Neutral Mo6Q8-clusters with terminal phosphane ligands – a route to water soluble molecular units of Chevrel phases

Despite the numerous works on Chevrel phases, their building blocks – molecular compounds containing {Mo6Q8} cluster core, are hardly presented in literature. Here we present rare examples of phosphane molybdenum...

What’s Behind the Elephant’s Trunk? Identifying Young Stellar Objects on the Outskirts of IC 1396*

Empirically, the estimated lifetime of a typical protoplanetary disk is <5–10 Myr. However, the disk lifetimes required to produce a variety of observed exoplanetary systems may exceed this timescale. Some hypothesize that this inconsistency is due to estimating disk fractions at the cores of clusters, where radiation fields external to a star–disk system can photoevaporate the disk. To test this, we have observed a field on the western outskirts of the IC 1396 star-forming region with XMM-Newton to identify new Class III YSO cluster members. Our X-ray sample is complete for YSOs down to 1.8 M ⊙. We use a subset of these X-ray sources that have near- and mid-infrared counterparts to determine the disk fraction for this field. We find that the fraction of X-ray-detected cluster members that host disks in the field we observe is 17 − 7 + 10 % (1σ), comparable with the 29 − 3 + 4 % found in an adjacent field centered on the cometary globule IC 1396A. We reevaluate YSO identifications in the IC 1396A field using Gaia parallaxes compared to previous color-cut-only identifications, finding that incorporating independent distance measurements provides key additional constraints. Given the existence of at least one massive star producing an external radiation field in the cluster core, the lack of a statistically significant difference in disk fraction in each observed field suggests that disk lifetimes remain consistent as a function of distance from the cluster core.

Hexaaquadodeca-μ2-iodido-octahedro-hexatantalum diiodide tetrahydrate

In the crystal structure of the cluster salt, [Ta6I12(H2O)6]I2·4H2O, the octahedral {Ta6} cluster core is μ2-coordinated by twelve iodido ligands (inner ligand sphere) whereas the six aqua ligands coordinate each at the six outer positions. The discrete, inversion-symmetric cluster complex is double-positively charged, and two iodide anions are present in the crystal structure as counter-ions. In addition, four water molecules are co-crystallized. Hydrogen bonds between the cluster unit, the iodide anions and co-crystallized water molecules stabilize the charge-assisted packing in the crystal structure.

Optical and near-infrared observations of the SPT2349-56 proto-cluster core at z = 4.3

ABSTRACT We present Gemini-S and Spitzer-IRAC optical-through-near-IR observations in the field of the SPT2349-56 proto-cluster at z = 4.3. We detect optical/IR counterparts for only 9 of the 14 submillimetre galaxies (SMGs) previously identified by ALMA in the core of SPT2349-56. In addition, we detect four z ∼ 4 Lyman-break galaxies (LBGs) in the 30 arcsec-diameter region surrounding this proto-cluster core. Three of the four LBGs are new systems, while one appears to be a counterpart of one of the nine observed SMGs. We identify a candidate brightest cluster galaxy (BCG) with a stellar mass of $(3.2^{+2.3}_{-1.4})\times 10^{11}$ M⊙. The stellar masses of the eight other SMGs place them on, above, and below the main sequence of star formation at z ≈ 4.5. The cumulative stellar mass for the SPT2349-56 core is at least (12.2 ± 2.8) × 1011 M⊙, a sizeable fraction of the stellar mass in local BCGs, and close to the universal baryon fraction (0.19) relative to the virial mass of the core (1013 M⊙). As all 14 of these SMGs are destined to quickly merge, we conclude that the proto-cluster core has already developed a significant stellar mass at this early stage, comparable to z = 1 BCGs. Importantly, we also find that the SPT2349-56 core structure would be difficult to uncover in optical surveys, with none of the ALMA sources being easily identifiable or constrained through g, r, and i colour selection in deep optical surveys and only a modest overdensity of LBGs over the more extended structure. SPT2349-56 therefore represents a truly dust-obscured phase of a massive cluster core under formation.

Massive molecular gas reservoir around the central AGN in the CARLA J1103 + 3449 cluster at z = 1.44

Passive early-type galaxies dominate cluster cores at z ≲ 1.5. At higher redshift, cluster core galaxies are observed to have on-going star-formation, which is fueled by cold molecular gas. We measured the molecular gas reservoir of the central region around the radio-loud active galactic nucleus (AGN) in the cluster CARLA J1103 + 3449 at z = 1.44 using NOEMA. The AGN synchrotron emission dominates the continuum emission at 94.48 GHz, and we measured its flux at the AGN position and at the position of two radio jets. Combining our measurements with published results over the range 4.71–94.5 GHz, and assuming Ssynch ∝ ν−α, we obtain a flat spectral index of α = 0.14 ± 0.03 for the AGN core emission, and a steeper index of α = 1.43 ± 0.04 and α = 1.15 ± 0.04 at positions close to the western and eastern lobes, respectively. The total spectral index is α = 0.92 ± 0.02 over the range 73.8 MHz–94.5 GHz. We detect two CO(2–1) emission lines, both blueshifted with respect to the AGN. Their emission corresponds to two regions, ~17 kpc southeast and ~14 kpc southwest of the AGN, not associated with galaxies. In these two regions, we find a total massive molecular gas reservoir of Mgastot = 3.9 ± 0.4 × 1010 M⊙, which dominates (≳60%) the central total molecular gas reservoir. These results can be explained by massive cool gas flows in the center of the cluster. The AGN early-type host is not yet quenched; its star formation rate is consistent with being on the main sequence of star-forming galaxies in the field (star formation rate ~30–140 M⊙ yr−1), and the cluster core molecular gas reservoir is expected to feed the AGN and the host star formation before quiescence. The other confirmed cluster members show star formation rates at ~2σ below the field main sequence at similar redshifts and do not have molecular gas masses larger than galaxies of similar stellar mass in the field.

The Fornax Deep Survey with VST

Context. We present the study of the south-west group in the Fornax cluster centred on the brightest group galaxy (BGG) Fornax A, which was observed as part of the Fornax Deep Survey (FDS). This includes the analysis of the bright group members (mB < 16 mag) and the intra-group light (IGL). Aims. The main objective of this work is to investigate the assembly history of the Fornax A group and to compare its physical quantities as a function of the environment to that of the Fornax cluster core. Methods. For all galaxies, we extracted the azimuthally averaged surface brightness profiles in three optical bands (g, r, i) by modelling the galaxy’s isophotes. We derived their colour (g − i) profiles, total magnitude, effective radius in all respective bands, stellar mass, and the break radius in the r-band. The long integration time and large covered area of the FDS allowed us to also estimate the amount of IGL. Results. The majority of galaxies in the Fornax A group are late-type galaxies (LTGs), spanning a range of stellar mass of 8 < log(M* M⊙) < 10.5. Six out of nine LTGs show a Type III (up-bending) break in their light profiles, which is either suggestive of strangulation halting star formation in their outskirts or their H I-richness causing enhanced star formation in their outer-discs. Overall, we do not find any correlations between their physical properties and their group-centric distance. The estimated luminosity of the IGL is 6 ± 2 × 1010 L⊙ in the g-band, which corresponds to about 16% of the total light in the group. Conclusions. The Fornax A group appears to be in an early-stage of assembly with respect to the cluster core. The environment of the Fornax A group is not as dense as that of the cluster core, with all galaxies except the BGG showing similar morphology, comparable colours and stellar masses, and Type III disc-breaks, without any clear trend in these properties with group-centric distances. The low amount of IGL is also consistent with this picture, since there were no significant gravitational interactions between galaxies that modified the galaxies’ structure and contributed to the build-up of the IGL. The main contribution to the IGL is from the minor merging in the outskirts of the BGG NGC 1316 and, probably, the disrupted dwarf galaxies close to the group centre.