arXiv subjects

Changbom Park

Publications and source records attributed to Changbom Park.

At least 73 records · Page 4Linked to original sources

arXiv2023

Low-Surface-Brightness Galaxies are missing in the observed Stellar Mass Function

We investigate the impact of the surface brightness (SB) limit on the galaxy stellar mass functions (GSMFs) using mock surveys generated from the Horizon Run 5 (HR5) simulation. We compare the stellar-to-halo-mass relation, GSMF, and size-stellar mass relation of the HR5 galaxies with empirical data and other cosmological simulations. The mean SB of simulated galaxies are computed using their effective radii, luminosities, and colors. To examine the cosmic SB dimming effect, we compute $k$-corrections from the spectral energy distributions of individual simulated galaxy at each redshift, apply the $k$-corrections to the galaxies, and conduct mock surveys based on the various SB limits. We find that the GSMFs are significantly affected by the SB limits at a low-mass end. This approach can ease the discrepancy between the GSMFs obtained from simulations and observations at $0.625\le z\le 2$. We also find that a redshift survey with a SB selection limit of $\left<μ_r\right>^e =$ 28 mag arcsec${}^{-2}$ will miss 20% of galaxies with $M_\star^g=10^{9}~{\rm M_\odot}$ at $z=0.625$. The missing fraction of low-surface-brightness galaxies increases to 50%, 70%, and 98% at $z=0.9$, 1.1, and 1.9, respectively, at the SB limit.

astro-ph.GA↗

arXiv2023

Tomographic Alcock-Paczynski Test with Redshift-Space Correlation Function: Evidence for the Dark Energy Equation of State Parameter w>-1

The apparent shape of galaxy clustering depends on the adopted cosmology used to convert observed redshift to comoving distance, the $r(z)$ relation, as it changes the line elements along and across the line of sight differently. The Alcock-Paczyński (AP) test exploits this property to constrain the expansion history of the universe. We present an extensive review of past studies on the AP test. We adopt an extended AP test method introduced by Park et al. (2019), which uses the full shape of redshift-space two-point correlation function (CF) as the standard shape, and apply it to the SDSS DR7, BOSS, and eBOSS LRG samples covering the redshift range up to $z=0.8$.We calibrate the test against the nonlinear cosmology-dependent systematic evolution of the CF shape using the Multiverse simulations. We focus on examining whether or not the flat $Λ$CDM `concordance' model is consistent with observation. We constrain the flat $w$CDM model to have $w=-0.892_{-0.050}^{+0.045}$ and $Ω_m=0.282_{-0.023}^{+0.024}$ from our AP test alone, which is significantly tighter than the constraints from the BAO or SNe I$a$ methods by a factor of 3 - 6. When the AP test result is combined with the recent BAO and SNe I$a$ results, we obtain $w=-0.903_{-0.023}^{+0.023}$ and $Ω_m=0.285_{-0.009}^{+0.014}$. This puts a strong tension with the flat $Λ$CDM model with $w=-1$ at $4.2σ$ level. Consistency with $w=-1$ is obtained only when the Planck CMB observation is combined. It remains to see if this tension between observations of galaxy distribution at low redshifts and CMB anisotropy at the decoupling epoch becomes greater in the future studies and leads us to a new paradigm of cosmology.

astro-ph.CO↗

arXiv2022

The first direct measurement of gravitational potential decay rate at cosmological scales and improved dark energy constraint

The integrated Sachs-Wolfe (ISW) effect probes the decay rate ($DR$) of large scale gravitational potential and therefore provides unique constraint on dark energy (DE). However its constraining power is degraded by the ISW measurement, which relies on cross-correlating with the large scale structure (LSS) and suffers from uncertainties in galaxy bias and matter clustering. In combination with lensing-LSS cross-correlation, $DR$ can be isolated in a way free of uncertainties in galaxy bias and matter clustering. We applied this proposal to the combination of the DR8 galaxy catalogue of DESI imaging surveys and Planck cosmic microwave background (CMB) maps. We achieved the first $DR$ measurement, with a total significance of $3.2σ$. We verified the measurements at three redshift bins ($[0.2,0.4)$, $[0.4, 0.6)$, $[0.6,0.8]$), with two LSS tracers (the "low-density points" and the conventional galaxy positions). Despite its relatively low S/N, the addition of $DR$ significantly improves dark energy constraints, over SDSS baryon acoustic oscillation (BAO) data alone or Pantheon supernovae (SN) compilation alone. For flat $w$CDM cosmology, the improvement in the precision of $Ω_m$ is a factor of 1.8 over BAO and 1.5 over SN. For the DE equation of state $w$, the improvement factor is 1.3 over BAO and 1.4 over SN. These improvements demonstrate $DR$ as a useful cosmological probe, and therefore we advocate its usage in future cosmological analysis.

astro-ph.CO↗

arXiv2022

Minkowski Tensors in Redshift Space -- Beyond the Plane Parallel Approximation

The Minkowski tensors (MTs) can be used to probe anisotropic signals in a field, and are well suited for measuring the redshift space distortion (RSD) signal in large scale structure catalogs. We consider how the linear RSD signal can be extracted from a field without resorting to the plane parallel approximation. A spherically redshift space distorted field is both anisotropic and inhomogeneous. We derive expressions for the two point correlation functions that elucidate the inhomogeneity, and then explain how the breakdown of homogeneity impacts the volume and ensemble averages of the tensor Minkowski functionals. We construct the ensemble average of these quantities in curvilinear coordinates and show that the ensemble and volume averages can be approximately equated, but this depends on our choice of definition of the volume average of a tensor and the radial distance between the observer and field. We then extract the tensor Minkowski functionals from spherically redshift space distorted, Gaussian random fields and gravitationally evolved dark matter density fields at $z=0$ to test if we can successfully measure the Kaiser RSD signal. For the dark matter field we find a significant, $\sim 10\%$ anomalous signal in the MT component parallel to the line of sight that is present even on large scales $R_{\rm G} \gtrsim 15 \, {\rm Mpc}$, in addition to the Kaiser effect. This is due to the line of sight component of the MT being significantly contaminated by the Finger of God effect, which can be approximately modelled by an additional damping term in the cumulants.

astro-ph.CO↗

arXiv2022

The Fundamental Plane Is Not a Plane: Warped Nature of the Fundamental Plane of Early-type Galaxies and Its Implication for Galaxy Formation

Based on $16,283$ early-type galaxies (ETGs) in $0.025\le z_\mathrm{spec}<0.055$ from Sloan Digital Sky Survey data, we show that the fundamental plane (FP) of ETGs is not a plane in the strict sense but is a curved surface with a twisted shape whose orthogonal direction to the surface is shifted as the central velocity dispersion ($σ_0$) or mean surface brightness within the half-light radius ($μ_e$) changes. When ETGs are divided into subsamples according to $σ_0$, the coefficient of $μ_e$ of the FP increases, whereas the zero-point of the FP decreases at higher $σ_0$. Taking the $z$ band as an example, the coefficient of $μ_e$ rises from $0.28$ to $0.36$ as $σ_0$ increases from $\sim100$ to $\sim300$ km s$^{-1}$. At the same time, the zero-point of the FP falls from $-7.5$ to $-9.0$ in the same $σ_0$ range. The consistent picture on the curved nature of the FP is also reached by inspecting changes in the FP coefficients for ETG subsamples with different $μ_e$. By examining scaling relations that are projections of the FP, we suggest that the warped nature of the FP may originate from dry merger effects that are imprinted more prominently in ETGs with higher masses.

astro-ph.GA↗

arXiv2022

Formation and Morphology of the First Galaxies in the Cosmic Morning

We investigate the formation and morphological evolution of the first galaxies in the cosmic morning ($10 \gtrsim z \gtrsim 4$) using the Horizon Run 5 (HR5) simulation. For galaxies above the stellar mass $M_{\star, {\rm min}} = 2\times 10^9\,M_{\odot}$, we classify them into disk, spheroid, and irregular types according to their asymmetry and stellar mass morphology. We find that about 2/3 of the galaxies have a Sérsic index $< 1.5$, reflecting the dominance of disk-type morphology in the cosmic morning. The rest are evenly distributed as incidental and transient irregulars or spheroids. These fractions are roughly independent of redshift and stellar mass up to $\sim10^{10}\,M_{\odot}$. Almost all the first galaxies with $M_{\star}> M_{\star, {\rm min}}$ at $z>4$ form at initial peaks of the matter density field. Large-scale structures in the universe emerge and grow like cosmic rhizomes as the underlying matter density fluctuations grow and form associations of galaxies in rare overdense regions and the realm of the galactic world is stretched into relatively lower-density regions along evolving filaments. The cosmic web of galaxies forms at lower redshifts when most rhizomes globally percolate. The primordial angular momentum produced by the induced tidal torques on protogalactic regions is correlated with the internal kinematics of galaxies and tightly aligned with the angular momentum of the total galaxy mass. The large-scale tidal field imprinted in the initial conditions seems responsible for the dominance of disk morphology, and for the tendency of galaxies to re-acquire a disk post-distortion.

astro-ph.GA↗

arXiv2022

A novel approach for calculating galaxy rotation curves using spaxel cross-correlation and iterative smoothing

Precise measurements of the internal dynamics of galaxies have proven of great importance for understanding the internal dark matter distribution of galaxies. We present a novel method for measuring the line-of-sight (LOS) velocities across the face of galaxies by cross-correlation of spectral pixels (spaxels) and an iterative method of smoothing. On simulated data the method can accurately recover the input LOS velocities for different types of spectra (absorption line dominated, emission line dominated, and differing shapes of the continuum), and can handle stellar population radial gradients. Most important of all, it continues to provide reliable measurements of LOS velocities with reasonable uncertainties even when the spectra are very low signal-to-noise (approaching $\sim 1$), which is a challenge for traditional template-fitting approaches. We apply our method to data from a real MaNGA galaxy as a demonstration and find promising results with good precision. This novel approach can be complementary to existing methods primarily based on template fitting.

astro-ph.CO↗

arXiv2021

Evidence for Impact of Galaxy Mergers on Stellar Kinematics of Early-type Galaxies

We provide observational evidence that galaxy mergers significantly affect stellar kinematics of early-type galaxies (ETGs) such as specific stellar angular momentum within the half-light radius ($λ_{R_e}$) and kinematic misalignment ($ψ_\mathrm{mis}$), using MaNGA integral field unit spectroscopic data that are in the Stripe 82 region of the Sloan Digital Sky Survey. In this study, tidal features around ETGs, which are detected in deep coadded images, are used as direct evidence for mergers that occurred recently. In the case of ETGs that do not have dust lanes, $λ_{R_e}$ is lower in ETGs with tidal features than in those without tidal features (median $λ_{R_e}$: $0.21$ versus $0.39$) in all stellar mass and Sérsic index ranges except the most massive bin, so that the fraction of ETGs with tidal features in slow rotators is more than twice as large as that in fast rotators ($42\%$ versus $18\%$). Moreover, ETGs with tidal features have larger $ψ_\mathrm{mis}$ than those without tidal features (mean $ψ_\mathrm{mis}$: $28^\circ$ versus $15^\circ$). By contrast, ETGs with dust lanes are fast rotators, and ETGs with both dust lanes and tidal features have the highest $λ_{R_e}$ (median $λ_{R_e}$: $0.59$) among all ETG categories. In addition, ETGs with dust lanes have small $ψ_\mathrm{mis}$ regardless of the existence of tidal features ($ψ_\mathrm{mis}<7.5^\circ$). Our results can be explained if mergers with different gas fractions generate merger remnants that have different kinematic properties.

astro-ph.GA↗

arXiv2021

Detection of cross-correlation between CMB Lensing and low-density points

Low Density Points (LDPs, \citet{2019ApJ...874....7D}), obtained by removing high-density regions of observed galaxies, can trace the Large-Scale Structures (LSSs) of the universe. In particular, it offers an intriguing opportunity to detect weak gravitational lensing from low-density regions. In this work, we investigate tomographic cross-correlation between Planck CMB lensing maps and LDP-traced LSSs, where LDPs are constructed from the DR8 data release of the DESI legacy imaging survey, with about $10^6$-$10^7$ galaxies. We find that, due to the large sky coverage (20,000 deg$^2$) and large redshift depth ($z\leq 1.2$), a significant detection ($10σ$--$30σ$) of the CMB lensing-LDP cross-correlation in all six redshift bins can be achieved, with a total significance of $\sim 53σ$ over $ \ell\le1024$. Moreover, the measurements are in good agreement with a theoretical template constructed from our numerical simulation in the WMAP 9-year $Λ$CDM cosmology. A scaling factor for the lensing amplitude $A_{\rm lens}$ is constrained to $A_{\rm lens}=1\pm0.12$ for $z<0.2$, $A_{\rm lens}=1.07\pm0.07$ for $0.2<z<0.4$ and $A_{\rm lens}=1.07\pm0.05$ for $0.4<z<0.6$, with the r-band absolute magnitude cut of $-21.5$ for LDP selection. A variety of tests have been performed to check the detection reliability, against variations in LDP samples and galaxy magnitude cuts, masks, CMB lensing maps, multipole $\ell$ cuts, sky regions, and photo-z bias. We also perform a cross-correlation measurement between CMB lensing and galaxy number density, which is consistent with the CMB lensing-LDP cross-correlation. This work therefore further convincingly demonstrates that LDP is a competitive tracer of LSS.

astro-ph.CO↗

arXiv2021

Distance measurements to early-type galaxies by improving the fundamental plane

Using SDSS DR15 to its full extent, we derived fundamental plane distances to over 317 000 early-type galaxies up to a redshift of 0.4. In addition to providing the largest sample of fundamental plane distances ever calculated, as well as a well calibrated group catalogue covering the entire SDSS spectroscopic footprint as far a redshift of 0.5, we present several improvements reaching beyond the traditional definition of the fundamental plane. In one approach, we adjusted the distances by removing systematic biases and selection effects in redshift-magnitude space, thereby greatly improving the quality of measurements. Alternatively, by expanding the traditional fundamental plane by additional terms, we managed to remove systematic biases caused by the selection of our SDSS spectroscopic galaxy sample as well as notably reducing its scatter. We discuss the advantages and caveats of these various methods and calibrations in detail. We found that improving the fundamental plane distance estimates beyond the established methods requires a delicate balancing act between various systematic biases and gains, but managed to reduce the uncertainty of our distance measurements by about a factor of two compared to the traditional fundamental plane.

astro-ph.CO↗

arXiv2021

Rotation Curves of Galaxies and Their Dependence on Morphology and Stellar Mass

We study how stellar rotation curves (RCs) of galaxies are correlated on average with morphology and stellar mass ($M_\mathrm{star}$) using the final release of Sloan Digital Sky Survey IV MaNGA data. We use the visually assigned $T$-types for the morphology indicator, and adopt a functional form for the RC that can model non-flat RCs at large radii. We discover that within the radial coverage of the MaNGA data, the popularly known flat rotation curve at large radii applies only to the particular classes of galaxies, i.e., massive late types ($T$-type $\geq1$, $M_\mathrm{star}\gtrsim10^{10.8}M_\odot$) and S0 types ($T$-type$=-1$ or $0$, $M_\mathrm{star}\gtrsim10^{10.0}M_\odot$). The RC of late-type galaxies at large radii rises more steeply as $M_\mathrm{star}$ decreases, and its slope increases to about $+9$ km s$^{-1}$kpc$^{-1}$ at $M_\mathrm{star}\approx10^{9.7}M_\odot$. By contrast, elliptical galaxies ($T$-type $\le-2$) have descending RCs at large radii. Their slope becomes more negative as $M_\mathrm{star}$ decreases, and reaches as negative as $-15$ km s$^{-1}$kpc$^{-1}$ at $M_\mathrm{star}\approx10^{10.2}M_\odot$. We also find that the inner slope of the RC is highest for elliptical galaxies with $M_\mathrm{star}\approx10^{10.5}M_\odot$, and decreases as $T$-type increases or $M_\mathrm{star}$ changes away from $10^{10.5}M_\odot$. The velocity at the turnover radius $R_t$ is higher for higher $M_\mathrm{star}$, and $R_t$ is larger for higher $M_\mathrm{star}$ and later $T$-types. We show that the inner slope of the RC is coupled with the central surface stellar mass density, which implies that the gravitational potential of central regions of galaxies is dominated by baryonic matter. With the aid of simple models for matter distribution, we discuss what determines the shapes of RCs.

astro-ph.GA↗

arXiv2021

Minkowski Functionals of SDSS-III BOSS : Hints of Possible Anisotropy in the Density Field?

We present measurements of the Minkowski functionals extracted from the SDSS-III BOSS catalogs. After defining the Minkowski functionals, we describe how an unbiased reconstruction of these statistics can be obtained from a field with masked regions and survey boundaries, validating our methodology with Gaussian random fields and mock galaxy snapshot data. From the BOSS galaxy data we generate a set of four density fields in three dimensions corresponding to the northern and southern skies of LOWZ and CMASS catalogs, smoothing over large scales such that the field is perturbatively non-Gaussian. We extract the Minkowski functionals from each data set separately, and measure their shapes and amplitudes by fitting a Hermite polynomial expansion. For the shape parameter of the Minkowski functional curves $a_0$, that is related to the bispectrum of the field, we find that the LOWZ-South data presents a systematically lower value of $a_0 = -0.080 \pm 0.040$ than its northern sky counterpart $a_0 = 0.032 \pm 0.024$. Although the significance of this discrepancy is low, it potentially indicates some systematics in the data or that the matter density field exhibits anisotropy at low redshift. By assuming a standard isotropic flat $Λ$CDM cosmology, the amplitudes of Minkowski functionals from the combination of northern and southern sky data give the constraints $Ω_{\rm c} h^2 n_{\rm s} = 0.110 \pm 0.006$ and $0.111 \pm 0.008$ for CMASS and LOWZ, respectively, which is in agreement with the Planck $Λ$CDM best-fit $Ω_{\rm c}h^{2} n_{\rm s} = 0.116 \pm 0.001$.

astro-ph.CO↗

arXiv2021

Topological Data Analysis of Korean Music in Jeongganbo: A Cycle Structure

Jeongganbo is a unique music representation invented by Sejong the Great. Contrary to the western music notation, the pitch of each note is encrypted and the length is visualized directly in a matrix form in Jeongganbo. We use topological data analysis (TDA) to analyze the Korean music written in Jeongganbo for Suyeonjang, Songuyeo, and Taryong, those well-known pieces played at the palace and among noble community. We are particularly interested in the cycle structure. We first define and determine the node elements of each music, characterized uniquely with its pitch and length. Then we transform the music into a graph and define the distance between the nodes as their adjacent occurrence rate. The graph is used as a point cloud whose homological structure is investigated by measuring the hole structure in each dimension. We identify cycles of each music, match those in Jeongganbo, and show how those cycles are interconnected. The main discovery of this work is that the cycles of Suyeonjang and Songuyeo, categorized as a special type of cyclic music known as Dodeuri, frequently overlap each other when appearing in the music while the cycles found in Taryong, which does not belong to Dodeuri class, appear individually.

cs.SD↗

arXiv2021

PSF Deconvolution of the IFU Data and Restoration of Galaxy Stellar Kinematics

We present a performance test of the Point Spread Function deconvolution algorithm applied to astronomical Integral Field Unit (IFU) Spectroscopy data for restoration of galaxy kinematics. We deconvolve the IFU data by applying the Lucy-Richardson algorithm to the 2D image slice at each wavelength. We demonstrate that the algorithm can effectively recover the true stellar kinematics of the galaxy, by using mock IFU data with diverse combination of surface brightness profile, S/N, line-of-sight geometry and Line-Of-Sight Velocity Distribution (LOSVD). In addition, we show that the proxy of the spin parameter $λ_{R_{e}}$ can be accurately measured from the deconvolved IFU data. We apply the deconvolution algorithm to the actual SDSS-IV MaNGA IFU survey data. The 2D LOSVD, geometry and $λ_{R_{e}}$ measured from the deconvolved MaNGA IFU data exhibit noticeable difference compared to the ones measured from the original IFU data. The method can be applied to any other regular-grid IFU data to extract the PSF-deconvolved spatial information.

astro-ph.GA↗

arXiv2021

Evolution of the spin of late-type galaxies caused by galaxy-galaxy interactions

We use N-body/hydrodynamic simulations to study the evolution of the spin of a Milky Way-like galaxy through interactions. We perform a controlled experiment of co-planner galaxy-galaxy encounters and study the evolution of disk spins of interacting galaxies. Specifically, we consider the cases where the late-type target galaxy encounters an equally massive companion galaxy, which has either a late or an early-type morphology, with the closest approach distance of about 50 kpc, in prograde or retrograde sense. By examining the time change of the circular velocity of the disk material of the target galaxy from each case, we find that the target galaxy tends to lose the spin through prograde collisions but hardly through retrograde collisions, regardless of the companion galaxy type. The decrease of the spin results mainly from the deflection of the orbit of the disk material by tidal disruption. Although there is some disk material which gains the circular velocity through hydrodynamic as well as gravitational interactions or by transferring material from the companion galaxy, it turns out that the amount of the material is generally insufficient to increase the overall galactic spin under the conditions we set. It is found that the spin angular momentum of the target galaxy disk decreases by 15 - 20% after a prograde collision. We conclude that the accumulated effects of galaxy-galaxy interactions will play an important role in determining the total angular momentum of late-type galaxies at current stage.

astro-ph.GA↗

arXiv2021

Identification of Cosmic Voids as Massive Cluster Counterparts

We develop a method to identify cosmic voids from the matter density field by adopting a physically-motivated concept that voids are the counterpart of massive clusters. To prove the concept we use a pair of $Λ$CDM simulations, a reference and its initial density-inverted mirror simulation, and study the relation between the effective size of voids and the mass of corresponding clusters. Galaxy cluster-scale dark matter halos are identified in the Mirror simulation at $z=0$ by linking dark matter particles. The void corresponding to each cluster is defined in the Reference simulation as the region occupied by the member particles of the cluster. We study the voids corresponding to the halos more massive than $10^{13}h^{-1}M_{\odot}$. We find a power-law scaling relation between the void size and the corresponding cluster mass. Voids with corresponding cluster mass above $10^{15}h^{-1}M_{\odot}$ occupy $\sim1\%$ of the total simulated volume, whereas this fraction increases to $\sim54\%$ for voids with corresponding cluster mass above $10^{13}h^{-1}M_{\odot}$. It is also found that the density profile of the identified voids follows a universal functional form. Based on these findings, we propose a method to identify cluster-counterpart voids directly from the matter density field without their mirror information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We recover voids corresponding to clusters more massive than $3\times10^{14}h^{-1}M_{\odot}$ at 70--74 \% level of completeness and reliability. Our results suggest that we are able to identify voids in a way to associate them with clusters of a particular mass-scale.

astro-ph.CO↗

arXiv2021

Cosmological Parameter Estimation from the Two-Dimensional Genus Topology -- Measuring the Expansion History using the Genus Amplitude as a Standard Ruler

We measure the genus of the galaxy distribution in two-dimensional slices of the SDSS-III BOSS catalog to constrain the cosmological parameters governing the expansion history of the Universe. The BOSS catalogs are divided into twelve concentric shells over the redshift range $0.25 < z < 0.6$ and we repeatedly measure the genus from the two-dimensional galaxy density fields, each time varying the cosmological parameters used to infer the distance-redshift relation to the shells. We also indirectly reconstruct the two-dimensional genus amplitude using the three-dimensional genus measured from SDSS Main Galaxy Sample with galaxies at low redshift $z < 0.12$. We combine the low- and high-redshift measurements, finding the cosmological model which minimizes the redshift evolution of the genus amplitude, using the fact that this quantity should be conserved. Being a distance measure, the test is sensitive to the matter density parameter ($Ω_{\rm m}$) and equation of state of dark energy ($w_{\rm de}$). We find a constraint of $w_{\rm de} = -1.05^{+0.13}_{-0.12}$, $Ω_{\rm m} = 0.303 \pm 0.036$ after combining the high- and low-redshift measurements and combining with Planck CMB data. Higher redshift data and combining data sets at low redshift will allow for stronger constraints.

astro-ph.CO↗

arXiv2020

A novel probe of bubble size statistics and time scales of the epoch of reionization using the contour Minkowski Tensor

We employ the rank-2 {\em contour} Minkowski Tensor in two dimensions to probe length and time scales of ionized bubbles during the epoch of reionization. We demonstrate that the eigenvalues of this tensor provide excellent probes of the distribution of the sizes of ionized bubbles, and from it the characteristic bubble sizes, at different redshifts. We show that ionized bubbles are not circular, and hence not spherical in three dimensions, as is often assumed for simplified analytic arguments. We quantify their shape anisotropy by using the ratio of the two eigenvalues. The shape parameter provides the characteristic time epochs when bubble mergers begin and end. Our method will be very useful to reconstruct the reionization history using data of the brightness temperature field.

astro-ph.CO↗