scholarly journals Multiwavelength consensus of large-scale linear bias

2020 ◽  
Vol 493 (1) ◽  
pp. 747-764 ◽  
Author(s):  
Hengxing Pan ◽  
Danail Obreschkow ◽  
Cullan Howlett ◽  
Claudia del P Lagos ◽  
Pascal J Elahi ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Broad Band ◽  
Far Infrared ◽  
Absolute Magnitude ◽  
Emission Lines ◽  
Continuum Emission ◽  
Star Forming ◽  
Galaxy Bias ◽  
The Continuum

ABSTRACT We model the large-scale linear galaxy bias bg(x, z) as a function of redshift z and observed absolute magnitude threshold x for broad-band continuum emission from the far-infrared to ultraviolet, as well as for prominent emission lines, such as the H α, H β, Ly a, and [O ii] lines. The modelling relies on the semi-analytic galaxy formation model galform, run on the state-of-the-art N-body simulation surfs with the Planck 2015 cosmology. We find that both the differential bias at observed absolute magnitude x and the cumulative bias for magnitudes brighter than x can be fitted with a five-parameter model: bg(x, z) = a + b(1 + z)e(1 + exp [(x − c)d]). We also find that the bias for the continuum bands follows a very similar form regardless of wavelength due to the mixing of star-forming and quiescent galaxies in a magnitude-limited survey. Differences in bias only become apparent when an additional colour separation is included, which suggest extensions to this work could look at different colours at fixed magnitude limits. We test our fitting formula against observations, finding reasonable agreement with some measurements within 1σ statistical uncertainties, and highlighting areas of improvement. We provide the fitting parameters for various continuum bands, emission lines, and intrinsic galaxy properties, enabling a quick estimation of the linear bias in any typical survey of large-scale structure.

scholarly journals Mapping large-scale-structure evolution over cosmic times

2021 ◽  
Author(s):  
Marta B. Silva ◽  
Ely D. Kovetz ◽  
Garrett K. Keating ◽  
Azadeh Moradinezhad Dizgah ◽  
Matthieu Bethermin ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
High Redshift ◽  
Formation Rate ◽  
Far Infrared ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Structure Evolution ◽  
Intensity Mapping ◽  
Wide Range

AbstractThis paper outlines the science case for line-intensity mapping with a space-borne instrument targeting the sub-millimeter (microwaves) to the far-infrared (FIR) wavelength range. Our goal is to observe and characterize the large-scale structure in the Universe from present times to the high redshift Epoch of Reionization. This is essential to constrain the cosmology of our Universe and form a better understanding of various mechanisms that drive galaxy formation and evolution. The proposed frequency range would make it possible to probe important metal cooling lines such as [CII] up to very high redshift as well as a large number of rotational lines of the CO molecule. These can be used to trace molecular gas and dust evolution and constrain the buildup in both the cosmic star formation rate density and the cosmic infrared background (CIB). Moreover, surveys at the highest frequencies will detect FIR lines which are used as diagnostics of galaxies and AGN. Tomography of these lines over a wide redshift range will enable invaluable measurements of the cosmic expansion history at epochs inaccessible to other methods, competitive constraints on the parameters of the standard model of cosmology, and numerous tests of dark matter, dark energy, modified gravity and inflation. To reach these goals, large-scale structure must be mapped over a wide range in frequency to trace its time evolution and the surveyed area needs to be very large to beat cosmic variance. Only a space-borne mission can properly meet these requirements.

scholarly journals Evolution and State of the Local ISM

1996 ◽  
Vol 171 ◽  
pp. 442-442
Author(s):  
T. Schmutzler ◽  
D. Breitschwerdt
Keyword(s):  
Basic Feature ◽  
Emission Lines ◽  
Continuum Emission ◽  
Ionization Equilibrium ◽  
X Ray ◽  
Self Consistent ◽  
X Ray Background ◽  
Collisional Ionization ◽  
Consistent Approach ◽  
The Continuum

The most puzzling observations concerning the LISM (distance < 100 pc) can be explained by a fast adiabatically cooled gas in the cavity of an old superbubble. The ultrasoft X-ray background and contributions to the C- and M-bands are due to the continuum emission of delayed recombination [1]. In contrast to collisional ionization equilibrium (CIE) models, but consistent with recent observations [2], our model predicts a lack of emission lines and a low emissivity in the EUV range. In the figure below we compare the emissivities resulting from CIE at T = 106 K and those from our model at T = 4.2 × 104 K. The basic feature of our model is a thermally self-consistent approach of the time-dependent evolution.

scholarly journals Ultraviolet emission line imaging of planetary nebulae with GALEX

2011 ◽  
Vol 7 (S283) ◽  
pp. 308-309 ◽  
Author(s):  
Luciana Bianchi ◽  
Arturo Manchado ◽  
Karl Forster
Keyword(s):  
Galaxy Evolution ◽  
Broad Band ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Continuum Emission ◽  
Ultraviolet Emission ◽  
The Galaxy ◽  
Optical Domain ◽  
Line Imaging ◽  
Shock Fronts

AbstractGALEX (the Galaxy Evolution Explorer) has provided far-UV(1344-1786Å) and near-UV(1771-2831Å) imaging of several Planetary Nebulae (e.g., Bianchi et al. 2008, Bianchi 2012), with flux limits ~27.5 mag/sq.arcsec for objects in the Medium-deph Imaging Survey (MIS). PNe images in the GALEX broad-band UV filters include flux from both nebular line and continuum emission. We use the GALEX grism observing mode to obtain slitless spectral imaging of a sample of PNe with diameters >1′, in the near-UV. We show the first data from this program. The grism produces 2D images of the prominent UV nebular emission lines, when such lines dominate the flux. Combined with monochromatic images of diagnostic lines in the optical domain, such data help detect and interpret ionization and shock fronts, especially in faint nebular regions.

scholarly journals Observations of Solar Continuum Emission at Decameter Wavelengths

1990 ◽  
Vol 142 ◽  
pp. 513-514
Author(s):  
Ch. V. Sastry
Keyword(s):  
Electron Temperature ◽  
Brightness Temperature ◽  
Large Scale ◽  
Continuum Emission ◽  
The Sun ◽  
Temperature Variations ◽  
One Dimensional ◽  
Wave Radio ◽  
Grating Interferometer ◽  
The Continuum

We observed the continuum emission from the radio sun when there is no burst activity at λ = 8.7 m with the large decameter wave radio telescope at Gauribidanur (Latitude 13° 36‘ 12“ N and 77° 27‘ 07“ E) with a resolution of 26'/40'. A compound grating interferometer with one dimensional resolution of 3' is also used. These observations are made during August 1983 and June 1986. The brightness temperature at the center of the sun varied from 0.2 106 K to 0.8 106 K during these periods on time scales of several hours to a day. Since the sun is absolutely quiet during these periods we believe that the radiation is purely thermal in nature. In this case the observed brightness temperature variations imply large scale density variations by more than a factor of three if the corona is optically thin at these wavelengths. Alternatively if the corona is optically thick the observations imply real electron temperature variations with or without accompanying density variations.

scholarly journals High resolution observations of molecular emission lines toward the CI Tau proto-planetary disc: planet-carved gaps or shadowing?

2020 ◽  
Author(s):  
Giovanni P Rosotti ◽  
John D Ilee ◽  
Stefano Facchini ◽  
Marco Tazzari ◽  
Richard A Booth ◽  
...  
Keyword(s):  
High Resolution ◽  
Surface Density ◽  
Morphological Study ◽  
Emission Lines ◽  
Continuum Emission ◽  
Gas Emission ◽  
The Third ◽  
Chemical Effects ◽  
Transfer Modelling ◽  
The Continuum

Abstract Recent observations have revealed that most proto-planetary discs show a pattern of bright rings and dark gaps. However, most of the high-resolution observations have focused only on the continuum emission. In this Paper we present high-resolution ALMA band 7 (0.89mm) observations of the disc around the star CI Tau in the 12CO & 13CO J = 3–2 and CS J = 7–6 emission lines. Our recent work demonstrated that the disc around CI Tau contains three gaps and rings in continuum emission, and we look for their counterparts in the gas emission. While we find no counterpart of the third gap and ring in 13CO, the disc has a gap in emission at the location of the second continuum ring (rather than gap). We demonstrate that this is mostly an artefact of the continuum subtraction, although a residual gap still remains after accounting for this effect. Through radiative transfer modelling we propose this is due to the inner disc shadowing the outer parts of the disc and making them colder. This raises a note of caution in mapping high-resolution gas emission lines observations to the gas surface density – while possible, this needs to be done carefully. In contrast to 13CO, CS emission shows instead a ring morphology, most likely due to chemical effects. Finally, we note that 12CO is heavily absorbed by the foreground preventing any morphological study using this line.

scholarly journals Resolving a dusty, star-forming SHiZELS galaxy at z = 2.2 with HST, ALMA and SINFONI on kiloparsec scales

2021 ◽  
Author(s):  
R K Cochrane ◽  
P N Best ◽  
I Smail ◽  
E Ibar ◽  
C Cheng ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Rest Frame ◽  
Far Infrared ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Star Forming ◽  
Alpha Emission ◽  
The Galaxy ◽  
Dust Distribution

Abstract We present ∼0.15″ spatial resolution imaging of SHiZELS-14, a massive ($M_{*}\sim 10^{11}\, \rm {M_{\odot }}$), dusty, star-forming galaxy at z = 2.24. Our rest-frame $\sim 1\, \rm {kpc}$-scale, matched-resolution data comprise four different widely used tracers of star formation: the $\rm {H}\alpha$ emission line (from SINFONI/VLT), rest-frame UV continuum (from HST F606W imaging), the rest-frame far-infrared (from ALMA), and the radio continuum (from JVLA). Although originally identified by its modest $\rm {H}\alpha$ emission line flux, SHiZELS-14 appears to be a vigorously star-forming ($\rm {SFR}\sim 1000\, \rm {M_{\odot }\, yr^{-1}}$) example of a submillimeter galaxy, probably undergoing a merger. SHiZELS-14 displays a compact, dusty central starburst, as well as extended emission in $\rm {H}\alpha$ and the rest-frame optical and FIR. The UV emission is spatially offset from the peak of the dust continuum emission, and appears to trace holes in the dust distribution. We find that the dust attenuation varies across the spatial extent of the galaxy, reaching a peak of at least AHα ∼ 5 in the most dusty regions, although the extinction in the central starburst is likely to be much higher. Global star-formation rates inferred using standard calibrations for the different tracers vary from $\sim 10\!-\!1000\, \rm {M_{\odot }\, yr^{-1}}$, and are particularly discrepant in the galaxy’s dusty centre. This galaxy highlights the biased view of the evolution of star-forming galaxies provided by shorter wavelength data.

scholarly journals A Model of the Broad-Band Continuum of NGC 5548

1998 ◽  
Vol 188 ◽  
pp. 430-431
Author(s):  
P. Magdziarz ◽  
O. Blaes
Keyword(s):  
Broad Band ◽  
Continuum Emission ◽  
Band Spectrum ◽  
Complex Phase ◽  
Disk Structure ◽  
Three Phase ◽  
Central Disk ◽  
Ngc 5548 ◽  
Excess Component ◽  
The Continuum

We discuss a model of the central source in Seyfert 1 galaxy NGC 5548. The model assumes a three phase disk structure consisting of a cold outer disk, a hot central disk constituting a Comptonizing X/γ source, and an intermediate unstable and complex phase emitting a soft excess component. The model qualitatively explains broad-band spectrum and variability behavior assuming that the soft excess contributes significantly to the continuum emission and drives variability by geometrical changes of the intermediate disk zone.

scholarly journals Understanding galaxy formation and evolution through an all-sky submillimetre spectroscopic survey

2020 ◽  
Vol 37 ◽  
Author(s):  
Mattia Negrello ◽  
Matteo Bonato ◽  
Zhen-Yi Cai ◽  
Helmut Dannerbauer ◽  
Gianfranco De Zotti ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Cluster Formation ◽  
Three Dimensional ◽  
Galaxy Cluster ◽  
Far Infrared ◽  
Space Telescope ◽  
Star Forming ◽  
Quantum Leap ◽  
The Universe

Abstract We illustrate the extraordinary discovery potential for extragalactic astrophysics of a far-infrared/submillimetre (far-IR/submm) all-sky spectroscopic survey with a 3-m-class space telescope. Spectroscopy provides a three-dimensional view of the Universe and allows us to take full advantage of the sensitivity of present-day instrumentation, close to fundamental limits, overcoming the spatial confusion that affects broadband far-IR/submm surveys. A space telescope of the 3-m class (which has already been described in recent papers) will detect emission lines powered by star formation in galaxies out to $z\,{\simeq}\,8$ . It will specifically provide measurements of spectroscopic redshifts, star-formation rates (SFRs), dust masses, and metal content for millions of galaxies at the peak epoch of cosmic star formation and of hundreds of them at the epoch of reionisation. Many of these star-forming galaxies will be strongly lensed; the brightness amplification and stretching of their sizes will make it possible to investigate (by means of follow-up observations with high-resolution instruments like ALMA, JWST, and SKA) their internal structure and dynamics on the scales of giant molecular clouds (40–100 pc). This will provide direct information on the physics driving the evolution of star-forming galaxies. Furthermore, the arcmin resolution of the telescope at submm wavelengths is ideal for detecting the cores of galaxy proto-clusters, out to the epoch of reionisation. Due to the integrated emission of member galaxies, such objects (as well as strongly lensed sources) will dominate at the highest apparent far-IR luminosities. Tens of millions of these galaxy-clusters-in-formation will be detected at $z \simeq 2 - 3$ –3, with a tail extending out to $z\,{\simeq}\,7$ , and thousands of detections at $6\,{<}\,z\,{<}\,7$ . Their study will allow us to track the growth of the most massive halos well beyond what is possible with classical cluster surveys (mostly limited to $z\,\lesssim\, 1.5 - 2$ –2), tracing the history of star formation in dense environments and teaching us how star formation and galaxy-cluster formation are related across all epochs. The obscured cosmic SFR density of the Universe will thereby be constrained. Such a survey will overcome the current lack of spectroscopic redshifts of dusty star-forming galaxies and galaxy proto-clusters, representing a quantum leap in far-IR/submm extragalactic astrophysics.

scholarly journals The AGN contribution to the UV–FIR luminosities of interacting galaxies and its role in identifying the main sequence

2020 ◽  
Vol 499 (3) ◽  
pp. 4325-4369
Author(s):  
Andrés F Ramos Padilla ◽  
M L N Ashby ◽  
Howard A Smith ◽  
Juan R Martínez-Galarza ◽  
Aliza G Beverage ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Far Infrared ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Star Forming ◽  
Nuclear Regions ◽  
The Impact

ABSTRACT Emission from active galactic nuclei (AGNs) is known to play an important role in the evolution of many galaxies including luminous and ultraluminous systems (U/LIRGs), as well as merging systems. However, the extent, duration, and exact effects of its influence are still imperfectly understood. To assess the impact of AGNs on interacting systems, we present a spectral energy distribution (SED) analysis of a sample of 189 nearby galaxies. We gather and systematically re-reduce archival broad-band imaging mosaics from the ultraviolet to the far-infrared using data from GALEX, SDSS, 2MASS, IRAS, WISE, Spitzer, and Herschel. We use spectroscopy from Spitzer/IRS to obtain fluxes from fine-structure lines that trace star formation and AGN activity. Utilizing the SED modelling and fitting tool cigale, we derive the physical conditions of the interstellar medium, both in star-forming regions and in nuclear regions dominated by the AGN in these galaxies. We investigate how the star formation rates (SFRs) and the fractional AGN contributions (fAGN) depend on stellar mass, galaxy type, and merger stage. We find that luminous galaxies more massive than about $10^{10} \,\rm {M}_{*}$ are likely to deviate significantly from the conventional galaxy main-sequence relation. Interestingly, infrared AGN luminosity and stellar mass in this set of objects are much tighter than SFR and stellar mass. We find that buried AGNs may occupy a locus between bright starbursts and pure AGNs in the fAGN–[Ne v]/[Ne ii] plane. We identify a modest correlation between fAGN and mergers in their later stages.

scholarly journals High-resolution observations with ARTEMIS-JLS and the NRH

2019 ◽  
Vol 627 ◽  
pp. A133 ◽  
Author(s):  
C. E. Alissandrakis ◽  
C. Bouratzis ◽  
A. Hillaris
Keyword(s):  
Large Scale ◽  
Extreme Ultraviolet ◽  
Flux Rope ◽  
Low Noise ◽  
Continuum Emission ◽  
High Time Resolution ◽  
Flare Loop ◽  
Type Iv ◽  
Dynamic Spectra ◽  
The Continuum

Aims. We study the characteristics of intermediate drift bursts (fibers) embedded in a large type-IV event. Methods. We used high-sensitivity, low-noise dynamic spectra obtained with the acousto-optic analyzer (SAO) of the ARTEMIS-JLS solar radiospectrograph, in conjunction with high time-resolution images from the Nançay radioheliograph (NRH) and extreme ultraviolet (EUV) images from the Transition Region and Coronal Explorer (TRACE) to study fiber bursts during the large solar event of July 14, 2000. We computed both 2D and 1D images and applied high pass time filtering to the images and the dynamic spectrum in order to enhance the fiber-associated emission. For the study of the background continuum emission we used images averaged over several seconds. Results. Practically all fibers visible in the SAO dynamic spectra are identifiable in the NRH images. Fibers were first detected after the primary energy release in a moving type-IV event, probably associated with the rapid eastward expansion of the flare and the post-flare loop arcade. We found that fibers appeared as a modulation of the continuum intensity with a root mean square value of the order of 10%. Both the fibers and the continuum were strongly circularly polarized in the ordinary mode sense, indicating plasma emission at the fundamental. We detected a number of discrete fiber emission sources along two parallel stripes of ∼300 Mm in length, apparently segments of large-scale loops encompassing both the EUV loops and the CME-associated flux rope. We found cases of multiple fiber emissions appearing at slightly different positions and times; their consecutive appearance can give the impression of apparent motion with supra-luminal velocities. Images of individual fibers were very similar at 432.0 and 327.0 MHz. From the position shift of the sources and the time delays at low and high frequencies, we estimated the exciter speed and the frequency scale length along the loops for a well-observed group of fibers; we obtained consistent values from imaging and spectral data, supporting the whistler origin of the fiber emission. Finally we found that fibers in emission and fibers in absorption are very similar, confirming that they are manifestations of the same wave train.

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