Theoretical and observational constraints on the H i intensity power spectrum

Mapping of the neutral hydrogen (H i) 21-cm intensity fluctuations across redshifts promises a novel and powerful probe of cosmology. The neutral hydrogen gas mass density $\Omega _{\rm H\,\small {i}}$ and bias parameter $b_{\rm H\,\small {i}}$ are key astrophysical inputs to the H i intensity fluctuation power spectrum. We compile the latest theoretical and observational constraints on $\Omega _{\rm H\,\small {i}}$ and $b_{\rm H\,\small {i}}$ at various redshifts in the post-reionization universe. Constraints are incorporated from galaxy surveys, H i intensity mapping experiments, damped Lyman α system observations, theoretical prescriptions for assigning H i to dark matter haloes and the results of numerical simulations. Using a minimum variance interpolation scheme, we obtain the predicted uncertainties on the H i intensity fluctuation power spectrum across redshifts 0-3.5 for three different confidence scenarios. We provide a convenient tabular form for the interpolated values of $\Omega _{\rm H\,\small {i}}$, $b_{\rm H\,\small {i}}$ and the H i power spectrum amplitude and their uncertainties. We discuss the consequences for the measurement of the power spectrum by current and future intensity mapping experiment

MIGHTEE-Hi: Evolution of Hi Scaling Relations of Star-forming Galaxies at z < 0.5*

We present the first measurements of H I galaxy scaling relations from a blind survey at z > 0.15. We perform spectral stacking of 9023 spectra of star-forming galaxies undetected in H I at 0.23 < z < 0.49, extracted from MIGHTEE-H I Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies in bins of galaxy properties (stellar mass M *, star formation rateSFR, and specific star formation rate sSFR, with sSFR ≡ M */SFR), obtaining ≳5σ detections in most cases, the strongest H I-stacking detections to date in this redshift range. With these detections, we are able to measure scaling relations in the probed redshift interval, finding evidence for a moderate evolution from the median redshift of our sample z med ~ 0.37 to z ~ 0. In particular, low-M * galaxies ( {\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 9 )experienceastrongHIdepletion( 0.5dexinlog10(MHI/M⊙) ), while massive galaxies ( {\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 11$ ) keep their H I mass nearly unchanged. When looking at the star formation activity, highly star-forming galaxies evolve significantly in M H I (f H I, where f H I ≡ M H I/M *) at fixed SFR (sSFR), while at the lowest probed SFR (sSFR) the scaling relations show no evolution. These findings suggest a scenario in which low-M * galaxies have experienced a strong H I depletion during the last ~5 Gyr, while massive galaxies have undergone a significant H I replenishment through some accretion mechanism, possibly minor mergers. Interestingly, our results are in good agreement with the predictions of the SIMBA simulation. We conclude that this work sets novel important observational constraints on galaxy scaling relations

Mightee-hi: Evolution of hi scaling relations of star-forming galaxies at z < 0.5*

We present the first measurements of H I galaxy scaling relations from a blind survey at z > 0.15. We perform spectral stacking of 9023 spectra of star-forming galaxies undetected in H I at 0.23 < z < 0.49, extracted from MIGHTEE-H I Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies in bins of galaxy properties (stellar mass M*, star formation rateSFR, and specific star formation rate sSFR, with sSFR ≡ M*/SFR), obtaining 5σ detections in most cases, the strongest H I-stacking detections to date in this redshift range. With these detections, we are able to measure scaling relations in the probed redshift interval, finding evidence for a moderate evolution from the median redshift of our sample zmed ∼ 0.37 to z ∼ 0. In particular, low-M* galaxies ( ~ * log 9 10( ) M M ) experience a strong H I depletion (∼0.5 dex in log10( ) M M H I ), while massive galaxies ( ~ * log 11 10( ) M M ) keep their H I mass nearly unchanged. When looking at the star formation activity, highly star-forming galaxies evolve significantly in MH I ( fH I, where fH I ≡ MH I/M*) at fixed SFR (sSFR), while at the lowest probed SFR (sSFR) the scaling relations show no evolution

Studies of neutral hydrogen gas in distant galaxies using the spectral stacking technique

Plin neutralnog vodika (HI) smatra se građevnom jedinicom galaksija jer služi kao primarno gorivo za stvaranje zvijezda. Izravna opažanja HI emisijske linije na 21 cm ograničena su granicama osjetljivosti radio teleskopa. Kako bi nadišli ovaj problem, koristimo relativno novu metodu slaganja spektara kako bi pomaknuli granice crvenih pomaka u radio opažanjima dalje nego li je moguće ostalim opažačkim metodama. U ovom radu predstavljena je statistička metoda slaganja HI spektara galaksija lociranih u tzv. G09 nebeskom polju, u rasponu crvenih pomaka 0.039<z<0.134. HI opažanja smiljena su Parkes radio teleskopom (New South Wales, Australija). Položaji galaksija i crveni pomaci nalaze se u katalogu dobavljenom iz baze podataka Galaxy and Mass Assembly (GAMA) istraživanja. Slažući spektre 7049 galaksija, ekstrahirane iz Parkes podatkovne kocke, postižemo dobar omjer signala i šuma, S/N=11.9. Šum pokazuje karakteristike Gaussiana, uz malo odstupanje zbog prisutnosti rezidualne radio-frekventne interferencije i emisije od snažnih izvora u podacima. Usrednjene veličine karakteristične HI dobivamo integrirajući složene spektre u granicama ±300 kms^−1 od sustava mirovanja. Taj raspon odgovara iznosu najveće očekivane širine HI profila. Srednja vrijednost gustoće toka, usrednjena masa HI i usrednjeni omjer mase i luminoziteta HI su (tim redoslijedom): (S)=(1.07±0.09)mJy, (M_HI)=(2.97±0.38)×10^9ℎ^−2M_⊙ i M_HI/L_r)=(1.58±0.39) M_⊙L_⊙^−1. Pri izračunu kozmičke gustoće mase HI (Ω_HI) testiramo dvije formule. Kako bi u izračun uključili i efekt konfuzije, koristimo faktor konfuzije.Neutral hydrogen gas (HI) is the building block of galaxies as it is a primary fuel for star formation. Direct observations of the HI 21 cm emission line are restricted by the limited sensitivities of radio telescopes. To overcome this issue, we employ the relatively new technique of spectral stacking to push the redshift limits of radio observations further than otherwise possible. This thesis presents an HI spectral stacking analysis of galaxies within the Galaxy and Mass Assembly (GAMA) 9^h field and over the redshift range 0.039< z <0.134. HI data was collected with the Parkes radio telescope in New South Wales, Australia. Galaxy positions and spectroscopic redshifts are provided by the GAMA survey. By co-adding the spectra of 7049 galaxies extracted from the Parkes data cube, we obtain a strong integrated signal-to-noise ratio of S/N=11.9. The rms noise behaves in a Gaussian manner, with slight deviation caused by the residual radio frequency interference and continuum source emission in the data. We measure average HI properties by integrating stacked spectra over ±300 kms^−1 from rest frame, the range equivalent to the maximum expected width of the HI profile. The resulting average flux density, average HI mass and average HI mass-to-light ratio are, respectively: (S)=(1.07±0.09)mJy, (M_HI)=(2.97±0.38)×10^9h^−2 M_⊙ and (M_HI/L_r)=(1.58±0.39)M_⊙L_⊙^1. We test two different strategies in calculating the cosmic HI mass density (ΩHI). To account for source confusion effect, we apply the confusion facto

Pathway to the Square Kilometre Array - The German White Paper -

The Square Kilometre Array (SKA) is the most ambitious radio telescope ever planned. With a collecting area of about a square kilometre, the SKA will be far superior in sensitivity and observing speed to all current radio facilities. The scientific capability promised by the SKA and its technological challenges provide an ideal base for interdisciplinary research, technology transfer, and collaboration between universities, research centres and industry. The SKA in the radio regime and the European Extreme Large Telescope (E-ELT) in the optical band are on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI) and have been recognised as the essential facilities for European research in astronomy. This "White Paper" outlines the German science and R&D interests in the SKA project and will provide the basis for future funding applications to secure German involvement in the Square Kilometre Array.Comment: Editors: H. R. Kl\"ockner, M. Kramer, H. Falcke, D.J. Schwarz, A. Eckart, G. Kauffmann, A. Zensus; 150 pages (low resolution- and colour-scale images), published in July 2012, language English (including a foreword and an executive summary in German), the original file is available via the MPIfR homepag

The BINGO project: I. Baryon acoustic oscillations from integrated neutral gas observations

Context. Observations of the redshifted 21-cm line of neutral hydrogen (HI) are a new and powerful window of observation that offers us the possibility to map the spatial distribution of cosmic HI and learn about cosmology. Baryon Acoustic Oscillations from Integrated Neutral Gas Observations (BINGO) is a new unique radio telescope designed to be one of the first to probe baryon acoustic oscillations (BAO) at radio frequencies. Aims. BINGO has two science goals: cosmology and astrophysics. Cosmology is the main science goal and the driver for BINGO's design and strategy. The key of BINGO is to detect the low redshift BAO to put strong constraints on the dark sector models and test the ICDM (cold dark matter) model. Given the versatility of the BINGO telescope, a secondary goal is astrophysics, where BINGO can help discover and study fast radio bursts (FRB) and other transients, as well as study Galactic and extragalactic science. In this paper, we introduce the latest progress of the BINGO project, its science goals, describing the scientific potential of the project for each goal and the new developments obtained by the collaboration. Methods. BINGO is a single dish transit telescope that will measure the BAO at low-z by making a 3D map of the HI distribution through the technique of intensity mapping over a large area of the sky. In order to achieve the project's goals, a science strategy and a specific pipeline for cleaning and analyzing the produced maps and mock maps was developed by the BINGO team, which we generally summarize here. Results. We introduce the BINGO project and its science goals and give a general summary of recent developments in construction, science potential, and pipeline development obtained by the BINGO Collaboration in the past few years. We show that BINGO will be able to obtain competitive constraints for the dark sector. It also has the potential to discover several FRBs in the southern hemisphere. The capacity of BINGO in obtaining information from 21-cm is also tested in the pipeline introduced here. Following these developments, the construction and observational strategies of BINGO have been defined. Conclusions. There is still no measurement of the BAO in radio, and studying cosmology in this new window of observations is one of the most promising advances in the field. The BINGO project is a radio telescope that has the goal to be one of the first to perform this measurement and it is currently being built in the northeast of Brazil. This paper is the first of a series of papers that describe in detail each part of the development of the BINGO project

NeutralUniverseMachine: An Empirical Model for the Evolution of HI and H2_2 Gas in the Universe

Accurately modeling the cold gas content in the universe is challenging for current theoretical models. We propose a new empirical model NeutralUniverseMachine for the evolution of HI and H$_2$ gas along with dark matter halos based on the UniverseMachine catalog. It is able to accurately describe the observed HI and H$_2$ mass functions, molecular-to-atomic ratio, HI-halo mass relation, HI/H$_2$-stellar mass relations at $z\sim0$, as well as the evolution of cosmic gas densities $\rho_{\rm HI}$ and $\rho_{\rm H_2}$ in $0<z<6$. The predictions from our model include: (i) There is weak evolution of HI mass function in $0<z<3$, but the evolution of H$_2$ mass function is much stronger at the massive end. (ii) The average HI and H$_2$ masses at a given stellar mass decrease by around 1 dex since $z=3$ for the star-forming galaxies, but the evolution for the quenched galaxies is much weaker. (iii) Star-forming galaxies have varying HI depletion time $\tau_{\rm HI}$ from 0.1 Gyr to 10 Gyr, and the dependence of $\tau_{\rm HI}$ on stellar mass and redshift is much stronger than those of H$_2$ depletion time. The quenched galaxies have much longer gas depletion time and weaker redshift evolution. (iv) The cosmic baryon density associated with galaxies is dominated by stars for $z<1.2$ and mainly contributed by HI gas at higher redshifts. (v) The HI bias gradually increases with the redshift from 0.69 to 2.33 in $0<z<3$ and is consistent with recent HI intensity mapping experiments.Comment: 27 pages, 21 figures. resubmitted to ApJ after the first report. Catalogs for gas masses available at https://halos.as.arizona.edu/UniverseMachine/DR1/Gas_Masses_NeutralUniverseMachine

Large-Scale Structure with 21cm Intensity Mapping

We are witnessing exciting times in the field of cosmology. Current and future experiments and surveys will provide us with tight constraints on the key cosmological parameters. A new and promising technique of mapping the Large-Scale Structure (LSS) in our Universe is the 21cm Intensity Mapping (IM) in which one uses the emission of the neutral hydrogen as a tracer of the underlying matter field. In principle this technique can be used to map huge portions of our Universe and deliver 3D structure measurements providing us with the information that is complementary to the information extracted from the Cosmic Microwave Background (CMB) experiments. However, the field of 21cm IM cosmology is still in its raising and is severely limited by the foreground issues and problems. In this thesis we will consider several aspects of using the 21cm IM as an LSS probe in order to better constrain the cosmological parameters. First, we present and analyse a Baryon Acoustic Oscillation (BAO) reconstruction method that consists of displacing pixels instead of galaxies and whose implementation is easier than the standard reconstruction method. We show that this method is equivalent to the standard reconstruction technique in the limit where the number of pixels becomes very large. This method is particularly useful in surveys where individual galaxies are not resolved, as in 21cm IM observations. We validate this method by reconstructing mock pixelated maps, that we build from the distribution of matter and halos in real- and redshift-space, from a large set of numerical simulations. We find that this method is able to decrease the uncertainty in the BAO peak position by 30-50% over the typical angular resolution scales of 21cm IM experiments. Second, we investigate the possibility of performing cosmological studies in the redshift range 2.5 < z < 5 through suitable extensions of existing and upcoming radio-telescopes like CHIME, HIRAX and FAST. We use the Fisher matrix technique to forecast the bounds that those instruments can place on the growth rate, the BAO distance scale parameters, the sum of the neutrino masses and the number of relativistic degrees of freedom at decoupling, Neff. We point out that quantities that depend on the amplitude of the 21cm power spectrum, like f\u3c38, are completely degenerate with \u3a9HI and bHI. Then, we propose several strategies to independently constrain them through cross-correlations with other probes. We study in detail the dependence of our results on the instrument, amplitude of the HI bias, the foreground wedge coverage, the nonlinear scale used in the analysis, uncertainties in the theoretical modeling and the priors on bHI and \u3a9HI. We conclude that 21cm IM surveys operating in this redshift range can provide extremely competitive constraints on key cosmological parameters. Thridly, we have used TNG100, a large state-of-the-art magneto-hydrodynamic simulation of a 75 h 121 Mpc box size, which is part of the IllustrisTNG Project, to study the neutral hydrogen density profiles in dark matter halos. We find that while the density profiles of HI exhibit a large halo-to-halo scatter, the mean profiles are universal across mass and redshift. Finally, we combine information from the clustering of HI galaxies in the 100% data release of the Arecibo Legacy Fast ALFA survey (ALFALFA), and from the HI content of optically-selected galaxy groups found in the Sloan Digital Sky Survey (SDSS) to constrain the relation between halo mass Mh and its average total HI mass content MHI. We model the abundance and clustering of neutral hydrogen through a halo-model-based approach, parametrizing the MHI(Mh) relation as a power law with an exponential mass cutoff. To break the degeneracy between the amplitude and low-mass cutoff of the MHI(Mh) relation, we also include a recent measurement of the cosmic HI abundance from the 100% ALFALFA sample. We find that all datasets are consistent with a power-law index \u3b1 = 0.44\ub10.08 and a cutoff halo mass log10 Mmin /(h^ 121M 99) = 11.27+0.24 120.30. We compare these results with predictions from state-of-the-art magneto-hydrodynamical simulations, and find both to be in good qualitative agreement, although the data favours a significantly larger cutoff mass that is consistent with the higher cosmic HI abundance found in simulations. Both data and simulations seem to predict a similar value for the HI bias (bHI = 0.875 \ub1 0.022) and shot-noise power (PSN = 92+20-18 [h^ 121Mpc]^3) at redshift z = 0

Pathway to the Square Kilometre Array - The German White Paper -

The Square Kilometre Array (SKA) is the most ambitious radio telescope ever planned. With a collecting area of about a square kilometre, the SKA will be far superior in sensitivity and observing speed to all current radio facilities. The scientific capability promised by the SKA and its technological challenges provide an ideal base for interdisciplinary research, technology transfer, and collaboration between universities, research centres and industry. The SKA in the radio regime and the European Extreme Large Telescope (E-ELT) in the optical band are on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI) and have been recognised as the essential facilities for European research in astronomy. This "White Paper" outlines the German science and R&D interests in the SKA project and will provide the basis for future funding applications to secure German involvement in the Square Kilometre Array