Number Density Maps Research Articles

A trail of the invisible: blue globular clusters trace the radial density distribution of the dark matter – case study of NGC 4278

ABSTRACTWe present new, deep optical observations of the early-type galaxy NGC 4278, which is located in a small loose group. We find that the galaxy lacks fine substructure, that is, it appears relaxed, out to a radius of ∼70 kpc. Our g- and i-band surface brightness profiles are uniform down to our deepest levels of ∼28 mag arcsec−2. This spans an extremely large radial range of more than 14 half-mass radii. Combined with archival globular cluster (GC) number density maps and a new analysis of the total mass distribution obtained from archival Chandra X-ray data, we find that the red GC subpopulation traces well the stellar mass density profile from 2.4 out to even 14 half-mass radii, while the blue GC subpopulation traces the total mass density profile of the galaxy over a large radial range. Our results reinforce the scenario that red GCs form mostly in situ along with the stellar component of the galaxy, while the blue GCs are more closely aligned with the total mass distribution in the halo and were accreted along with halo matter. We conclude that for galaxies where the X-ray emission from the hot halo is too faint to be properly observable and as such is not available to measure the dark matter profile, the blue GC population can be used to trace this dark matter component out to large radii.

Detection of Intracluster Globular Clusters in the First JWST Images of the Gravitational Lens Cluster SMACS J0723.3–7327 at z = 0.39

We present a survey of globular clusters (GCs) in the massive gravitational lens cluster SMACS J0723.3–7327 at z = 0.39 based on the early released JWST/NIRCam images. In the color–magnitude diagrams of the point sources, we clearly find a rich population of intracluster GCs that are spread over a wide area of the cluster. Their ages, considering the cluster redshift, are younger than 9.5 Gyr. The F200W (AB) magnitudes of these GCs, 26.5 mag < F200W0 < 29.5 mag, correspond to −15.2 mag < M F200W < −12.2 mag, showing that they belong to the brightest GCs (including ultracompact dwarfs). The spatial distributions of these GCs show a megaparsec-scale structure elongated along the major axis of the brightest cluster galaxy. In addition, they show a large number of substructures, some of which are consistent with the substructures seen in the map of diffuse intracluster light. The GC number density map is, in general, consistent with the dark matter mass density map based on the strong lensing analysis in the literature. The radial number density profile of the GCs in the outer region is steeper than the dark matter mass profile obtained from lensing models. These results are consistent with those for the GCs found in the deep HST images of A2744, another massive cluster at z = 0.308, and in simulated galaxy clusters. This shows that the intracluster GCs are an excellent independent tool to probe the dark matter distribution in galaxy clusters, as well as reveal the cluster assembly history in the JWST era.

Spatial Distribution of Dark Matter in and Around Galaxy Clusters Traced by Galaxies, Gas, and Intracluster Stars in a Simulated Universe

To understand how well galaxies, gas, and intracluster stars trace dark matter in and around galaxy clusters, we use the IllustrisTNG cosmological hydrodynamical simulation and compare the spatial distribution of dark matter with that of baryonic components in clusters. To quantify the global morphology of the density distribution of each component in clusters, we fit an ellipse to the density contour of each component and derive shape parameters at different radii. We find that the ellipticity of dark matter is better correlated with that of galaxy mass-weighted number density, rather than with that of galaxy number density or galaxy velocity dispersion. We thus use the galaxy mass-weighted number density map as representative of the galaxy maps. Among three different density maps from galaxies, gas, and intracluster stars, the ellipticity of dark matter is best reproduced by that of the galaxy map over the entire radii. The virialized galaxy clusters show a better correlation of spatial distribution between dark matter and other components than the unvirialized clusters, suggesting that it requires some time for each component to follow the spatial distribution of dark matter after merging events. Our results demonstrate that galaxies are still good tracers of dark matter distribution even in the nonlinear regime corresponding to the scales in and around galaxy clusters, being consistent with the case where galaxies trace well the matter distribution on cosmologically large scales.

Research on the phase structure of Styrene-Butadiene-Styrene modified asphalt based on molecular dynamics

To study the phase structure of the SBS modified asphalt by considering the polymer characteristic of liner SBS molecular with different block ratios and concentrations on the molecular scale. A total of 18 molecular dynamics(MD) models were constructed by Gromacs. The phase phenomenon was analyzed by number density and density distribution map. The adsorption behavior of SARA components and SBS were analyzed by considering the SARA molecules' contact characteristics and the adsorption number of SARA molecules on the SBS surface. The result shows that SBS molecular will form the dispersed phase in low concentration (0–4%). With the concentration increasing, the phase will transfer from the dispersed phase to the continuous phase. After the critical concentration, the state of SBS molecule changes from the stable state to the dispersed phase. the SBS with S: B block ratio closer to the middle point is easier to form a continuous phase in different concentrations. The asphaltenes aggregation would also be attracted by SBS, and interact with SBS by branch chains. The saturates molecular is wrapped around the SBS molecules. Resins and aromatics molecules with higher degrees of freedom in space and easy to adjust their spatial structure are also more likely to adsorb around SBS molecules. The highest adsorbed molecules number and molecular weight of different SBS molecules are the Resins, followed by the aromatics. The amount of the adsorbed asphaltenes is nearly the same as that of the saturates. Due to the highest weight of asphaltene molecules in the SARA component, the asphaltene molecular weight absorbed by SBS is close to that of aromatics. The phase structure change may cause a dramatic change in the number of adsorbed molecules.

Spatial Orientations of Angular Momentum Vectors of Galaxies in Supercluster S [195+027+0022] and Substructure

This paper presents an analysis of the spin vector orientations of SDSS (Sloan Digital Sky Survey) galaxies in the Supercluster S [195+027+0022] using the seventh data release (2008 October). By using the spectroscopic database of galaxies, identified number density map in the region of Superclusters. Several density enhancements are observed, suggesting the possibility of substructure in the Supercluster. Two-dimensional observed parameters that we received from the database are used to compute three-dimensional galaxy rotation axes by applying `position angle-inclination' method. Apply the selection effects by performing the random simulation method. The expected distribution curves are obtained from the simulation. Chi-square, auto-correlation, and Fourier tests are used to examine non-random effects in the polar and azimuthal angle distributions of the galaxy rotation axes. To check these results with the different galaxy evolution models namely Hierarchy, Primordial, and Pancake model. The result supports the Hierarchy model.

Layered graphene oxide membranes functioned by amino acids for efficient separation of metal ions

As a kind of heavy metal, lead ions (Pb2+) are a great threat to human health and the ecological environment. Due to their excellent properties, graphene and its derivatives are expected to be used for water purification. Amino acid functional groups were designed for graphene oxide membranes via dehydration condensation. The effects of the amino acid groups on the membrane performance for separating metal ions were investigated by the molecular dynamics. Under the premise that the water permeability is basically the same, the retention rate for Pb2+ by alanine groups with negatively charged terminals is 1.6 times of that by the carboxyl groups. The number-density map and the radial distribution function indicate that a large area of local high-density regions of Pb2+ will be formed around the negatively charged alanine groups. At the same time, the diffusion coefficient for Pb2+ and Na+ can be effectively reduced by the electrostatic attraction of the negative groups. It is concluded that functioned by the negatively charged alanine, the retention rate for metal ions by the layered graphene oxide membranes can be significantly improved at the cost of a little loss in water permeability.

Encapsulation of single-walled carbon nanotubes with asymmetric pyrenyl-gemini surfactants

Whereas the encapsulation technology of surfactants coating on the surface of single-walled carbon nanotubes (SWCNTs) attracts much attention, the mechanisms of asymmetric surfactants interacting with the SWCNTs and their molecular structures are rarely reported. Herein, we report a molecular dynamics (MD) simulation study on the investigation of surfactant adsorption and induced colloidal stability onto different SWCNTs. The surfactant-based encapsulation system, originating from the complementary π-π stacking, is validated through two-dimensional number density maps. We find that the asymmetric pyrenyl-gemini surfactants (APGSs) form double-layer assembled architecture films on nanotube surface. The inner layers of the films are packed with the pyrenyl groups of APGSs, which interact with SWCNTs via π-π stacking, while the outer layers composed of alkyl chains of APGSs coat at the nanotube surface through van der Waals interactions. In addition, we observe a configurational transformation of APGSs on the SWCNT surface from the folding configuration to unfolding patterns, when increasing the nanotube radius or the surface coverage of APGSs. Our study provides helpful insights into the encapsulation mechanism of APGSs on the SWCNT surface and the design of highly selective dispersants for SWCNTs.

Multitracer CMB delensing maps from Planck and WISE data

Delensing, the removal of the limiting lensing $B$-mode background, is crucial for the success of future cosmic microwave background (CMB) surveys in constraining inflationary gravitational waves (IGWs). In recent work, delensing with large-scale structure tracers has emerged as a promising method both for improving constraints on IGWs and for testing delensing methods for future use. However, the delensing fractions (i.e., the fraction of the lensing-$B$ mode power removed) achieved by recent efforts have been only 20%--30%. In this work, we provide a detailed characterization of a full-sky, dust-cleaned cosmic infrared background (CIB) map for delensing and construct a further-improved delensing template by adding additional tracers to increase delensing performance. In particular, we build a multitracer delensing template by combining the dust-cleaned Planck CIB map with a reconstructed CMB lensing map from Planck and a galaxy number density map from the Wide-field Infrared Survey Explorer (WISE) satellite. For this combination, we calculate the relevant weightings by fitting smooth templates to measurements of all the cross-spectra and autospectra of these maps. On a large fraction of the sky (${f}_{\mathrm{sky}}=0.43$), we demonstrate that our maps are capable of providing a delensing factor of $43\ifmmode\pm\else\textpm\fi{}1%$; using a more restrictive mask (${f}_{\mathrm{sky}}=0.11$), the delensing factor reaches $48\ifmmode\pm\else\textpm\fi{}1%$. For low-noise surveys, our delensing maps, which cover much of the sky, can thus improve constraints on the tensor-to-scalar ratio ($r$) by nearly a factor of 2. The delensing tracer maps are made publicly available, and we encourage their use in ongoing and upcoming $B$-mode surveys.

Molecular dynamics study of room temperature ionic liquids with water at mica surface

Water in room temperature ionic liquids (RTILs) could impose significant effects on their interfacial properties at a charged surface. Although the interfaces between RTILs and mica surfaces exhibit rich microstructure, the influence of water content on such interfaces is little understood, in particular, considering the fact that RTILs are always associated with water due to their hygroscopicity. In this work, we studied how different types of RTILs and different amounts of water molecules affect the RTIL-mica interfaces, especially the water distribution at mica surfaces, using molecular dynamics (MD) simulation. MD results showed that (1) there is more water and a thicker water layer adsorbed on the mica surface as the water content increases, and correspondingly the average location of K+ ions is farther from mica surface; (2) more water accumulated at the interface with the hydrophobic [Emim][TFSI] than in case of the hydrophilic [Emim][BF4] due to the respective RTIL hydrophobicity and ion size. A similar trend was also observed in the hydrogen bonds formed between water molecules. Moreover, the 2D number density map of adsorbed water revealed that the high-density areas of water seem to be related to K+ ions and silicon/aluminum atoms on mica surface. These results are of great importance to understand the effects of hydrophobicity/hydrophicility of RTIL and water on the interfacial microstructure at electrified surfaces.

Specific Frequencies and Luminosity Profiles of Cluster Galaxies and Intracluster Light in Abell 1689

Abstract We present magnitudes and profile fits for 180 galaxies in the central field of the massive lensing cluster Abell 1689 using very deep imaging with the Hubble Space Telescope Advanced Camera for Surveys in the F814W bandpass. Previous work revealed an exceptionally large number of globular clusters (GCs) in A1689 and mapped their number density distribution. We decompose this number density map into GCs associated with individual cluster galaxies and ICGCs (intracluster GCs) associated with the intracluster light (ICL). In all, we measure GC specific frequencies S N for 33 cluster members and the ICL. The relation between S N and galaxy magnitude is consistent with the trend observed in Virgo, although some intermediate-luminosity galaxies scatter to S N &gt; 10 . We estimate that the ICL makes up 11% of the starlight in this field, whereas the ICGCs account for ∼35% of the GCs, both consistent with predictions from simulations. Galaxies with higher S N values tend to be rounder, and there is a marginally significant trend of decreasing S N with increasing specific angular momenta λ R . We also reevaluate the GC population in the A2744 Frontier Field, for which fewer than 1/10 as many GCs have been detected because of its larger distance. Finally, our core-Sérsic fit to the light profile of the A1689 brightest cluster galaxy implies a break radius of 3.8 kpc, among the largest known; we discuss implications of the sizable core and extensive GC population for the supermassive black hole in light of scaling relations.

Preferred alignments of angular momentum vectors of galaxies in six dynamically unstable Abell clusters

A spatial orientation of angular momentum vectors of galaxies in six dynamically unstable Abell clusters (S1171, S0001, A1035, A1373, A1474 and A4053) is studied. For this, two-dimensional observed parameters (e.g., positions, diameters and position angles) are converted into three-dimensional (3D) rotation axes of the galaxy using the ‘position angle - inclination’ method. The expected isotropic distribution curves for angular momentum vectors are obtained by performing random simulations. The observed and expected distributions are compared using several statistical tests. No preferred alignments of angular momentum vectors of galaxies are noticed in all six dynamically unstable clusters, supporting the hierarchy model of galaxy formation. These clusters have a larger value of velocity dispersion. However, local effects are noticed in the clusters that have substructures in the 1D-3D number density maps.

Low-frequency radio constraints on the synchrotron cosmic web

We present a search for the synchrotron emission from the synchrotron cosmic web by cross correlating 180MHz radio images from the Murchison Widefield Array with tracers of large scale structure (LSS). We use two versions of the radio image covering $21.76\times 21.76$ degrees with point sources brighter than 0.05 Jy subtracted, with and without filtering of Galactic emission. As tracers of the LSS we use the Two-Micron-All-Sky-Survey (2MASS) and the Widefield InfraRed Explorer (WISE) redshift catalogues to produce galaxy number density maps. The cross correlation functions all show peak amplitudes at zero degrees, decreasing with varying slopes towards zero correlation over a range of one degree. The cross correlation signals include components from point source, Galactic, and extragalactic diffuse emission. We use models of the diffuse emission from smoothing the density maps with Gaussians of sizes 1-4 Mpc to find limits on the cosmic web components. From these models we find surface brightness 99.7 per cent upper limits in the range of 0.09-2.20 mJy beam$^{-1}$ (average beam size of 2.6 arcmin), corresponding to 0.01-0.30 mJy arcmin$^{-2}$. Assuming equipartition between energy densities of cosmic rays and the magnetic field, the flux density limits translate to magnetic field strength limits of 0.03-1.98 $\mu$G, depending heavily on the spectral index. We conclude that for a 3$\sigma$ detection of 0.1 $\mu$G magnetic field strengths via cross correlations, image depths of sub-mJy to sub-$\mu$Jy are necessary. We include discussion on the treatment and effect of extragalactic point sources and Galactic emission, and next steps for building on this work.

Machine learning etudes in astrophysics: selection functions for mock cluster catalogs

Making mock simulated catalogs is an important component of astrophysical data analysis. Selection criteria for observed astronomical objects are often too complicated to be derived from first principles. However the existence of an observed group of objects is a well-suited problem for machine learning classification. In this paper we use one-class classifiers to learn the properties of an observed catalog of clusters of galaxies from ROSAT and to pick clusters from mock simulations that resemble the observed ROSAT catalog. We show how this method can be used to study the cross-correlations of thermal Sunya'ev-Zeldovich signals with number density maps of X-ray selected cluster catalogs. The method reduces the bias due to hand-tuning the selection function and is readily scalable to large catalogs with a high-dimensional space of astrophysical features.

COMPARING DENSE GALAXY CLUSTER REDSHIFT SURVEYS WITH WEAK-LENSING MAPS

We use dense redshift surveys of nine galaxy clusters at $z\sim0.2$ to compare the galaxy distribution in each system with the projected matter distribution from weak lensing. By combining 2087 new MMT/Hectospec redshifts and the data in the literature, we construct spectroscopic samples within the region of weak-lensing maps of high (70--89%) and uniform completeness. With these dense redshift surveys, we construct galaxy number density maps using several galaxy subsamples. The shape of the main cluster concentration in the weak-lensing maps is similar to the global morphology of the number density maps based on cluster members alone, mainly dominated by red members. We cross correlate the galaxy number density maps with the weak-lensing maps. The cross correlation signal when we include foreground and background galaxies at 0.5$z_{\rm cl}<z<2z_{\rm cl}$ is $10-23$% larger than for cluster members alone at the cluster virial radius. The excess can be as high as 30% depending on the cluster. Cross correlating the galaxy number density and weak-lensing maps suggests that superimposed structures close to the cluster in redshift space contribute more significantly to the excess cross correlation signal than unrelated large-scale structure along the line of sight. Interestingly, the weak-lensing mass profiles are not well constrained for the clusters with the largest cross correlation signal excesses ($>$20% for A383, A689 and A750). The fractional excess in the cross correlation signal including foreground and background structures could be a useful proxy for assessing the reliability of weak-lensing cluster mass estimates.

X-RAY SUBSTRUCTURE STUDIES OF FOUR GALAXY CLUSTERS USINGXMM-NEWTONDATA

Mahdavi et al. find that the degree of agreement between weak lensing and X-ray mass measurements is a function of cluster radius. Numerical simulations also point out that X-ray mass proxies do not work equally well at all radii. The origin of the effect is thought to be associated with cluster mergers. Recent work presenting the cluster maps showed an ability of X-ray maps to reveal and study cluster mergers in detail. Here we present a first attempt to use the study of substructure in assessing the systematics of the hydrostatic mass measurements using two-dimensional (2-D) X-ray diagnostics. The temperature map is uniquely able to identify the substructure in an almost relaxed cluster which would be unnoticed in the ICM electron number density and pressure maps. We describe the radial fluctuations in the 2-D maps by a cumulative/differential scatter profile relative to the mean profile within/at a given radius. The amplitude indicates ~10 fluctuations in the temperature, electron number density and entropy maps, and ~15 fluctuations in the pressure map. The amplitude of and the discontinuity in the scatter complement 2-D substructure diagnostics, e.g. indicating the most disturbed radial range. There is a tantalizing link between the substructure identified using the scatter of the entropy and pressure fluctuations and the hydrostatic mass bias relative to the expected mass based on the M-Yx and M-Mgas relations particularly at r500. XMM-Newton observations with ~120,000 source photons from the cluster are sufficient to apply our substructure diagnostics via the spectrally measured 2-D temperature, electron number density, entropy and pressure maps.

Washington CCD Photometry of the Globular Cluster System of the Giant Elliptical Galaxy M60 in Virgo

We present a photometric study of the globular clusters in the giant elliptical galaxy M60 in the Virgo cluster, based on deep, relatively wide field Washington CT_1 CCD images. The color-magnitude diagram reveals a significant population of globular clusters in M60, and a large number of young luminous clusters in NGC 4647, a small companion spiral galaxy north-west of M60. The color distribution of the globular clusters in M60 is clearly bimodal, with a blue peak at (C-T_1)=1.37, and a red peak at (C-T_1)=1.87. We derive two new transformation relations between the (C-T_1)_0 color and [Fe/H] using the data for the globular clusters in our Galaxy and M49. Using these relations we derive the metallicity distribution of the globular clusters in M60, which is also bimodal: a dominant metal-poor component with center at [Fe/H]=-1.2, and a weaker metal-rich component with center at [Fe/H]=-0.2. The radial number density profile of the globular clusters is more extended than that of the stellar halo, and the radial number density profile of the blue globular clusters is more extended than that of the red globular clusters. The number density maps of the globular clusters show that the spatial distribution of the blue globular clusters is roughly circular, while that of the red globular cluster is elongated similarly to that of the stellar halo. We estimate the total number of the globular clusters in M60 to be 3600+/-500$,and the specific frequency to be S_N=3.8+/-0.4. The mean color of the bright blue globular clusters gets redder as they get brighter in both the inner and outer region of M60. This blue tilt is seen also in the outer region of M49, the brightest Virgo galaxy. Implications of these results are discussed.

Witnessing the Formation of a Galaxy Cluster atz= 0.485: Optical and X‐Ray Properties of RX J1117.4+0743 ([VMF 98] 097)

We present a multiwavelength study of the poor cluster RX J1117.4+0743 ([VMF 98] 097) at z = 0.485, based on GMOS/Gemini South g' and r' photometry and spectroscopy, and XMM-Newton observations. We examine its nature and surroundings by analyzing the projected galaxy distribution, the galaxy velocity distribution, the weak-lensing mass reconstruction, and the X-ray spectroscopy and imaging. The cluster is composed by at least two structures along the line of sight, with ?V = 592 ? 82 and 391 ? 85 km s-1, respectively. Other structures are also detected in X-ray, in the galaxy projected number density map, and by weak lensing. The derived temperature and bolometric X-ray luminosity reveal that [VMF 98] 097 behaves like a normal cluster, in agreement with LX-TX correlation found for z = 0 and at z ~ 0.4 clusters. The mass determination inferred from weak lensing is on average 3-4.8 times higher than the X-ray mass. We have two possible explanations for this discrepancy: (1) the cluster is in nonequilibrium, then the deviation of the X-ray estimated mass from the true value can be as high as a factor of 2; (2) the intervening mass along the line of sight of the cluster is producing an overestimation of the weak-lensing mass. Based on the analysis, we conclude that [VMF 98] 097 is a perturbed cluster with at least two substructures in velocity space and with other nearby structures at projected distances of about 1 h Mpc. This is an example of a poor cluster caught in the process of accreting substructures to become a rich cluster.

The impact of spheroid stars for Macho microlensing surveys of the Andromeda galaxy

The Andromeda galaxy (M31) is an important test case for a number of microlensing surveys looking for massive compact halo objects (Machos). A long-standing theoretical prediction is that the high inclination of the M31 disc should induce an asymmetry in the spatial distribution of M31 Macho events, whereas the distribution of variable stars and microlensing events in the M31 disc should be symmetric. We examine the role of stars in the M31 visible spheroid as both lenses and sources to microlensing events. We compute microlensing event number density maps and estimate pixel-lensing rates and event durations for three-component models of M31 which are consistent with the observed rotation curve, surface brightness profile and dynamical mass estimates. Three extreme models are considered: a massive spheroid model; a massive disc model; and a massive Macho halo model. An important consequence of the spheroid is that, even if Machos are absent in M31, an asymmetric spatial signature is still generally expected from stellar lensing alone. The lensing of disc sources by spheroid stars produces an asymmetry of the same sign as that of Machos, whereas lensing by disc stars against spheroid sources produces an asymmetry of the opposite sign. The relative mass-to-light ratio of the spheroid and disc populations controls which of these signatures dominates the overall stellar spatial distribution. We find that the inclusion of the spheroid weakens the M31 Macho spatial asymmetry by about 20–30 per cent over a disc-only asymmetry for the models considered. We also find for our models that Machos dominate over most of the far disc, provided that they contribute at least ∼ 25 per cent of the halo dark matter density. This is a conservative limit because many stellar events are too short to be detected by present surveys. The presence of the spheroid also has beneficial consequences for M31 lensing surveys. The stellar spatial asymmetry is likely to be important in distinguishing a spheroidal Macho halo from a highly flattened halo or from a dark-matter-dominated disc, because spatial asymmetries of opposing signs are expected in these cases.

Wide-Field CCD Photometry of the Globular Cluster M92

We present wide field CCD photometry of a galactic globular cluster M92 obtained in the V and I bands with the CFH12K mosaic CCD at the Canada-France-Hawaii Telescope. A well-defined color-magnitude diagram is derived down to 5 magnitudes fainter than the cluster main sequence turn-off. After removing the background contribution, we obtain luminosity and mass functions, surface density profiles, and the surface number density maps of the stars belonging to the cluster. The surface density profile of all stars shows that the cluster's halo extends at least out to ~30' from the cluster center in agreement with previous study, but the profile of faint stars at the very outer region of the cluster shows a different gradient compared with that of bright stars. For a mass function of the cluster, we find that the inner region of the cluster has x = 1.2+-0.2, whereas the outer region has x = 1.8 +-0.3, clearly indicating a mass segregation of the cluster. An estimate of the photometric mass of the cluster implies that the remnant populations (white dwarfs and neutron stars) contribute at least 25% of the total cluster mass. The surface density map of M92 shows some evidence that the tidal tail of M92 may be oriented perpendicular to the direction toward the Galactic center.

Laser-induced fluorescence probing during pulsed-laser ablation for three-dimensional number density mapping of plasma species

Laser-induced fluorescence spectroscopy was employed to measure ground state number densities of atoms and molecules in plasma plumes generated by pulsed-laser ablation of Al, C and Ti targets in N2 or O2 low-pressure atmospheres. A beam expander was used to transform the dye laser beam in a thin plane section of 0.2×40 mm2 dimension crossing the plasma through its symmetry axis. Using a fast intensified charged coupled device matrix for fluorescence detection, three-dimensional number density mapping of plasma species was acquired. Calibration of the measured ground state densities in an absolute scale was performed by additional absorption measurements. According to the plasma temperature, the density of atoms and molecules and their total number in the plasma plume were estimated. The species densities were compared to those obtained by intensity calibrated emission spectroscopic measurements. The time- and space-evolution of atomic and molecular densities gives information about gas-phase reactions due to the interaction of the ablated material with the surrounding low-pressure gas. The results contribute to a better understanding of thin film synthesis by reactive pulsed-laser deposition.