scholarly journals The Atacama Cosmology Telescope: two-season ACTPol extragalactic point sources and their polarization properties

2018 ◽  
Vol 486 (4) ◽  
pp. 5239-5262 ◽  
Author(s):  
Rahul Datta ◽  
Simone Aiola ◽  
Steve K Choi ◽  
Mark Devlin ◽  
Joanna Dunkley ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Detection Threshold ◽  
Polarization Measurement ◽  
Point Sources ◽  
Total Flux ◽  
Spectral Energy ◽  
Source Population ◽  
Microwave Background ◽  
Atacama Cosmology Telescope ◽  
Celestial Equator

ABSTRACT We report on measurements of the polarization of extragalactic sources at 148 GHz made during the first two seasons of the Atacama Cosmology Telescope Polarization (ACTPol) survey. The survey covered 680 deg2 of the sky on the celestial equator. Polarization measurements of 169 intensity-selected sources brighter than 30 mJy, that are predominantly active galactic nuclei, are presented. Above a total flux of 215 mJy where the noise bias removal in the polarization measurement is reliable, we detect 26 sources, 14 of which have a detection of linear polarization at greater than 3σ significance. The distribution of the fractional polarization as a function of total source intensity is analysed. Our result is consistent with the scenario that the fractional polarization of our measured radio source population is independent of total intensity down to the limits of our measurements and well described by a Gaussian distribution with a mean fractional polarization pm = 0.028 ± 0.005 and standard deviation $\sigma _{\mathrm{p_{m}}}$ = 0.054, truncated at p = 0. Extrapolating this model for the distribution of source polarization below the ACTPol detection threshold, we predict that one could get a clean measure of the E-mode polarization power spectrum of the microwave background out to $\ell \approx 6000$ with 1 $\mu$K-arcminute maps over ${10\!{\ \rm \%}}$ of the sky from a future survey. We also study the spectral energy distribution of the total and polarized source flux densities by cross-matching with low radio frequency catalogues. We do not find any correlation between the spectral indices for total flux and polarized flux.

scholarly journals Accretion and Outflow Activity in the Earliest Phases of Star-Formation: CO, Sub-mm Continuum, and Near-Infrared Observations

1997 ◽  
Vol 163 ◽  
pp. 725-726
Author(s):  
K.-W. Hodapp ◽  
E. F. Ladd
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Point Sources ◽  
Spectral Energy ◽  
Infrared Observations ◽  
Circumstellar Material ◽  
Dense Cores ◽  
Wavelength Radiation ◽  
Main Component

Stars in the earliest phases of their formation, i.e., those accreting the main component of their final mass, are deeply embedded within dense cores of dust and molecular material. Because of the high line-of-sight extinction and the large amount of circumstellar material, stellar emission is reprocessed by dust into long wavelength radiation, typically in the far-infrared and sub-millimeter bands. Consequently, the youngest sources are strong submillimeter continuum sources, and often undetectable as point sources in the near-infrared and optical. The most deeply embedded of these sources have been labelled “Class 0” sources by André, Ward-Thompson, & Barsony (1994), in an extension of the spectral energy distribution classification scheme first proposed by Adams, Lada, & Shu (1987).

scholarly journals Systematic effects in LOFAR data: A unified calibration strategy

2019 ◽  
Vol 622 ◽  
pp. A5 ◽  
Author(s):  
F. de Gasperin ◽  
T. J. Dijkema ◽  
A. Drabent ◽  
M. Mevius ◽  
D. Rafferty ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Low Frequency ◽  
Reduction Process ◽  
Spectral Energy ◽  
Ionospheric Scintillation ◽  
Source Population ◽  
Full Data ◽  
Low Frequencies ◽  
Beam Shape ◽  
Systematic Effects

Context. New generation low-frequency telescopes are exploring a new parameter space in terms of depth and resolution. The data taken with these interferometers, for example with the LOw Frequency ARray (LOFAR), are often calibrated in a low signal-to-noise ratio regime and the removal of critical systematic effects is challenging. The process requires an understanding of their origin and properties. Aim. In this paper we describe the major systematic effects inherent to next generation low-frequency telescopes, such as LOFAR. With this knowledge, we introduce a data processing pipeline that is able to isolate and correct these systematic effects. The pipeline will be used to calibrate calibrator observations as the first step of a full data reduction process. Methods. We processed two LOFAR observations of the calibrator 3C 196: the first using the Low Band Antenna (LBA) system at 42–66 MHz and the second using the High Band Antenna (HBA) system at 115–189 MHz. Results. We were able to isolate and correct for the effects of clock drift, polarisation misalignment, ionospheric delay, Faraday rotation, ionospheric scintillation, beam shape, and bandpass. The designed calibration strategy produced the deepest image to date at 54 MHz. The image has been used to confirm that the spectral energy distribution of the average radio source population tends to flatten at low frequencies. Conclusions. We prove that LOFAR systematic effects can be described by a relatively small number of parameters. Furthermore, the identification of these parameters is fundamental to reducing the degrees of freedom when the calibration is carried out on fields that are not dominated by a strong calibrator.

scholarly journals The polarized spectral energy distribution of NGC 4151

2020 ◽  
Vol 496 (1) ◽  
pp. 215-222
Author(s):  
F Marin ◽  
J Le Cam ◽  
E Lopez-Rodriguez ◽  
M Kolehmainen ◽  
B L Babler ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Far Infrared ◽  
Seyfert Galaxies ◽  
Mie Scattering ◽  
Polarization Measurement ◽  
Spectral Energy ◽  
Ngc 4151 ◽  
Near Ir

ABSTRACT NGC 4151 is among the most well-studied Seyfert galaxies that does not suffer from strong obscuration along the observer’s line of sight. This allows to probe the central active galactic nucleus (AGN) engine with photometry, spectroscopy, reverberation mapping, or interferometry. Yet, the broad-band polarization from NGC 4151 has been poorly examined in the past despite the fact that polarimetry gives us a much cleaner view of the AGN physics than photometry or spectroscopy alone. In this paper, we compile the 0.15–89.0 μm total and polarized fluxes of NGC 4151 from archival and new data in order to examine the physical processes at work in the heart of this AGN. We demonstrate that, from the optical to the near-infrared (IR) band, the polarized spectrum of NGC 4151 shows a much bluer power-law spectral index than that of the total flux, corroborating the presence of an optically thick, locally heated accretion flow, at least in its near-IR emitting radii. Specific signatures from the atmosphere of the accretion structure are tentatively found at the shortest ultraviolet (UV) wavelengths, before the onset of absorption opacity. Otherwise, dust scattering appears to be the dominant contributor from the near-UV to near-IR polarized spectrum, superimposed on to a weaker electron component. We also identify a change in the polarization processes from the near-IR to the mid-IR, most likely associated with the transition from Mie scattering to dichroic absorption from aligned dust grains in the dusty torus or narrow-line region. Finally, we present and discuss the very first far-infrared polarization measurement of NGC 4151 at 89 μm.

scholarly journals S–PASS view of polarized Galactic synchrotron at 2.3 GHz as a contaminant to CMB observations

2018 ◽  
Vol 618 ◽  
pp. A166 ◽  
Author(s):  
N. Krachmalnicoff ◽  
E. Carretti ◽  
C. Baccigalupi ◽  
G. Bernardi ◽  
S. Brown ◽  
...  
Keyword(s):  
Power Law ◽  
Spectral Energy Distribution ◽  
Power Spectra ◽  
Low Frequency ◽  
Spectral Amplitude ◽  
Spectral Energy ◽  
Harmonic Space ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Sky Survey

We have analyzed the southern sky emission in linear polarization at 2.3 GHz as observed by the S -band Polarization All Sky Survey (S-PASS). Our purpose is to study the properties of the diffuse Galactic polarized synchrotron as a contaminant to B-mode observations of the cosmic microwave background (CMB) polarization. We studied the angular distribution of the S-PASS signal at intermediate and high Galactic latitudes by means of the polarization angular power spectra. The power spectra, computed in the multipole interval 20 ≤ ℓ ≤ 1000, show a decay of the spectral amplitude as a function of multipole for ℓ ≲ 200, typical of the diffuse emission. At smaller angular scales, power spectra are dominated by the radio point source radiation. We find that, at low multipoles, spectra can be approximated by a power law CℓEE,BB ∝ ℓα, with α ≃ −3, and characterized by a B-to-E ratio of about 0.5. We measured the polarized synchrotron spectral energy distribution (SED) in harmonic space, by combining S-PASS power spectra with low frequency WMAP and Planck ones, and by fitting their frequency dependence in six multipole bins, in the range 20 ≤ ℓ ≤ 140. Results show that the recovered SED, in the frequency range 2.3–33 GHz, is compatible with a power law with βs = −3.22 ± 0.08, which appears to be constant over the considered multipole range and in the different Galactic cuts. Combining the S-PASS total polarized intensity maps with those coming from WMAP and Planck we derived a map of the synchrotron spectral index βs at angular resolution of 2° on about 30% of the sky. The recovered βs distribution peaks at the value around −3.2. It exibits an angular power spectrum which can be approximated with a power law Cℓ ∝ ℓγ with γ ≃ −2.6. We also measured a significant spatial correlation between synchrotron and thermal dust signals, as traced by the Planck 353 GHz channel. This correlation reaches about 40% on the larger angular scales, decaying considerably at the degree scales. Finally, we used the S-PASS maps to assess the polarized synchrotron contamination to CMB observations of the B-modes at higher frequencies. We divided the sky in small patches (with fsky ≃ 1%) and find that, at 90 GHz, the minimal contamination, in the cleanest regions of the sky, is at the level of an equivalent tensor-to-scalar ratio rsynch ≃ 10−3. Moreover, by combining S-PASS data with Planck 353 GHz observations, we recover a map of the minimum level of total polarized foreground contamination to B-modes, finding that there is no region of the sky, at any frequency, where this contamination lies below equivalent tenor-to-scalar ratio rFG ≃ 10−3. This result confirms the importance of observing both high and low frequency foregrounds in CMB B-mode measurements.

scholarly journals Planck intermediate results

2017 ◽  
Vol 599 ◽  
pp. A51 ◽  
Author(s):  
◽  
N. Aghanim ◽  
M. Ashdown ◽  
J. Aumont ◽  
C. Baccigalupi ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Dust Emission ◽  
Power Spectra ◽  
Spectral Energy ◽  
Polarization Angle ◽  
Galactic Latitude ◽  
Correlation Ratio ◽  
Microwave Background

The characterization of the Galactic foregrounds has been shown to be the main obstacle in thechallenging quest to detect primordial B-modes in the polarized microwave sky. We make use of the Planck-HFI 2015 data release at high frequencies to place new constraints on the properties of the polarized thermal dust emission at high Galactic latitudes. Here, we specifically study the spatial variability of the dust polarized spectral energy distribution (SED), and its potential impact on the determination of the tensor-to-scalar ratio, r. We use the correlation ratio of the CBBℓ angular power spectra between the 217 and 353 GHz channels as a tracer of these potential variations, computed on different high Galactic latitude regions, ranging from 80% to 20% of the sky. The new insight from Planck data is a departure of the correlation ratio from unity that cannot be attributed to a spurious decorrelation due to the cosmic microwave background, instrumental noise, or instrumental systematics. The effect is marginally detected on each region, but the statistical combination of all the regions gives more than 99% confidence for this variation in polarized dust properties. In addition, we show that the decorrelation increases when there is a decrease in the mean column density of the region of the sky being considered, and we propose a simple power-law empirical model for this dependence, which matches what is seen in the Planck data. We explore the effect that this measured decorrelation has on simulations of the BICEP2-Keck Array/Planck analysis and show that the 2015 constraints from these data still allow a decorrelation between the dust at 150 and 353 GHz that is compatible with our measured value. Finally, using simplified models, we show that either spatial variation of the dust SED or of the dust polarization angle are able to produce decorrelations between 217 and 353 GHz data similar to the values we observe in the data.

scholarly journals The molecular cloud and embedded young stellar population associated with IRAS 18236–1205

2009 ◽  
Vol 5 (S266) ◽  
pp. 516-516
Author(s):  
Ricardo Retes ◽  
Abraham Luna ◽  
Divakara Mayya ◽  
Luis Carrasco
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Massive Star ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Point Sources ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Massive Star Formation ◽  
Iras Source

AbstractWe test a membership method to select embedded young stellar objects (YSOs) from a Galactic molecular cloud with ongoing massive star formation using multiband analysis. We select and discuss the embedded stellar population in the molecular cloud associated with IRAS 18235−1205, a small, geometrically well-defined Galactic molecular cloud. The IRAS source has infrared fluxes characteristic of an UCHii region, CS(J = 2 − 1) emission, and methanol and water maser emission, suggesting that this region is a good candidate for studies of young, massive star formation. The selection method of embedded stellar populations is based on the spatial distribution of 13CO(J = 1 − 0) and Spitzer/MIPS 24 μm point sources. Photometric analysis using near/mid-infrared images are used to test our selection criteria. Three objects are associated with the IRAS source; two have a characteristic spectral-energy distribution (SED) of a Class I/0 object (protostar) and the third has an SED of Class II.

scholarly journals Extended X-ray emission from the z = 4.26 radio galaxy 4C 63.20

2020 ◽  
Vol 498 (2) ◽  
pp. 1550-1559
Author(s):  
Kate Napier ◽  
Adi Foord ◽  
Elena Gallo ◽  
Gabriele Ghisellini ◽  
Edmund Hodges-Kluck ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Radio Galaxies ◽  
Spectral Energy ◽  
Synchrotron Emission ◽  
Radio Flux ◽  
Microwave Background ◽  
X Ray ◽  
Inverse Compton

ABSTRACT We report on deep Chandra X-ray Telescope imaging observations of 4C 63.20, one of the few known radio galaxies at z > 3.5. The X-ray counterpart is resolved into a core plus two off-nuclear sources that (combined) account for close to 30 per cent of the total X-ray flux. Their morphology and orientation are consistent with a diffuse, lobe-like nature, albeit compact hotspots cannot be ruled out. The broad-band spectral energy distribution of 4C 63.20 can be reproduced with a jet model where the majority of the radio flux can be ascribed to synchrotron emission from the hotspots, whereas the (non-nuclear) X-ray emission is produced via inverse Compton (IC) off of cosmic microwave background (CMB) photons within the extended lobes. This scenario is broadly consistent with the expectation from highly magnetized lobes in a hotter CMB, and supports the view that IC/CMB may quench less extreme radio lobes at high redshifts.

scholarly journals Central X-Ray Point Sources Found to Be Abundant in Low-mass, Late-type Galaxies Predicted to Contain an Intermediate-mass Black Hole

2021 ◽  
Vol 923 (2) ◽  
pp. 246
Author(s):  
Alister W. Graham ◽  
Roberto Soria ◽  
Benjamin L. Davis ◽  
Mari Kolehmainen ◽  
Thomas Maccarone ◽  
...  
Keyword(s):  
Black Hole ◽  
Spectral Energy Distribution ◽  
Star Clusters ◽  
Virgo Cluster ◽  
Point Sources ◽  
Spectral Energy ◽  
Late Type ◽  
Intermediate Mass ◽  
X Ray ◽  
X Ray Binaries

Abstract Building upon three late-type galaxies in the Virgo cluster with both a predicted black hole mass of less than ∼105 M ⊙ and a centrally located X-ray point source, we reveal 11 more such galaxies, more than tripling the number of active intermediate-mass black hole candidates among this population. Moreover, this amounts to a ∼36 ± 8% X-ray detection rate (despite the sometimes high, X-ray-absorbing, H i column densities), compared to just 10 ± 5% for (the largely H i-free) dwarf early-type galaxies in the Virgo cluster. The expected contribution of X-ray binaries from the galaxies’ inner field stars is negligible. Moreover, given that both the spiral and dwarf galaxies contain nuclear star clusters, the above inequality appears to disfavor X-ray binaries in nuclear star clusters. The higher occupation, or rather detection, fraction among the spiral galaxies may instead reflect an enhanced cool gas/fuel supply and Eddington ratio. Indeed, four of the 11 new X-ray detections are associated with known LINERs or LINER/H ii composites. For all (four) of the new detections for which the X-ray flux was strong enough to establish the spectral energy distribution in the Chandra band, it is consistent with power-law spectra. Furthermore, the X-ray emission from the source with the highest flux (NGC 4197: L X ≈ 1040 erg s−1) suggests a non-stellar-mass black hole if the X-ray spectrum corresponds to the “low/hard state”. Follow-up observations to further probe the black hole masses, and prospects for spatially resolving the gravitational spheres of influence around intermediate-mass black holes, are reviewed in some detail.

scholarly journals Galactic Foreground Constraints on Primordial B-mode Detection for Ground-based Experiments

2022 ◽  
Vol 924 (1) ◽  
pp. 11
Author(s):  
Carlos Hervías-Caimapo ◽  
Anna Bonaldi ◽  
Michael L. Brown ◽  
Kevin M. Huffenberger
Keyword(s):  
Fisher Information Matrix ◽  
Spectral Energy Distribution ◽  
Information Matrix ◽  
Component Separation ◽  
Spectral Energy ◽  
Noise Levels ◽  
Microwave Background ◽  
Mode Detection ◽  
Error Bar ◽  
Component Separation Method

Abstract Contamination by polarized foregrounds is one of the biggest challenges for future polarized cosmic microwave background (CMB) surveys and the potential detection of primordial B-modes. Future experiments, such as Simons Observatory (SO) and CMB-S4, will aim at very deep observations in relatively small (f sky ∼ 0.1) areas of the sky. In this work, we investigate the forecasted performance, as a function of the survey field location on the sky, for regions over the full sky, balancing between polarized foreground avoidance and foreground component separation modeling needs. To do this, we simulate observations by an SO-like experiment and measure the error bar on the detection of the tensor-to-scalar ratio, σ(r), with a pipeline that includes a parametric component separation method, the Correlated Component Analysis, and the use of the Fisher information matrix. We forecast the performance over 192 survey areas covering the full sky and also for optimized low-foreground regions. We find that modeling the spectral energy distribution of foregrounds is the most important factor, and any mismatch will result in residuals and bias in the primordial B-modes. At these noise levels, σ(r) is not especially sensitive to the level of foreground contamination, provided the survey targets the least-contaminated regions of the sky close to the Galactic poles.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A16 ◽  
Author(s):  
Andrew Butler ◽  
Minh Huynh ◽  
Ivan Delvecchio ◽  
Anna Kapińska ◽  
Paolo Ciliegi ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Optical Emission ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Radio Sources ◽  
Source Population ◽  
Host Galaxies ◽  
X Ray

The classification of the host galaxies of the radio sources in the 25 deg2 ultimate XMM extragalactic survey south field (XXL-S) is presented. XXL-S was surveyed at 2.1 GHz with the Australia Telescope Compact Array (ATCA) and is thus far the largest area radio survey conducted down to rms flux densities of σ ~ 41 μJy beam−1. Of the 6287 radio sources in XXL-S, 4758 (75.7%) were cross-matched to an optical counterpart using the likelihood ratio technique. There are 1110 spectroscopic redshifts and 3648 photometric redshifts available for the counterparts, of which 99.4% exist out to z ~ 4. A number of multiwavelength diagnostics, including X-ray luminosities, mid-infrared colours, spectral energy distribution fits, radio luminosities, and optical emission lines and colours, were used to classify the sources into three types: low-excitation radio galaxies (LERGs), high-excitation radio galaxies (HERGs), and star-forming galaxies (SFGs). The final sample contains 1729 LERGs (36.3%), 1159 radio-loud HERGs (24.4%), 296 radio-quiet HERGs (6.2%), 558 SFGs (11.7%), and 1016 unclassified sources (21.4%). The XXL-S sub-mJy radio source population is composed of ~75% active galactic nuclei and ~20% SFGs down to 0.2 mJy. The host galaxy properties of the HERGs in XXL-S are independent of the HERG selection, but the XXL-S LERG and SFG selection is, due to the low spectral coverage, largely determined by the known properties of those populations. Considering this caveat, the LERGs tend to exist in the most massive galaxies with low star formation rates and redder colours, whereas the HERGs and SFGs exist in galaxies of lower mass, higher star formation rates, and bluer colours. The fraction of blue host galaxies is higher for radio-quiet HERGs than for radio-loud HERGs. LERGs and radio-loud HERGs are found at all radio luminosities, but radio-loud HERGs tend to be more radio luminous than LERGs at a given redshift. These results are consistent with the emerging picture in which LERGs exist in the most massive quiescent galaxies typically found in clusters with hot X-ray halos and HERGs are associated with ongoing star formation in their host galaxies via the accretion of cold gas.

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