Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q band
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Matthew A. Petroff↗
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Observations of blazars with ASCA
The Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of 3C 279, Mkn 421, PKS 2155-304, BL Lac 0716+714 and OJ 287 blazars are presented. Blazars are a class of active galactic nuclei characterized by high variability, high polarization, flat radio spectrum and featureless spectrum. The X-ray spectra and flux variations of blazars are discussed. The inverse correlation between X-ray flux and index, soft lag, the convex curvature of the spectrum, flat gamma-ray and/or X-ray spectra, fast variability and featureless spectrum are common characteristics of blazars.
Makino, F.↗
Correlations in the (Sub)Mil1imeter Background from ACT x BLAST
We present measurements of the auto- and cross-frequency correlation power spectra of the cosmic (sub)millimeter background at: 250, 350, and 500 microns (1200, 860, and 600 GHz) from observations made with the Balloon-borne Large Aperture Submillimeter Telescope, BLAST; and at 1380 and 2030 microns (218 and 148 GHz) from observations made with the Atacama Cosmology Telescope, ACT. The overlapping observations cover 8.6 deg(sup 2) in an area relatively free of Galactic dust near the south ecliptic pole (SEP). The ACT bands are sensitive to radiation from the CMB, the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio and dusty star-forming galaxies (DSFGs), while the dominant contribution to the BLAST bands is from DSFGs. We confirm and extend the BLAST analysis of clustering with an independent pipeline, and also detect correlations between the ACT and BLAST maps at over 25(sigma) significance, which we interpret as a detection of the DSFGs in the ACT maps. In addition to a Poisson component in the cross-frequency power spectra, we detect a clustered signal at 4(sigma), and using a model for the DSFG evolution and number counts, we successfully fit all our spectra with a linear clustering model and a bias that depends only on red shift and not on scale. Finally, the data are compared to, and generally agree with, phenomenological models for the DSFG population. This study represents a first of its kind, and demonstrates the constraining power of the cross-frequency correlation technique to constrain models for the DSFGs. Similar analyses with more data will impose tight constraints 011 future models.
Hajian, Amir↗
ASCA Observation of the Quiescent X-ray Counterpart to SGR 1627-41
We present a 2-10 keV ASCA (Advanced Satellite for Cosmology and Astrophysics) observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux equal to approximately 5 x 10(exp -12) ergs cm(exp -2) s(exp -1). We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations.
Hurley, K.↗
A Newly Discovered Supernova Remnant and MSH 11-62 and 3C58
CTA 1 is a center-filled supernova remnant (SNR) whose morphology and spectrum indicate the presence of a central pulsar, a synchrotron nebula, and a thermal component associated with the expansion of the blast wave into the interstellar medium. The centrally bright emission surrounds the position of a faint point source of X-rays observed with the ROSAT Position Sensitive Proportional Counter (PSPC). Here we report on Advanced Spacecraft for Cosmology Astrophysics (ASCA) observations that confirm the nonthermal nature of the diffuse emission from the central regions of the remnant. We also present evidence for weak thermal emission that appears to increase in strength toward the outer boundary of the SNR. Thus, CTA 1 appears to be an X-ray composite remnant. Both the aftermath of the explosive supernova event and the energetic compact core are observable.
Slane, Patrick O.↗
Gravitational radiation, inspiraling binaries, and cosmology
We show how to measure cosmological parameters using observations of inspiraling binary neutron star or black hole systems in one or more gravitational wave detectors. To illustrate, we focus on the case of fixed mass binary systems observed in a single Laser Interferometer Gravitational-wave Observatory (LIGO)-like detector. Using realistic detector noise estimates, we characterize the rate of detections as a function of a threshold SNR Rho(0), H0, and the binary 'chirp' mass. For Rho(0) = 8, H0 = 100 km/s/Mpc, and 1.4 solar mass neutron star binaries, the sample has a median redshift of 0.22. Under the same assumptions but independent of H0, a conservative rate density of coalescing binaries implies LIGO will observe about 50/yr binary inspiral events. The precision with which H0 and the deceleration parameter q0 may be determined depends on the number of observed inspirals. For fixed mass binary systems, about 100 observations with Rho(0) = 10 in the LIGO will give H0 to 10 percent in an Einstein-DeSitter cosmology, and 3000 will give q0 to 20 percent. For the conservative rate density of coalescing binaries, 100 detections with Rho(0) = 10 will require about 4 yrs.
Chernoff, David F.↗
BeppoSAX Observations of MKN 110
Mkn 110 is a bright, nearby Seyfert 1 galaxy, which underwent a long optical monitoring campaign, during the past 12 years. Optical observations show that Mkn 110 vary, both in flux and spectral shape. The intensity and width of its Broad Emission Lines (BELs) also vary, from typical Seyfert 1, to typical Narrow Line Seyfert 1 (NLSyl) values, so suggesting that this could be the first supermassive black holes where accretion state related transitions, as frequently observed in stellar-size black holes, have finally been observed. To verify these suggestions we asked to monitor Mkn 110 with BeppoSAX with three 50 ksec observations six months apart. The goal of the proposal was to observe spectral variations in X-ray, already suggested by previous, existing ROSAT (Roentgen Satellite) and ASCA (Advanced Satellite for Cosmology and Astrophysics) observations of the same source. The first of these three SAX (Satellite per Astronomia X) observations was taken on May 2000, and lacks the Low-Energy instrument (0.1-2 keV is the band in which NLSy1 and Sy1 X-ray spectra differ most).
Nicastro, Fabrizio↗
The complex X-ray spectra of two high redshift quasars observed with ASCA
We report preliminary results of Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of two high-redshift quasars (zeta approximately 3) PKS 0438-436 and PKS 2126-158. We find spectral flattening towards low energies in both sources, first found with Roentgen Satellite (ROSAT) and interpreted as being due to excess X-ray absorption. However, the ROSAT data lacked the bandpass and sensitivity to unambiguously support this interpretation. We find that for PKS 2126-158, absorption in intervening low-redshift material along the line-of-sight provides a statistically better description of the data than absorption in material intrinsic to the quasar. The redshift of the putative absorber is required to be less than a few tenths. Given the redshift constraints and the fact that absorption is not common in lower redshift quasars, this result is not easily explained by a simple model. Either the absorber may be complex or else the intrinsic X-ray spectrum may be complex, or both. Compton-reflection dominated models are ruled out but a broken power-law model provides good fits to the data without requiring excess absorption. The break energy is at approximately 6-8 keV in the quasar frame and the energy index of the soft component is required to be extremely flat. This may mean that the X-ray emission in these objects is dominated by synchrotron losses as in BL Lac objects.
Serlemitsos, Peter↗
The Anisotropy of the Microwave Background to l=3500: Mosaic Observations with the Cosmic Background Imager
Using the Cosmic Background Imager, a 13-element interferometer array operating in the 26-36 GHz frequency band, we have observed 40 deg (sup 2) of sky in three pairs of fields, each approximately 145 feet x 165 feet, using overlapping pointings: (mosaicing). We present images and power spectra of the cosmic microwave background radiation in these mosaic fields. We remove ground radiation and other low-level contaminating signals by differencing matched observations of the fields in each pair. The primary foreground contamination is due to point sources (radio galaxies and quasars). We have subtracted the strongest sources from the data using higher-resolution measurements, and we have projected out the response to other sources of known position in the power-spectrum analysis. The images show features on scales approximately 6 feet-15 feet, corresponding to masses approximately 5-80 x 10(exp 14) solar mass at the surface of last scattering, which are likely to be the seeds of clusters of galaxies. The power spectrum estimates have a resolution delta l approximately 200 and are consistent with earlier results in the multipole range l approximately less than 1000. The power spectrum is detected with high signal-to-noise ratio in the range 300 approximately less than l approximately less than 1700. For 1700 approximately less than l approximately less than 3000 the observations are consistent with the results from more sensitive CBI deep-field observations. The results agree with the extrapolation of cosmological models fitted to observations at lower l, and show the predicted drop at high l (the "damping tail").
Pearson, T. J.↗
Did Cosmology Trigger the Origin of the Solar System?
It is a matter of curious coincidence that the Solar System formed 4.6 billion years ago around the same epoch that the Friedmann-Lemaitre (FL) universe became -dominated or dark-energy-dominated, where is the cosmological constant. This observation was made in the context of known gravitational anomalies that affect spacecraft orbits during planetary flyby's and the Pioneer anomaly, both possibly having connections with cosmology. In addition, it has been known for some time that the Universe is not only expanding but accelerating as well. Hence one must add the onset of cosmological acceleration in the FL universe as having a possible influence on the origin of the Solar System. These connections will now be examined in greater detail.
Blome, H.-J.↗
The X-ray emission of 3C 273 observed with ASCA
We report preliminary results of an Advanced Satellite for Cosmology and Astrophysics (ASCA) observation of 3C 273. There is no spectral variability within the ASCA observation, in contrast to the longer term behavior found with European X-ray Observatory Satellite (EXOSAT) and Ginga which established significant changes in the spectral index of the power-law continuum on timescales of a week or more, uncorrelated with luminosity. Comparison of the ASCA data with a simultaneous Roentgen Satellite (ROSAT) Ginga observation in 1990 December shows that while the shape of the spectrum above approximately 1 keV is essentially the same, the flux in the soft component, below approximately 1 keV, considerably weaker relative to the hard component in the ASCA observation. The 2-10 keV luminosity is at least a factor of approximately 1.5 greater in the ASCA observation than in the ROSAT/Ginga observation while the ratio of 2-10 keV luminosity to 0.4-1.0 keV luminosity increases by a factor of approximately 1.2. Thus the spectral shape of the hard component appears to be independent of the relative magnitude of the soft component and is an important constraint on emission and reprocessing models. We find no significant Fe K line-emission in this observation. The data also highlight very well some of the outstanding problems in the instrumental responses.
Yaqoob, Tahir↗
The plasma structure of the north-east rim of the Cygnus Loop as observed with ASCA
We present the first results from Advanced Satellite for Cosmology and Astrophysics (ASCAS) observations of the Cygnus Loop. A 22 min square of the north-east rim was observed. The imaging capability of ASCA permits clear indentification of the shock front structure. The energy resolving power of ASCA in the energy band between 0.5 keV to 10 keV reveals several emission lines from oxygen to silicon. The intensity ratio between the O VIII and O VII emission lines demonstrates that the plasma has not reached collisional ionization equilibrium. A nonequilibrium ionization model is applied to determine the gradients both in electron temperature T(sub e), and in electron density n(sub e). T(sub e) ranges from 0.22 keV at the shock front to 0.30 keV at 17 min inside the shock front. n(sub e) can be represented as a power law function of radius with an index of about 6 at an ambient gas density of 0.5 cm(exp -3). The plasma parameter n(sub e)t is about 2 x 10(exp 11) cm(exp -3), resulting in an age of about 20000 yr for the Loop.
Miyata, Emi↗
Dwarf Galaxies at Cosmic Noon: New JWST Constraints on Satellite Models and Subhalo Tidal Evolution
The advent of JWST has revolutionized the study of faint satellite galaxies at z ≳ 1, enabling statistical constraints on galaxy evolution and the galaxy–halo connection in a previously unexplored mass and redshift regime. We compare satellite abundances at 1 < z < 3.5 from recent JWST observations with predictions from cosmological dark-matter-only zoom-in simulations. We identify and quantify several sources of biases that can impact theoretical satellite counts, finding that assumptions about subhalo tidal evolution introduce the largest uncertainty in predictions for the satellite mass function. Using a flexible galaxy disruption model, we explore a range of disruption scenarios, spanning hydrodynamically motivated and idealized prescriptions, to bracket plausible physical outcomes. We show that varying galaxy durability can change the predicted satellite mass functions by a factor of ∼3.5. The JWST data and our fiducial model are consistent within 1σ–2σ across the full redshift (1 < z < 3.5) and stellar mass (M⋆ > 10 7 M ⊙ ) range probed. We find evidence that subhalos are at least as long-lived as predicted by hydrodynamic simulations. Our framework will enable robust constraints on the tidal evolution of subhalos with future observations. This work presents the first direct comparison between cosmological models and observations of the high-redshift satellite population in this low-mass regime. These results showcase JWST’s emerging power to test structure formation in the first half of the Universe in a new domain and to constrain the physical processes driving the evolution of low-mass galaxies across cosmic time.
79 ASTRONOMY AND ASTROPHYSICS↗
The ASCA PV phase observation of FO Aquarii
We report on a approximately 1-day Advanced Satellite for Cosmology and Astrophysics (ASCA) observation of the intermediate polar FO Aquarii. We find two distinctive spectral components, one unabsorbed and the other strongly absorbed; the observed 2-10 keV flux severely underestimates the total system luminosity, due to this strong absorption intrinsic to the binary. The absorbed component is dominant in terms of luminosity, and its light curve is simple. The unabsorbed component accounts for approximately 2% of the luminosity, and shows a much more complicated light curve. As the dominant component predominantly shows a sinusoidal modulation at the white dwarf spin period, it provides a strong evidence for a partial accretion disk in the system.
Mukai, Koji↗
ASCA and Radio/RXTE Observations of GX 339-4
We have analyzed three separate archival Advanced Satellite for Cosmology and Astrophysics (ASCA) observations and eight separate Rossi X-ray Timing Explorer (RXTE) observations of the black hole candidate GX 339-4 in its low luminosity, spectrally hard state. Three of the RXTE observations were strictly simultaneous with 843 MHz and 8.3- 9.1 GHz radio observations. All data sets show evidence for an approximately 6.4 keV Fe line with equivalent widths approximately 20-100 eV. 'Reflection models' show a hardening of the RXTE spectra with decreasing X-ray flux; however, these models do not exhibit evidence of a correlation between the photon index of the incident power law flux and the solid angle subtended by the reflector. None of the models fit to the X-ray data, however, simultaneously explain the observed radio properties. We argue that the spatial extent of the observed radio emission is at least 0(10(exp 7 GM/c squared). Timing analysis reveals that all observations save one show evidence of a persistent f(qpo approximately equals 0.3 Hz quasi-periodic oscillations(quasi-periodic oscillations)). The broad band (10-3-102 Hz) power appears to be dominated by two independent processes that can be modeled as very broad Lorentzians with Q approximately less than 1. Similar to Cyg X-1, the hard photon variability is seen to lag the soft photon vaxiability with the lag time increasing with decreasing Fourier frequency. The magnitude of this time lag is seen to be positively correlated with the flux of GX 339-4.
Nowak, M. A.↗
CLASS Observation of Polarized Cloud Emission at Millimeter Wavelengths
The dynamic atmosphere imposes challenges to ground-based cosmic microwave background observation, especially for measurements on large angular scales. The hydrometeors in the atmosphere, mostly in the form of clouds, scatter the ambient thermal radiation and are known to be the main linearly polarized source in the atmosphere. This scattering-induced polarization is significantly enhanced for ice clouds due to the alignment of ice crystals under gravity, which are also the most common clouds seen at the millimeter-astronomy sites at high altitudes. This work presents a multifrequency study of cloud polarization observed by the Cosmology Large Angular Scale Surveyor experiment on Cerro Toco in the Atacama Desert of northern Chile, from 2016–2022, at the frequency bands centered around 40, 90, 150, and 220 GHz. Using a machine-learning-assisted cloud classifier, we made connections between the transient polarized emission found in all four frequencies with the clouds imaged by monitoring cameras at the observing site. The polarization angles of the cloud events are found to be mostly 90° from the local meridian, which is consistent with the presence of horizontally aligned ice crystals. The90 and 150 GHz polarization data are consistent with a power law with a spectral index of 3.90±0.06, while an excess/deficit of polarization amplitude is found at 40/220 GHz compared with a Rayleigh scattering spectrum. These results are consistent with Rayleigh-scattering-dominated cloud polarization, with possible effects from supercooled water absorption and/or Mie scattering from a population of large cloud particles that contribute to the220 GHz polarization.
Earth's clouds↗
The Linear Point Standard Ruler with DESI DR1 and DR2 Data
The linear point, a purely geometric feature in the monopole of the two-point correlation function, has been proposed as an alternative standard ruler. Compared to the peak in the correlation function, it is more robust to late-time nonlinear effects at the percent level. In light of improved simulations and high quality data, we revisit the robustness of the linear point and use it as an alternative to template-based fitting approaches typically used in BAO analyses. We present the linear point measurements on galaxy samples from the first and second data releases (DR1 and DR2) of the DESI survey. We convert the linear point into a dimensionless parameter $α_{iso,LP}$, defined as the ratio of the linear point in the fiducial cosmology and the observed value, analogous to the isotropic BAO scaling parameter $α_{iso}$ used in previous BAO measurements. Using the 2nd generation of AbacusSummit mock catalogs, we find that linear point measurements are more precise when calculated in the post-reconstruction regime with 15-60% smaller uncertainties than those pre-reconstruction. We find a systematic shift in the linear point measurements compared against the isotropic BAO measurements in mocks; we attribute this to the isotropic damping parameter responsible for smearing the linear point in the nonlinear regime. We propose a sample-dependent correction that mitigates the impact of late-time nonlinear effects. While this introduces a cosmology dependence in an otherwise model-independent measurement, this is necessary given the sub-percent precision dictated by current cosmological surveys. Comparing $α_{iso,LP}$ with isotropic BAO measurements made on the DESI DR1 and DR2 galaxy samples, we find excellent agreement after applying this correction, particularly post-reconstruction. We discuss future scope regarding cosmological inference with linear point measurements.
Uberoi, N. [Yale U.] (ORCID:0000000275179629)↗
The effects of pure density evolution on the brightness distribution of cosmological gamma-ray bursts
In this work, we explore the effects of burst rate density evolution on the observed brightness distribution of cosmological gamma-ray bursts. Although the brightness distribution of gamma-ray bursts observed by the BATSE experiment has been shown to be consistent with a nonevolving source population observed to redshifts of order unity, evolution of some form is likely to be present in the gamma-ray bursts. Additionally, nonevolving models place significant constraints on the range of observed burst luminosities, which are relaxed if evolution of the burst population is present. In this paper, three analytic forms of density evolution are examined. In general, forms of evolution with densities that increase monotonically with redshift require that the BATSE data correspond to bursts at larger redshifts, or to incorporate a wider range of burst luminosities, or both. Independent estimates of the maximum observed redshift in the BATSE data and/or the range of luminosity from which a large fraction of the observed bursts are drawn therefore allow for constraints to be placed on the amount of evolution that may be present in the burst population. Specifically, if recent measurements obtained from analysis of the BATSE duration distribution of the actual limiting redshift in the BATSE data at z(sub lim) = 2 are correct, the BATSE N(P) distribution in a Lambda = 0 universe is inconsistent at a level of approximately 3 alpha with nonevolving gamma-ray bursts and some form of evolution in the population is required. The sense of this required source evolution is to provide a higher density, larger luminosities, or both with increasing redshift.
Horack, J. M.↗