COMAP Early Science. I. Overview Cleary, Kieran A.; Borowska, Jowita; Breysse, Patrick C. ...
Astrophysical journal/The Astrophysical journal,
07/2022, Letnik:
933, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
The CO Mapping Array Project (COMAP) aims to use line-intensity mapping of carbon monoxide (CO) to trace the distribution and global properties of galaxies over cosmic time, back to the ...Epoch of Reionization (EoR). To validate the technologies and techniques needed for this goal, a Pathfinder instrument has been constructed and fielded. Sensitive to CO(1–0) emission from
z
= 2.4–3.4 and a fainter contribution from CO(2–1) at
z
= 6–8, the Pathfinder is surveying 12 deg
2
in a 5 yr observing campaign to detect the CO signal from
z
∼ 3. Using data from the first 13 months of observing, we estimate
P
CO
(
k
) = −2.7 ± 1.7 × 10
4
μ
K
2
Mpc
3
on scales
k
= 0.051 −0.62 Mpc
−1
, the first direct three-dimensional constraint on the clustering component of the CO(1–0) power spectrum. Based on these observations alone, we obtain a constraint on the amplitude of the clustering component (the squared mean CO line temperature bias product) of
Tb
2
<
49
μ
K
2
, nearly an order-of-magnitude improvement on the previous best measurement. These constraints allow us to rule out two models from the literature. We forecast a detection of the power spectrum after 5 yr with signal-to-noise ratio (S/N) 9–17. Cross-correlation with an overlapping galaxy survey will yield a detection of the CO–galaxy power spectrum with S/N of 19. We are also conducting a 30 GHz survey of the Galactic plane and present a preliminary map. Looking to the future of COMAP, we examine the prospects for future phases of the experiment to detect and characterize the CO signal from the EoR.
Three new arsenato-polyoxovanadates with the composition M(en)32V6As8O26 (M = Co2+ (I), Zn2+ (II), and Cd2+ (III)) were synthesized under solvothermal conditions in high yields, thus significantly ...enhancing the knowledge of As-rich polyoxovanadate cluster chemistry. The compounds are isostructural and feature the very rare V6IVAs8IIIO264− cluster anion. The cluster shell is constructed by interconnection of two trimeric {V3O11} groups consisting of three edge-sharing VO5 polyhedra and four As2O5 units, which are formed by two corner-sharing AsO3 pyramids. While the As2O5 group is a common structural feature in arsenato-polyoxovanadates, the {V3O11} unit is only observed in V-rich high-nuclear heteroatom-containing polyoxovanadates {V14E8} (E = As, Sb, Ge). The complexes adopt the Λ (δδδ) conformation, which is the most stable arrangement. Interestingly, the unit cell parameters do not scale with the volume of the M(en)32+ complexes, assuming a constant volume of the anion. Only a very detailed Hirshfeld surface analysis revealed that the van der Waals volume of the {V6As8O26} moiety is the smallest for the Cd-containing compound, while the volumes of the anions in the other two compounds are very similar. Therefore, the observed trends of the lattice parameters can be explained on the basis of these findings. Furthermore, intermolecular interactions include As⋯H contacts in addition to O⋯H and H⋯H interactions. The electronic spectrum of I contains d–d transitions of the vanadyl group and of the Co2+ cation. As expected only the d–d transitions of the VO2+ unit occur for II and III.
COMAP Early Science. II. Pathfinder Instrument Lamb, James W.; Cleary, Kieran A.; Woody, David P. ...
Astrophysical journal/The Astrophysical journal,
07/2022, Letnik:
933, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Line intensity mapping (LIM) is a new technique for tracing the global properties of galaxies over cosmic time. Detection of the very faint signals from redshifted carbon monoxide (CO), a ...tracer of star formation, pushes the limits of what is feasible with a total-power instrument. The CO Mapping Project Pathfinder is a first-generation instrument aiming to prove the concept and develop the technology for future experiments, as well as delivering early science products. With 19 receiver channels in a hexagonal focal plane arrangement on a 10.4 m antenna and an instantaneous 26–34 GHz frequency range with 2 MHz resolution, it is ideally suited to measuring CO (
J
= 1–0) from
z
∼ 3. In this paper we discuss strategies for designing and building the Pathfinder and the challenges that were encountered. The design of the instrument prioritized LIM requirements over those of ancillary science. After a couple of years of operation, the instrument is well understood, and the first year of data is already yielding useful science results. Experience with this Pathfinder will guide the design of the next generations of experiments.
Minimal-nuclearity vanadato-tungstate clusters in {V(IV)(dien)}4WO14·4H2O () and {V(IV)(dien)}4WO20·6H2O () feature cores of edge-sharing WO6 octahedra, surrounded by a ring of four vanadyl groups. ...Surprisingly, the V(iv) centers in both and are ferromagnetically coupled, in contrast to all other known vanadato-polyoxotungstates featuring the ubiquituos V-O-W-O-V exchange pathways.
A new arsenato-polyoxovanadate with the composition {Ni(dien)
V
As
}
·2 Cl
has been crystallized under solvothermal conditions as turquoise block-like crystals. The central structural feature is the ...V
As
cluster anion, which is composed of two trinuclear {V
} groups consisting of three edge-sharing VO
polyhedra. Pairs of pyramidal AsO
moieties share a common corner forming As
units, which interconnect the {V
} groups. One of the Ni(dien)
complexes adopts the
(Ni1) and the second complex the
configuration (Ni2). The Cl
anion is involved in strong hydrogen bonding interactions and links the Ni(dien)
complexes to form twelve-membered rings which host the V
As
cluster anions. The Hirshfeld surface analysis yields a detailed picture of the intermolecular interactions revealing clear differences for the two unique Ni(dien)
complexes. Intermolecular contacts also include As⋯H, O⋯H and H⋯H interactions. In the electronic spectrum the bands of
transitions of the vanadyl group and of the Ni
cations overlap, preventing a detailed analysis.
The new coordination polymer Cr(en)2As2VO7 (en=ethylenediamine) was synthesized under solvothermal conditions as deep red crystals. In the crystal structure VO4 tetrahedra and As2O5 handles formed by ...corner‐sharing of two AsO3 pyramidal units are joined by common oxygen atoms into an undulated chain that is directed along the crystallographic b‐axis. The chain is decorated by Cr(en)23+ complexes with the Cr3+ cation having bonds to two terminal O2− anions of the As2O5 moiety thus generating a CrN4O2 octahedron, which displays a cis‐configuration. The connection mode between Cr3+ and As2O5 leads to formation of a six‐membered CrAs2O3 ring. The chains are arranged in a layer‐like fashion in the (001) plane and these layers are stacked along 001. A large number of N−H⋅⋅⋅O and C−H⋅⋅⋅O hydrogen bonds generate a three dimensional network. A Hirshfeld surface analysis was performed for visualizing the extended interchain interactions. The hydrogen bonding interactions are clearly detected in the IR spectrum. The UV‐Vis spectrum shows an absorption at 2.3 eV which is in agreement with the red color of the sample.
Abstract
The new coordination polymer Cr(en)
2
As
2
VO
7
(en=ethylenediamine) was synthesized under solvothermal conditions as deep red crystals. In the crystal structure VO
4
tetrahedra and As
2
O
5
...handles formed by corner‐sharing of two AsO
3
pyramidal units are joined by common oxygen atoms into an undulated chain that is directed along the crystallographic b‐axis. The chain is decorated by Cr(en)
2
3+
complexes with the Cr
3+
cation having bonds to two terminal O
2−
anions of the As
2
O
5
moiety thus generating a CrN
4
O
2
octahedron, which displays a cis‐configuration. The connection mode between Cr
3+
and As
2
O
5
leads to formation of a six‐membered CrAs
2
O
3
ring. The chains are arranged in a layer‐like fashion in the (001) plane and these layers are stacked along 001. A large number of N−H⋅⋅⋅O and C−H⋅⋅⋅O hydrogen bonds generate a three dimensional network. A Hirshfeld surface analysis was performed for visualizing the extended interchain interactions. The hydrogen bonding interactions are clearly detected in the IR spectrum. The UV‐Vis spectrum shows an absorption at 2.3 eV which is in agreement with the red color of the sample.
Three new arsenato-polyoxovanadates with the composition M(en)sub.3sub.2Vsub.6Assub.8Osub.26 (M = Cosup.2+ (I), Znsup.2+ (II), and Cdsup.2+ (III)) were synthesized under solvothermal conditions in ...high yields, thus significantly enhancing the knowledge of As-rich polyoxovanadate cluster chemistry. The compounds are isostructural and feature the very rare Vsub.6 sup.IVAssub.8 sup.IIIOsub.26sup.4− cluster anion. The cluster shell is constructed by interconnection of two trimeric {Vsub.3Osub.11} groups consisting of three edge-sharing VOsub.5 polyhedra and four Assub.2Osub.5 units, which are formed by two corner-sharing AsOsub.3 pyramids. While the Assub.2Osub.5 group is a common structural feature in arsenato-polyoxovanadates, the {Vsub.3Osub.11} unit is only observed in V-rich high-nuclear heteroatom-containing polyoxovanadates {Vsub.14Esub.8} (E = As, Sb, Ge). The complexes adopt the Λ (δδδ) conformation, which is the most stable arrangement. Interestingly, the unit cell parameters do not scale with the volume of the M(en)sub.3sup.2+ complexes, assuming a constant volume of the anion. Only a very detailed Hirshfeld surface analysis revealed that the van der Waals volume of the {Vsub.6Assub.8Osub.26} moiety is the smallest for the Cd-containing compound, while the volumes of the anions in the other two compounds are very similar. Therefore, the observed trends of the lattice parameters can be explained on the basis of these findings. Furthermore, intermolecular interactions include As⋯H contacts in addition to O⋯H and H⋯H interactions. The electronic spectrum of I contains d–d transitions of the vanadyl group and of the Cosup.2+ cation. As expected only the d–d transitions of the VOsup.2+ unit occur for II and III.
Abstract
Solvothermal exploration of the As, V, Mn reaction system in the presence of aqueous diethylenetriamine (=dien) solution led to the discovery of Mn
II
4
V
IV
12
As
III
8
O
40
(dien)
4
(H
2
...O) ⋅ 3.5H
2
O, containing the first arsenato‐polyoxovanadate featuring a {Mn
2
V
12
As
8
O
40
} cluster shell. In comparison to its parental {V
14
As
8
O
42
} archetype, two vanadyl (VO
2+
) units at opposite ends of the polyoxovanadate shell here are substituted by Mn
2+
centers. In the solid state, these {Mn
2
V
12
As
8
O
40
} units are joined into rods by sharing common Mn−O−V linkages. Expansion of the cluster shell by two further Mn
2+
sites via Mn−O=V bridges generates a {Mn
4
V
12
As
8
O
40
} moiety. Three Mn
2+
cations are joined by monodentate‐coordinating dien ligands, which link the rods into layers. The dien ligands here coexist in three different coordination modes: monodentate, bidentate and tridentate, which is rarely observed. Magnetic susceptibility measurements show the expected significant antiferromagnetic coupling interactions between all spin centers present in the title compound, namely the isotropic spin‐5/2 Mn
2+
centers and the isotropic spin‐1/2 vanadyl groups, in line with most other heterometal‐substituted arsenato‐polyoxovanadate(IV) clusters.
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