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We present the current state of models for the $z\sim3$ carbon monoxide (CO) line-intensity signal targeted by the CO Mapping Array Project (COMAP) Pathfinder in the context of its early science results. Our fiducial model, relating dark matter halo properties to CO luminosities, informs parameter priors with empirical models of the galaxy-halo connection and previous CO(1-0) observations. The Pathfinder early science data spanning wavenumbers $k=0.051$-$0.62\,$Mpc$^{-1}$ represent the first direct 3D constraint on the clustering component of the CO(1-0) power spectrum. Our 95% upper limit on the redshift-space clustering amplitude $A_{\rm clust}\lesssim70\,\mu$K$^2$ greatly improves on the indirect upper limit of $420\,\mu$K$^2$ reported from the CO Power Spectrum Survey (COPSS) measurement at $k\sim1\,$Mpc$^{-1}$. The COMAP limit excludes a subset of models from previous literature, and constrains interpretation of the COPSS results, demonstrating the complementary nature of COMAP and interferometric CO surveys. Using line bias expectations from our priors, we also constrain the squared mean line intensity-bias product, $\langle{Tb}\rangle^2\lesssim50\,\mu$K$^2$, and the cosmic molecular gas density, $\rho_\text{H2}, Comment: Paper 5 of 7 in series. 17 pages + appendix and bibliography (30 pages total); 15 figures, 6 tables; accepted for publication in ApJ; v3 reflects the accepted version with minor changes and additions to text

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)2]3+ 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.

We introduce COMAP-EoR, the next generation of the Carbon Monoxide Mapping Array Project aimed at extending CO intensity mapping to the Epoch of Reionization. COMAP-EoR supplements the existing 30 GHz COMAP Pathfinder with two additional 30 GHz instruments and a new 16 GHz receiver. This combination of frequencies will be able to simultaneously map CO(1--0) and CO(2--1) at reionization redshifts ($z\sim5-8$) in addition to providing a significant boost to the $z\sim3$ sensitivity of the Pathfinder. We examine a set of existing models of the EoR CO signal, and find power spectra spanning several orders of magnitude, highlighting our extreme ignorance about this period of cosmic history and the value of the COMAP-EoR measurement. We carry out the most detailed forecast to date of an intensity mapping cross-correlation, and find that five out of the six models we consider yield signal to noise ratios (S/N) $\gtrsim20$ for COMAP-EoR, with the brightest reaching a S/N above 400. We show that, for these models, COMAP-EoR can make a detailed measurement of the cosmic molecular gas history from $z\sim2-8$, as well as probe the population of faint, star-forming galaxies predicted by these models to be undetectable by traditional surveys. We show that, for the single model that does not predict numerous faint emitters, a COMAP-EoR-type measurement is required to rule out their existence. We briefly explore prospects for a third-generation Expanded Reionization Array (COMAP-ERA) capable of detecting the faintest models and characterizing the brightest signals in extreme detail., Comment: Paper 7 of 7 in series. 19 pages, 10 figures, to be submitted to ApJ

We present early results from the COMAP Galactic Plane Survey conducted between June 2019 and April 2021, spanning $20^\circ, Paper 6 of 7 in series. 28 pages, 10 figures, submitted to ApJ

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-year observing campaign to detect the CO signal from $z\sim3$. Using data from the first 13 months of observing, we estimate $P_\mathrm{CO}(k) = -2.7 \pm 1.7 \times 10^4\mu\mathrm{K}^2 \mathrm{Mpc}^3$ on scales $k=0.051-0.62 \mathrm{Mpc}^{-1}$ - the first direct 3D 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 $\langle Tb\rangle^2, Comment: Paper 1 of 7 in series. 18 pages, 16 figures, submitted to ApJ

We present the power spectrum methodology used for the first-season COMAP analysis, and assess the quality of the current data set. The main results are derived through the Feed-feed Pseudo-Cross-Spectrum (FPXS) method, which is a robust estimator with respect to both noise modeling errors and experimental systematics. We use effective transfer functions to take into account the effects of instrumental beam smoothing and various filter operations applied during the low-level data processing. The power spectra estimated in this way have allowed us to identify a systematic error associated with one of our two scanning strategies, believed to be due to residual ground or atmospheric contamination. We omit these data from our analysis and no longer use this scanning technique for observations. We present the power spectra from our first season of observing and demonstrate that the uncertainties are integrating as expected for uncorrelated noise, with any residual systematics suppressed to a level below the noise. Using the FPXS method, and combining data on scales $k=0.051-0.62 \,\mathrm{Mpc}^{-1}$ we estimate $P_\mathrm{CO}(k) = -2.7 \pm 1.7 \times 10^4\mu\textrm{K}^2\mathrm{Mpc}^3$, the first direct 3D constraint on the clustering component of the CO(1-0) power spectrum in the literature., Comment: Paper 4 of 7 in series. 18 pages, 11 figures, as accepted in ApJ

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 (COMAP) 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 $z\sim3$. 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 drive the design of the next generations of experiments., Comment: Paper 2 of 7 in series. 27 pages, 28 figures, submitted to ApJ

We describe the first season COMAP analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain calibration, filtering, data selection, and map-making. Absolute gain calibration relies on a combination of instrumental and astrophysical sources, while relative gain calibration exploits real-time total-power variations. High efficiency filtering is achieved through spectroscopic common-mode rejection within and across receivers, resulting in nearly uncorrelated white noise within single-frequency channels. Consequently, near-optimal but biased maps are produced by binning the filtered time stream into pixelized maps; the corresponding signal bias transfer function is estimated through simulations. Data selection is performed automatically through a series of goodness-of-fit statistics, including $\chi^2$ and multi-scale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a dataset with very low levels of correlated noise. We find that one of our two scanning strategies (the Lissajous type) is sensitive to residual instrumental systematics. As a result, we no longer use this type of scan and exclude data taken this way from our Season 1 power spectrum estimates. We perform a careful analysis of our data processing and observing efficiencies and take account of planned improvements to estimate our future performance. Power spectrum results derived from the first-season COMAP maps are presented and discussed in companion papers., Comment: Paper 3 of 7 in series. 26 pages, 23 figures, submitted to ApJ

The new compound {[Mn(teta)]4V16Sb4O42}n·[(H2O)12]n (1) was synthesized under solvothermal conditions. The crystal structure features the high nuclearity [V16IVSb4IIIO42(H2O)]8– cluster anion, which consists of two rings composed of 8 edge-sharing VO5 polyhedra. The rings are perpendicular to each other generating four niches, which are occupied by two VO5 pyramids and two handle-like Sb2O5 units. The two unique anions are each surrounded by eight Mn2+ centered complexes via Mn–Oterm–V bonds. Such an expansion has never been observed in heterometal polyoxovanadate chemistry. The connection mode between cluster anions and complex cations generates two individual layers stacked onto each other. Between the layers weak Sb···O contacts are observed. The crystal water molecules are mainly located in the empty space between the layers. Upon heating H2O molecules are removed, while the crystal structure remains intact. The magnetic behavior is dominated by strong antiferromagnetic exchange interactions between the central V4+ ions, while the interaction between the cluster anion and central Mn2+ ions is significantly less pronounced.

Two germanato-polyoxovanadates with the {V15Ge6O48} cluster core are extended by covalent bonds to four transition metal amine complexes [M(tren)]2+ (M = Co and Zn, tren = tris(2-aminoethyl)amine). The complexes have bonds to terminal atoms of the Ge2O7 units and such expansion of a germanato-polyxovanadate was never observed before. The characterization of these compounds revealed the presence of two protonated tren molecules charge balancing the negative charges of the [{M(tren)}4V15Ge6O48(H2O)]4– anion.

Minimal-nuclearity vanadato-tungstate clusters in [{VIV(dien)}4WVI2O14]·4H2O (1) and [{VIV(dien)}4WVI4O20]·6H2O (2) feature cores of edge-sharing WO6 octahedra, surrounded by a ring of four vanadyl groups. Surprisingly, the V(IV) centers in both 1 and 2 are ferromagnetically coupled, in contrast to all other known vanadato-polyoxotungstates featuring the ubiquituos V–O–W–O–V exchange pathways.

The new tungstovanadate (trenH)2(trenH2)2[W4V13O44]·ca.11H2O was prepared under solvothermal conditions in a basic solution at pH ≈ 12. The cluster core contains VIV/VV centers with delocalized spins exhibiting strong antiferromagnetic exchange interactions as evidenced by temperature-dependent magnetic susceptibility measurements pointing to an S = 1/2 magnetic ground state. The structure features an eight-membered ring composed of four alternating edge-sharing VO5 pyramids and VO6 octahedra encapsulating a central Keggin fragment.

The formation of [{CoII(teta)2}{CoII2(tren)(teta)2}VIV15SbIII6O42(H2O)]·ca.9H2O [teta = triethylenetetraamine; tren = tris(2-aminoethyl)amine] illustrates a strategy toward reducing the molecular charge of polyoxovanadates, a key challenge in their use as components in single-molecule electronics. Here, a V–O–Co bond to a binuclear Co2+-centered complex and a Sb–N bond to the terminal N atom of a teta ligand of a mononuclear Co2+ complex allow for full charge compensation of the archetypal molecular magnet [V15Sb6O42(H2O)]6–. Density functional theory based electron localization function analysis demonstrates that the Sb–N bond has an electron density similar to that of a Sb–O bond. Magnetic exchange coupling between the VIV and CoII spin centers mediated via the Sb–N bridge is comparably weakly antiferromagnetic., Charge neutrality of the [V15Sb6O42(H2O)]6− cluster anion is achieved by simultaneous Sb−N and V−O−Co bond formation. The Sb−N bond has an electron density similar to that of a Sb−O bond. Weak antiferromagnetic exchange interactions are observed between the VIV and CoII spin centers.

The two isostructural complexes MO5V(tren)·H2O (M=Mo (1) and W (2)) were synthesized under solvothermal conditions at pH≈12 crystallizing in the non-centrosymmetric space group P212121. The structures are constructed by a distorted tetrahedral [MO4]2− anion bound via one shared oxygen atom to a severely distorted [VIVN4O]2+ complex completing the octahedral coordination around the V centre. The two O atoms in the VN4O2 octahedron are in cis position. The two compounds represent rare examples where the [MO4]2− anion is acting as a ligand. Both compounds exhibit a piezoelectric effect which is more pronounced for M=Mo. The samples are further characterized with IR and UV/Vis spectroscopy and thermal analysis.

(trenH)2(trenH2)2 [W4V13O44]·≈11H2O (tren: tris(2-aminoethyl)-amine) is prepared under solvothermal conditions by reacting NH4VO3 and WO3 (molar ratio of 1:1.6) in a solution of tren in H2O at pH ≈12 (sealed glass tubes, 130 °C, 3 d, 65% yield based on WO3).

The formation of [{Co

The isostructural compounds (III) and (V) crystallize in the orthorhombic space group P212121 with Z = 4 (single crystal XRD).