| 1. |
- Bhagwat, Aniket, et al.
(författare)
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Cospatial 21 cm and metal-line absorbers in the epoch of reionization - I. Incidence and observability
- 2022
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 517:2, s. 2331-2342
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Tidskriftsartikel (refereegranskat)abstract
- Overdense, metal-rich regions, shielded from stellar radiation might remain neutral throughout reionization and produce metal as well as 21 cm absorption lines. Simultaneous absorption from metals and 21 cm can complement each other as probes of underlying gas properties. We use Aurora, a suite of high-resolution radiation-hydrodynamical simulations of galaxy formation, to investigate the occurrence of such 'aligned' absorbers. We calculate absorption spectra for 21 cm, O I , C II , SI II, and FE II. We find velocity windows with absorption from at least one metal and 21 cm, and classify the aligned absorbers into two categories: 'aligned and cospatial absorbers' and 'aligned but not cospatial absorbers'. While 'aligned and cospatial absorbers' originate from overdense structures and can be used to trace gas properties, 'aligned but not cospatial absorbers' are due to peculiar velocity effects. The incidence of absorbers is redshift dependent, as it is dictated by the interplay between reionization and metal enrichment, and shows a peak at z approximate to 8 for the aligned and cospatial absorbers. While aligned but not cospatial absorbers disappear towards the end of reionization because of the lack of an ambient 21 cm forest, aligned and cospatial absorbers are associated with overdense pockets of neutral gas that can be found at lower redshift. We produce mock observations for a set of sightlines for the next generation of telescopes like the ELT and SICA1-LOW, finding that given a sufficiently bright background quasar, these telescopes will be able to detect both types of absorbers throughout reionization.
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| 2. |
- Caruana, Joseph, et al.
(författare)
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The MUSE-Wide survey : a measurement of the Ly alpha emitting fraction among z > 3 galaxies
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 473:1, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the fraction of Lyman α (Ly α) emitters (XLy α) amongst HST continuum-selected galaxies at 3 < z < 6 with the Multi-Unit Spectroscopic Explorer (MUSE) on the VLT. Making use of the first 24 MUSE-Wide pointings in GOODS-South, each having an integration time of 1 h, we detect 100 Ly α emitters and find XLy α ≳ 0.5 for most of the redshift range covered, with 29 per cent of the Ly α sample exhibiting rest equivalent widths (rest-EWs) ≤ 15 Å. Adopting a range of rest-EW cuts (0–75 Å), we find no evidence of a dependence of XLy α on either redshift or ultraviolet luminosity.
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| 3. |
- Harker, Geraint J. A., et al.
(författare)
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Detection and extraction of signals from the epoch of reionization using higher-order one-point statistics
- 2009
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 393, s. 1449-1458
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Tidskriftsartikel (refereegranskat)abstract
- Detecting redshifted 21-cm emission from neutral hydrogen in the early Universe promises to give direct constraints on the epoch of reionization (EoR). It will, though, be very challenging to extract the cosmological signal (CS) from foregrounds and noise which are orders of magnitude larger. Fortunately, the signal has some characteristics which differentiate it from the foregrounds and noise, and we suggest that using the correct statistics may tease out signatures of reionization. We generate mock data cubes simulating the output of the Low Frequency Array (LOFAR) EoR experiment. These cubes combine realistic models for Galactic and extragalactic foregrounds and the noise with three different simulations of the CS. We fit out the foregrounds, which are smooth in the frequency direction, to produce residual images in each frequency band. We denoise these images and study the skewness of the one-point distribution in the images as a function of frequency. We find that, under sufficiently optimistic assumptions, we can recover the main features of the redshift evolution of the skewness in the 21-cm signal. We argue that some of these features - such as a dip at the onset of reionization, followed by a rise towards its later stages - may be generic, and give us a promising route to a statistical detection of reionization.
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| 4. |
- Harker, Geraint, et al.
(författare)
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Non-parametric foreground subtraction for 21-cm epoch of reionization experiments
- 2009
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 397, s. 1138-1152
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Tidskriftsartikel (refereegranskat)abstract
- One of the problems facing experiments designed to detect redshifted 21-cm emission from the epoch of reionization (EoR) is the presence of foregrounds which exceed the cosmological signal in intensity by orders of magnitude. While fitting them so that they can be removed, we must be careful to minimize `overfitting', in which we fit away some of the cosmological signal, and `underfitting', in which real features of the foregrounds cannot be captured by the fit, polluting the signal reconstruction. We argue that in principle it would be better to fit the foregrounds non-parametrically - allowing the data to determine their shape - rather than selecting some functional form in advance and then fitting its parameters. Non-parametric fits often suffer from other problems, however. We discuss these before suggesting a non-parametric method, Wp smoothing, which seems to avoid some of them. After outlining the principles of Wp smoothing, we describe an algorithm used to implement it. Some useful results for implementing an alternative algorithm are given in an appendix. We apply Wp smoothing to a synthetic data cube for the Low Frequency Array (LOFAR) EoR experiment. This cube includes realistic models for the signal, foregrounds, instrumental response and noise. The performance of Wp smoothing, measured by the extent to which it is able to recover the variance of the cosmological signal and to which it avoids the fitting residuals being polluted by leakage of power from the foregrounds, is compared to that of a parametric fit, and to another non-parametric method (smoothing splines). We find that Wp smoothing is superior to smoothing splines for our application, and is competitive with parametric methods even though in the latter case we may choose the functional form of the fit with advance knowledge of the simulated foregrounds. Finally, we discuss how the quality of the fit is affected by the frequency resolution and range, by the characteristics of the cosmological signal and by edge effects.
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| 5. |
- Harker, Geraint, et al.
(författare)
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Power spectrum extraction for redshifted 21-cm Epoch of Reionization experiments : the LOFAR case
- 2010
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 405:4, s. 2492-2504
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Tidskriftsartikel (refereegranskat)abstract
- One of the aims of the Low Frequency Array (LOFAR) Epoch of Reionization (EoR) project is to measure the power spectrum of variations in the intensity of redshifted 21-cm radiation from the EoR. The sensitivity with which this power spectrum can be estimated depends on the level of thermal noise and sample variance, and also on the systematic errors arising from the extraction process, in particular from the subtraction of foreground contamination. We model the extraction process using realistic simulations of the cosmological signal, the foregrounds and noise, and so estimate the sensitivity of the LOFAR EoR experiment to the redshifted 21-cm power spectrum. Detection of emission from the EoR should be possible within 360 h of observation with a single station beam. Integrating for longer, and synthesizing multiple station beams within the primary (tile) beam, then enables us to extract progressively more accurate estimates of the power at a greater range of scales and redshifts. We discuss different observational strategies which compromise between depth of observation, sky coverage and frequency coverage. A plan in which lower frequencies receive a larger fraction of the time appears to be promising. We also study the nature of the bias which foreground fitting errors induce on the inferred power spectrum and discuss how to reduce and correct for this bias. The angular and line-of-sight power spectra have different merits in this respect, and we suggest considering them separately in the analysis of LOFAR data.
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| 6. |
- Herenz, Edmund Christian, et al.
(författare)
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The MUSE-Wide survey : A first catalogue of 831 emission line galaxies
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 606
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Tidskriftsartikel (refereegranskat)abstract
- We present a first instalment of the MUSE-Wide survey, covering an area of 22.2 arcmin(2) (corresponding to similar to 20% of the final survey) in the CANDELS /Deep area of the Chandra Deep Field South. We use the MUSE integral field spectrograph at the ESO VLT to conduct a full-area spectroscopic mapping at a depth of 1 h exposure time per 1 arcmin(2) pointing. We searched for compact emission line objects using our newly developed LSDCat software based on a 3D matched filtering approach, followed by interactive classification and redshift measurement of the sources. Our catalogue contains 831 distinct emission line galaxies with redshifts ranging from 0.04 to 6. Roughly one third (237) of the emission line sources are Lyman alpha emitting galaxies with 3 < z < 6, only four of which had previously measured spectroscopic redshifts. At lower redshifts 351 galaxies are detected primarily by their [O i i] emission line (0.3 <= z <= 1.5), 189 by their [OIII] line (0.21 <= z <= 0.85), and 46 by their H alpha line (0.04 <= z <= 0.42). Comparing our spectroscopic redshifts to photometric redshift estimates from the literature, we find excellent agreement for z < 1.5 with a median Delta(z) of only similar to 4 x 10(-4) and an outlier rate of 6%, however a significant systematic offset of Delta(z) = 0.26 and an outlier rate of 23% for Ly alpha emitters at z > 3. Together with the catalogue we also release 1D PSF-weighted extracted spectra and small 3D datacubes centred on each of the 831 sources.
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| 7. |
- Herenz, Edmund Christian, et al.
(författare)
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The MUSE-Wide Survey : A determination of the Lyman alpha emitter luminosity function at 3 < z < 6
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 621
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the Lyman alpha emitter (LAE) luminosity function (LF) within the redshift range 2.9 <= z <= 6 from the first instalment of the blind integral field spectroscopic MUSE-Wide survey. This initial part of the survey probes a region of 22.2 arcmin(2) in the CANDELS/GOODS-S field (24 MUSE pointings with 1h integrations). The dataset provided us with 237 LAEs from which we construct the LAE LF in the luminosity range 42.2 <= log L-Ly alpha[erg s(-1)] <= 43.5 within a volume of 2.3 x 10(5) Mpc(3). For the LF construction we utilise three different non-parametric estimators: the classical 1/V-max method, the C- method, and an improved binned estimator for the differential LF. All three methods deliver consistent results, with the cumulative LAE LF being Phi(log L-Ly alpha[erg s(-1)] = 43.5) similar or equal to 3 x 10(-6) Mpc(-3) and Phi(log L-Ly alpha[erg s(-1)] = 42.2) similar or equal to 2 x 10(-3) Mpc(-3) towards the bright and faint end of our survey, respectively. By employing a non-parametric statistical test, and by comparing the full sample to subsamples in redshift bins, we find no supporting evidence for an evolving LAE LF over the probed redshift and luminosity range. Using a parametric maximum-likelihood technique we determine the best-fitting Schechter function parameters alpha = -1.84(-0.41)(+0.42) and log L*[erg s(-1)] = 42.2(-0.16)(+0.22) with the corresponding normalisation log phi*[Mpc(-3)] = -2.71. However, the dynamic range in Ly alpha luminosities probed by MUSE-Wide leads to a strong degeneracy between alpha and L*. Moreover, we find that a power-law parameterisation of the LF appears to be less consistent with the data compared to the Schechter function, even so when not excluding the X-Ray identified AGN from the sample. When correcting for completeness in the LAE LF determinations, we take into account that LAEs exhibit diffuse extended low surface brightness halos. We compare the resulting LF to one obtained by applying a correction assuming compact point-like emission. We find that the standard correction underestimates the LAE LF at the faint end of our survey by a factor of 2.5. Contrasting our results to the literature we find that at log L-Ly alpha[erg s(-1)] less than or similar to 42.5 previous LAE LF determinations from narrow-band surveys appear to be affected by a similar bias.
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| 8. |
- Johnson, Sean D., et al.
(författare)
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Galaxy and Quasar Fueling Caught in the Act from the Intragroup to the Interstellar Medium
- 2018
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 869:1
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of six spatially extended (10-100 kpc) line-emitting nebulae in the z approximate to 0.57 galaxy group hosting PKS 0405-123, one of the most luminous quasars at z < 1. The discovery is enabled by the Multi Unit Spectroscopic Explorer and provides tantalizing evidence connecting large-scale gas streams with nuclear activity on scales of <10 proper kpc (pkpc). One of the nebulae exhibits a narrow, filamentary morphology extending over 50 pkpc toward the quasar with narrow internal velocity dispersion (50 km s(-1)) and is not associated with any detected galaxies, consistent with a cool intragroup medium filament. Two of the nebulae are 10 pkpc north and south of the quasar with tidal-arm-like morphologies. These two nebulae, along with a continuum-emitting arm extending 60 pkpc from the quasar, are signatures of interactions that are expected to redistribute angular momentum in the host interstellar medium (ISM) to facilitate star formation and quasar fueling in the nucleus. The three remaining nebulae are among the largest and most luminous [O III] emitting blobs known (1400-2400 pkpc(2)) and correspond both kinematically and morphologically to interacting galaxy pairs in the quasar host group, consistent with arising from stripped ISM rather than large-scale quasar outflows. The presence of these large- and small-scale nebulae in the vicinity of a luminous quasar bears significantly on the effect of large-scale environment on galaxy and black hole fueling, providing a natural explanation for the previously known correlation between quasar luminosity and cool circumgalactic medium.
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| 9. |
- Leclercq, Floriane, et al.
(författare)
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The MUSE &ITHubble&IT Ultra Deep Field Survey VIII. Extended Lyman-alpha haloes around high-&ITz&IT star-forming galaxies
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- We report the detection of extended Ly alpha haloes around 145 individual star-forming galaxies at redshifts 3 <= z <= 6 in the Hubble Ultra Deep Field observed with the Multi-Unit Spectroscopic Explorer (MUSE) at ESO-VLT. Our sample consists of continuum-faint (-15 >= M-UV >= -22) Ly alpha emitters (LAEs). Using a 2D, two-component (continuum-like and halo) decomposition of Ly alpha emission assuming circular exponential distributions, we measure scale lengths and luminosities of Ly alpha haloes. We find that 80% of our objects having reliable Ly alpha halo measurements show Ly alpha emission that is significantly more extended than the UV continuum detected by HST (by a factor approximate to 4 to >20). The median exponential scale length of the Ly alpha haloes in our sample is approximate to 4.5 kpc with a few haloes exceeding 10 kpc. By comparing the maximal detected extent of the Ly alpha emission with the predicted dark matter halo virial radii of simulated galaxies, we show that the detected Ly alpha emission of our selected sample of Ly alpha emitters probes a significant portion of the cold circum-galactic medium of these galaxies (>50% in average). This result therefore shows that there must be significant HI reservoirs in the circum-galactic medium and reinforces the idea that Ly alpha haloes are ubiquitous around high-redshift Ly alpha emitting galaxies. Our characterization of the Ly alpha haloes indicates that the majority of the Ly alpha flux comes from the halo (approximate to 65%) and that their scale lengths seem to be linked to the UV properties of the galaxies (sizes and magnitudes). We do not observe a significant Ly alpha halo size evolution with redshift, although our sample for z > 5 is very small. We also explore the diversity of the Ly alpha line profiles in our sample and we find that the Ly alpha lines cover a large range of full width at half maximum (FWHM) from 118 to 512 km s(-1). While the FWHM does not seem to be correlated to the Ly alpha scale length, most compact Ly alpha haloes and those that are not detected with high significance tend to have narrower Ly alpha profiles (<350 km s(-1)). Finally, we investigate the origin of the extended Ly alpha emission but we conclude that our data do not allow us to disentangle the possible processes, i.e. scattering from star-forming regions, fluorescence, cooling radiation from cold gas accretion, and emission from satellite galaxies.
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| 10. |
- Patil, Ajinkya H., et al.
(författare)
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Constraining the epoch of reionization with the variance statistic : simulations of the LOFAR case
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 443:2, s. 1113-1124
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Tidskriftsartikel (refereegranskat)abstract
- Several experiments are underway to detect the cosmic-redshifted 21-cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signal-to-noise ratio, these observations aim for a statistical detection of the signal by measuring its power spectrum. We investigate the extraction of the variance of the signal as a first step towards detecting and constraining the global history of the EoR. Signal variance is the integral of the signal's power spectrum, and it is expected to be measured with a high significance. We demonstrate this through results from a simulation and parameter estimation pipeline developed for the Low-Frequency Array (LOFAR)-EoR experiment. We show that LOFAR should be able to detect the EoR in 600 h of integration using the variance statistic. Additionally, the redshift (z(r)) and duration (Delta z) of reionization can be constrained assuming a parametrization. We use an EoR simulation of z(r) = 7.68 and Delta(z) = 0.43 to test the pipeline. We are able to detect the simulated signal with a significance of four standard deviations and extract the EoR parameters as z(r) = 7.72(-0.18)(+0.37) and Delta z = 0.53(-0.23)(+0.12) in 600 h, assuming that systematic errors can be adequately controlled. We further show that the significance of detection and constraints on EoR parameters can be improved by measuring the cross-variance of the signal by cross-correlating consecutive redshift bins.
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