to the expected slope at this redshift for an ordinary least square (OLS) fitting routine. For an orthogonal distance regression (ODR) routine, a much steeper slope of $\sim 1.162 \pm 0.022$ is measured. We confirm the existence of an rMZR at $z\sim 0.3$ with an average metallicity located $\sim 0.03$ dex above the local Universe's metallicity. Via partial correlation coefficients, evidence is found that the local metallicity is predominantly determined by the stellar mass surface density and has a weak secondary (inverse) dependence on the SFR surface density $Σ_{SFR}$. Additionally, a significant dependence of the local metallicity on the total stellar mass $M_{*}$ is found. Furthermore, we find that the stellar mass surface density $Σ_{*}$ and $M_{*}$ have a significant influence in determining the strength with which $Σ_{SFR}$ correlates with the local metallicity. We observe that at lower stellar masses, there is a tighter correlation between $Σ_{SFR}$ and the gas-phase metallicity, resulting in a more pronounced rFMR.

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arXiv2022

Morpho-kinematics of MACS J0416.1-2403 low mass galaxies

We use optical spectroscopy from VLT/MUSE, as well as photometric observations from HST and VLT/HAWK-I, to study the morpho-kinematics of 17 low mass MACS J0416.1-2403 cluster galaxies at R200 and 5 field galaxies with a redshift of z~0.4. By measuring fluxes of emission lines, we have recovered the star formation rates, gas-phase metallicities and the spatially resolved gas kinematics. We have analysed the structure and morphology of the galaxies from the photometric data, performing a multi-component decomposition into a bulge and a disk. The spatially resolved gas velocity fields were modelled using a 3D approach, which allowed us to retrieve their intrinsic gas kinematics, including the maximum rotation velocity and velocity dispersion. The cluster and field population can be classified as star forming main-sequence galaxies, with only a sub-sample of 4 quenched systems. The lowest mass systems deviate from the predictions of the fundamental metallicity relation, showing higher metallicities, whereas the higher mass ones are in accordance with the model predictions. This might hint at the cut-off of pristine gas inflow and/or the removal of the hot halo gas as the mechanisms driving these offsets. Our morpho-kinematic analysis reveals a sub-sample of dwarfs with maximum velocities vmax <50 km/s, which depart from the Tully-Fisher relation. This might indicate that their interstellar medium is affected by ram pressure stripping. However, ~30% of the cluster galaxies have rotation-dominated gas disks and follow the Tully-Fisher relation. In the stellar mass-S0.5 plane, the systems follow a tight sequence, with only a sub-population of 5 galaxies strongly departing from this relation. Both the morphology and kinematics of the outlier galaxies hint at a combination of pre-processing and cluster-specific interactions affecting their stellar and gas disks.

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arXiv2021

The VLT-MUSE and ALMA view of the MACS 1931.8-2635 brightest cluster galaxy

We reveal the importance of ongoing in-situ star formation in the Brightest Cluster Galaxy in the massive cool-core CLASH cluster MACS 1931.8-2635 at z=0.35. Using a multi-wavelength approach, we assess the stellar and warm ionized medium components, spatially resolved by the VLT-MUSE spectroscopy, and link them to the molecular gas by incorporating sub-mm ALMA observations. We measure the fluxes of strong emission lines, allowing us to determine the physical conditions of the warm ionized gas. The ionized gas flux brightness peak corresponds to the location of the supermassive black hole and the system shows a diffuse warm ionized gas tail extending 30 kpc in N-E direction. The ionized and molecular gas are co-spatial and co-moving, with the gaseous component in the tail falling inward, providing fuel for star formation and accretion-powered nuclear activity. The gas is ionized by a mix of star formation and other energetic processes which give rise to LINER-like emission, with active galactic nuclei emission dominant only in the BCG core. We measure a star formation rate of 97 Msun/yr, with its peak at the BCG core. However, star formation accounts for only 50-60% of the energetics needed to ionize the warm gas. In situ star formation generated by thermally unstable intracluster medium cooling and/or dry mergers dominate the stellar mass growth at z<0.5 and these mechanisms account for the build-up of 20% of the mass of the system. Our measurements reveal that the most central regions of the BCG contain the lowest gas phase oxygen abundance, whereas the tail exhibits slightly more elevated values. The galaxy is a dispersion dominated system, typical for massive, elliptical galaxies. The gas and stellar kinematics are decoupled, with the gaseous velocity fields being more closely related to the bulk motions of the intracluster medium.

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arXiv2019

CLASH-VLT: Enhancement of (O/H) in z=0.35 RXJ 2248-4431 cluster galaxies

(Abridged) We explore the Frontier Fields cluster RXJ2248-443 at z~0.35 with VIMOS/VLT spectroscopy from CLASH-VLT, which covers a central region corresponding to almost 2 virial radii. The fluxes of [OII], Hbeta, [OIII], Halpha and [NII] emission lines were measured allowing the derivation of (O/H) gas metallicities, star formation rates based on extinction-corrected Halpha fluxes and active galactic nuclei (AGN) contamination. We compare our sample of cluster galaxies to a population of field galaxies at similar redshifts. We use the location of galaxies in projected phase-space to distinguish between cluster and field galaxies. Both populations follow the star-forming-sequence in the diagnostic diagrams, which allow disentangling between the ionising sources in a galaxy, with only few galaxies classified as Seyfert II. Both field and cluster galaxies follow the "Main-Sequence" of star forming galaxies, with no substantial difference observed between the two populations. In the Mass - Metallicity (MZ) plane, both high mass field and cluster galaxies show comparable (O/H)s to the local SDSS MZ relation, with an offset of low mass galaxies towards higher metallicities. While both the metallicities of "accreted" (R < R500) and "infalling" (R > R500) cluster members are comparable at all masses, the cluster galaxies from the intermediate, mass complete bin show more enhanced metallicities than their field counterparts. The intermediate mass field galaxies are in accordance with the expected (O/H)s from the Fundamental Metallicity relation, while the cluster members deviate strongly from the model predictions. The results of this work are in accordance with studies of other clusters at z < 0.5 and favour the scenario in which the hot halo gas of log(M/Msun)<10.2 cluster galaxies is removed due to mild ram pressure stripping, leading to an increase in their gas-phase metallicity.

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