arXiv subjects

Yin-Zhe Ma

Publications and source records attributed to Yin-Zhe Ma.

At least 91 records · Page 5Linked to original sources

arXiv2019

A Search for Warm/Hot Gas Filaments Between Pairs of SDSS Luminous Red Galaxies

We search the Planck data for a thermal Sunyaev-Zel'dovich (tSZ) signal due to gas filaments between pairs of Luminous Red Galaxies (LRG's) taken from the Sloan Digital Sky Survey Data Release 12 (SDSS/DR12). We identify $\sim$260,000 LRG pairs in the DR12 catalog that lie within 6-10 $h^{-1} \mathrm{Mpc}$ of each other in tangential direction and within 6 $h^{-1} \mathrm{Mpc}$ in radial direction. We stack pairs by rotating and scaling the angular positions of each LRG so they lie on a common reference frame, then we subtract a circularly symmetric halo from each member of the pair to search for a residual signal between the pair members. We find a statistically significant (5.3$σ$) signal between LRG pairs in the stacked data with a magnitude $Δy = (1.31 \pm 0.25) \times 10^{-8}$. The uncertainty is estimated from two Monte Carlo null tests which also establish the reliability of our analysis. Assuming a simple, isothermal, cylindrical filament model of electron over-density with a radial density profile proportional to $r_c/r$ (as determined from simulations), where $r$ is the perpendicular distance from the cylinder axis and $r_c$ is the core radius of the density profile, we constrain the product of over-density and filament temperature to be $δ_c \times (T_{\rm e}/10^7 \, {\rm K}) \times (r_c/0.5h^{-1} \, {\rm Mpc}) = 2.7 \pm 0.5$. To our knowledge, this is the first detection of filamentary gas at over-densities typical of cosmological large-scale structure. We compare our result to the BAHAMAS suite of cosmological hydrodynamic simulations (McCarthy et al. 2017) and find a slightly lower, but marginally consistent Comptonization excess, $Δy = (0.84 \pm 0.24) \times 10^{-8}$.

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arXiv2019

Probing Diffuse Gas with Fast Radio Bursts

The dispersion measure -- redshift relation of Fast Radio Bursts, $\mathrm{DM}(z)$, has been proposed as a potential new probe of the cosmos, complementary to existing techniques. In practice, however, the effectiveness of this approach depends on a number of factors, including (but not limited to) the intrinsic scatter in the data caused by intervening matter inhomogeneities. Here, we simulate a number of catalogues of mock FRB observations, and use MCMC techniques to forecast constraints, and assess which parameters will likely be best constrained. In all cases we find that any potential improvement in cosmological constraints are limited by the current uncertainty on the the diffuse gas fraction, $f_{\rm d}(z)$. Instead, we find that the precision of current cosmological constraints allows one to constrain $f_{\rm d}(z)$, and possibly its redshift evolution. Combining CMB + BAO + SNe + $H_0$ constraints with just 100 FRBs (with redshifts), we find a typical constraint on the mean diffuse gas fraction of a few percent. A detection of this nature would alleviate the "missing baryon problem", and therefore highlights the value of localisation and spectroscopic followup of future FRB detections.

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arXiv2019

Forecasts of cosmological constraints from HI intensity mapping with FAST, BINGO & SKA-I

We forecast the cosmological constraints of the neutral hydrogen (HI) intensity mapping (IM) technique with radio telescopes by assuming 1-year of observational time. The current and future radio telescopes we consider here are FAST (Five hundred meter Aperture Spherical Telescope), BINGO (Baryon acoustic oscillations In Neutral Gas Observations), and SKA-I (Square Kilometre Array phase I) single-dish experiment. We also forecast the combined constraints of the three radio telescopes with Planck. We find that, the $1 σ$ errors of $(w_{0}, w_{a})$ for BINGO, FAST and SKA-I with respect to the fiducial values are respectively, $(0.9293, 3.5792), (0.4083, 1.5878), (0.3158, 0.4622)$. This is equivalent to $(56.04\%, 55.64\%)$ and $(66.02\%, 87.09\%)$ improvements in constraining $(w_{0}, w_{a})$ for FAST and SKA-I relative to BINGO. Simulations further show that SKA-I will put more stringent constraints than both FAST and BINGO when each of the experiment is combined with Planck measurement. For the $9$ cosmological parameters in consideration, we find that, there is a trade-off between SKA-I and FAST in constraining cosmological parameters, with each experiment being more superior in constraining a particular set of parameters.

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arXiv2019

Searching for HI imprints in cosmic web filaments with 21-cm intensity mapping

We investigate the possible presence of neutral hydrogen (HI) in intergalactic filaments at very low redshift ($z\sim 0.08$), by stacking a set of 274,712 2dFGRS galaxy pairs over 21-cm maps obtained with dedicated observations conducted with the Parkes radio telescope, over a total sky area of approximately 1,300 square degrees covering two patches in the northern and in the southern Galactic hemispheres. The stacking is performed by combining local maps in which each pair is brought to a common reference frame; the resulting signal from the edge galaxies is then removed to extract the filament residual emission. We repeat the analysis on maps cleaned removing either 10 or 20 foreground modes in a principal component analysis. Our study does not reveal any clear HI excess in the considered filaments in either case; we determine upper limits on the total filament HI brightness temperature at $T_{\rm b} \lesssim 10.3 \,μ\text{K}$ for the 10-mode and at $T_{\rm b} \lesssim 4.8 \,μ\text{K}$ for the 20-mode removed maps at the 95% confidence level. These estimates translate into upper limits for the local filament HI density parameter, $Ω_{\rm HI}^{\rm (f)} \lesssim 7.0\times10^{-5}$ and $Ω_{\rm HI}^{\rm (f)} \lesssim 3.2\times10^{-5}$ respectively, and for the HI column density, $N_{\rm HI} \lesssim 4.6\times10^{15}\,\text{cm}^{-2}$ and $N_{\rm HI} \lesssim 2.1\times10^{15}\,\text{cm}^{-2}$ respectively. These column density constraints are consistent with previous detections of HI in the warm-hot intergalactic medium obtained observing broad Ly $α$ absorption systems. The present work shows for the first time how such constraints can be achieved using the stacking of galaxy pairs on 21-cm maps.

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arXiv2019

Research and Development for HI Intensity Mapping

Development of the hardware, data analysis, and simulation techniques for large compact radio arrays dedicated to mapping the 21 cm line of neutral hydrogen gas has proven to be more difficult than imagined twenty years ago when such telescopes were first proposed. Despite tremendous technical and methodological advances, there are several outstanding questions on how to optimally calibrate and analyze such data. On the positive side, it has become clear that the outstanding issues are purely technical in nature and can be solved with sufficient development activity. Such activity will enable science across redshifts, from early galaxy evolution in the pre-reionization era to dark energy evolution at low redshift.

astro-ph.IM↗

arXiv2019

A Roadmap for Astrophysics and Cosmology with High-Redshift 21 cm Intensity Mapping

In this white paper, we lay out a US roadmap for high-redshift 21 cm cosmology (30 < z < 6) in the 2020s. Beginning with the currently-funded HERA and MWA Phase II projects and advancing through the decade with a coordinated program of small-scale instrumentation, software, and analysis projects targeting technology development, this roadmap incorporates our current best understanding of the systematics confronting 21 cm cosmology into a plan for overcoming them, enabling next-generation, mid-scale 21 cm arrays to be proposed late in the decade. Submitted for consideration by the Astro2020 Decadal Survey Program Panel for Radio, Millimeter, and Submillimeter Observations from the Ground as a Medium-Sized Project.

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arXiv2019

Probing galaxy cluster and intra-cluster gas with luminous red galaxies

We use the cross-correlation between the thermal Sunyaev-Zeldovich (tSZ) signal measured by the Planck satellite and the luminous red galaxy (LRG) samples provided by the SDSS DR7 to study the properties of galaxy cluster and intra-cluster gas. We separate the samples into three redshift bins z_1=(0.16, 0.26), z_2=(0.26, 0.36), z_3=(0.36, 0.47), and stack the Planck y-map against LRGs to derive the averaged y-profile for each redshift bin. We then fit the stacked profile with the theoretical prediction from the universal pressure profile (UPP) by using the Markov-Chain Monte-Carlo method. We find that the best-fit values of the UPP parameters for the three bins are generally consistent with the previous studies, except for the noticeable evolution of the parameters in the three redshift bins. We simultaneously fit the data in the three redshift bins together, and find that the original UPP model cannot fit the data at small angular scales very well in the first and third redshift bins. The joint fits can be improved by including an additional parameter eta to change the redshift-dependence of the model (i.e. E(z)^{8/3} -> E(z)^{8/3+eta}) with best-fit value as eta=-3.11^{+1.09}_{-1.13}. This suggests that the original UPP model with less redshift-dependence may provide a better fit to the stacked thermal Sunyaev-Zeldovich profile.

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arXiv2019

Astro2020 Science White Paper: Synergies Between Galaxy Surveys and Reionization Measurements

The early phases of galaxy formation constitute one of the most exciting frontiers in astrophysics. It is during this era that the first luminous sources reionize the intergalactic medium - the moment when structure formation affects every baryon in the Universe. Here we argue that we will obtain a complete picture of this era by combining observations of galaxies with direct measurements of the reionization process: the former will provide a detailed understanding of bright sources, while the latter will constrain the (substantial) faint source population. We further describe how optimizing the comparison of these two measurements requires near-infrared galaxy surveys covering large volumes and retaining redshift information and also improvements in 21-cm analysis, moving those experiments into the imaging regime.

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arXiv2019

Astro2020 Science White Paper: Insights Into the Epoch of Reionization with the Highly-Redshifted 21-cm Line

The epoch of reionization, when photons from early galaxies ionized the intergalactic medium about a billion years after the Big Bang, is the last major phase transition in the Universe's history. Measuring the characteristics of the transition is important for understanding early galaxies and the cosmic web and for modeling dwarf galaxies in the later Universe. But such measurements require probes of the intergalactic medium itself. Here we describe how the 21-cm line of neutral hydrogen provides a powerful probe of the reionization process and therefore important constraints on both the galaxies and intergalactic absorbers at that time. While existing experiments will make precise statistical measurements over the next decade, we argue that improved 21-cm analysis techniques - allowing imaging of the neutral gas itself - as well as improved theoretical models, are crucial for testing our understanding of this important era.

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arXiv2019

Astro 2020 Science White Paper: Fundamental Cosmology in the Dark Ages with 21-cm Line Fluctuations

The Dark Ages are the period between the last scattering of the cosmic microwave background and the appearance of the first luminous sources, spanning approximately 1100 < z < 30. The only known way to measure fluctuations in this era is through the 21-cm line of neutral hydrogen. Such observations have enormous potential for cosmology, because they span a large volume while the fluctuations remain linear even on small scales. Observations of 21-cm fluctuations during this era can therefore constrain fundamental aspects of our Universe, including inflation and any exotic physics of dark matter. While the observational challenges to these low-frequency 21-cm observations are enormous, especially from the terrestrial environment, they represent an important goal for cosmology.

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arXiv2019

Astro2020 Science White Paper: First Stars and Black Holes at Cosmic Dawn with Redshifted 21-cm Observations

The "cosmic dawn" refers to the period of the Universe's history when stars and black holes first formed and began heating and ionizing hydrogen in the intergalactic medium (IGM). Though exceedingly difficult to detect directly, the first stars and black holes can be constrained indirectly through measurements of the cosmic 21-cm background, which traces the ionization state and temperature of intergalactic hydrogen gas. In this white paper, we focus on the science case for such observations, in particular those targeting redshifts z $\gtrsim$ 10 when the IGM is expected to be mostly neutral. 21-cm observations provide a unique window into this epoch and are thus critical to advancing first star and black hole science in the next decade.

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arXiv2019

Cosmology with the Highly Redshifted 21cm Line

In addition to being a probe of Cosmic Dawn and Epoch of Reionization astrophysics, the 21cm line at $z>6$ is also a powerful way to constrain cosmology. Its power derives from several unique capabilities. First, the 21cm line is sensitive to energy injections into the intergalactic medium at high redshifts. It also increases the number of measurable modes compared to existing cosmological probes by orders of magnitude. Many of these modes are on smaller scales than are accessible via the CMB, and moreover have the advantage of being firmly in the linear regime (making them easy to model theoretically). Finally, the 21cm line provides access to redshifts prior to the formation of luminous objects. Together, these features of 21cm cosmology at $z>6$ provide multiple pathways toward precise cosmological constraints. These include the "marginalizing out" of astrophysical effects, the utilization of redshift space distortions, the breaking of CMB degeneracies, the identification of signatures of relative velocities between baryons and dark matter, and the discovery of unexpected signs of physics beyond the $Λ$CDM paradigm at high redshifts.

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arXiv2019

Mapping Cosmic Dawn and Reionization: Challenges and Synergies

Cosmic dawn and the Epoch of Reionization (EoR) are among the least explored observational eras in cosmology: a time at which the first galaxies and supermassive black holes formed and reionized the cold, neutral Universe of the post-recombination era. With current instruments, only a handful of the brightest galaxies and quasars from that time are detectable as individual objects, due to their extreme distances. Fortunately, a multitude of multi-wavelength intensity mapping measurements, ranging from the redshifted 21 cm background in the radio to the unresolved X-ray background, contain a plethora of synergistic information about this elusive era. The coming decade will likely see direct detections of inhomogenous reionization with CMB and 21 cm observations, and a slew of other probes covering overlapping areas and complementary physical processes will provide crucial additional information and cross-validation. To maximize scientific discovery and return on investment, coordinated survey planning and joint data analysis should be a high priority, closely coupled to computational models and theoretical predictions.

astro-ph.CO↗

arXiv2019

Cosmic Dawn and Reionization: Astrophysics in the Final Frontier

The cosmic dawn and epoch of reionization mark the time period in the universe when stars, galaxies, and blackhole seeds first formed and the intergalactic medium changed from neutral to an ionized one. Despite substantial progress with multi-wavelength observations, astrophysical process during this time period remain some of the least understood with large uncertainties on our existing models of galaxy, blackhole, and structure formation. This white paper outlines the current state of knowledge and anticipated scientific outcomes with ground and space-based astronomical facilities in the 2020s. We then propose a number of scientific goals and objectives for new facilities in late 2020s to mid 2030s that will lead to definitive measurements of key astrophysical processes in the epoch of reionization and cosmic dawn.

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arXiv2019

Constraining the reionization history with CMB and spectroscopic observations

We investigate the constraints on the reionization history of the Universe from a joint analysis of the cosmic microwave background and neutral hydrogen fraction data. The $\tanh$ parametrization and principal component analysis methods are applied to the reionization history respectively. The commonly used $\tanh$ parametrization is oversimplistic when the neutral hydrogen fraction data are taken into account. Using the principal component analysis method, the reconstructed reionization history is consistent with the neutral hydrogen fraction data. With the principal component analysis method, we reconstruct the neutral hydrogen fraction at $z=9.75$ as $x_{\text{HI}}=0.69^{+0.30}_{-0.32}$ for $6<z<20$ range reconstruction, and $x_{\text{HI}}=0.76^{+0.22}_{-0.27}$ for $6<z<30$ range reconstruction. These results suggest that the Universe began to reionize at redshift no later than $z=10$ at a $95\%$ confidence level.

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arXiv2018

Constraining the interaction between dark sectors with future HI intensity mapping observations

We study a model of interacting dark matter and dark energy, in which the two components are coupled. We calculate the predictions for the 21-cm intensity mapping power spectra, and forecast the detectability with future single-dish intensity mapping surveys (BINGO, FAST and SKA-I). Since dark energy is turned on at $z\sim 1$, which falls into the sensitivity range of these radio surveys, the HI intensity mapping technique is an efficient tool to constrain the interaction. By comparing with current constraints on dark sector interactions, we find that future radio surveys will produce tight and reliable constraints on the coupling parameters.

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arXiv2018

21cm Limits on Decaying Dark Matter and Primordial Black Holes

Recently the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) reported the detection of a 21cm absorption signal stronger than astrophysical expectations. In this paper we study the impact of radiation from dark matter (DM) decay and primordial black holes (PBH) on the 21cm radiation temperature in the reionization epoch, and impose a constraint on the decaying dark matter and PBH energy injection in the intergalactic medium, which can heat up neutral hydrogen gas and weaken the 21cm absorption signal. We consider decay channels DM$\rightarrow e^+e^-, γγ$, $μ^+μ^-$, $b\bar{b}$ and the $10^{15-17}$g mass range for primordial black holes, and require the heating of the neutral hydrogen does not negate the 21cm absorption signal. For $e^+e^-$, $γγ$ final states and PBH cases we find strong 21cm bounds that can be more stringent than the current extragalactic diffuse photon bounds. For the DM$\rightarrow e^+e^-$ channel, the lifetime bound is $τ_{\rm DM}> 10^{27}$s for sub-GeV dark matter. The bound is $τ_{\rm DM}\ge 10^{26}$s for sub-GeV DM$\rightarrow γγ$ channel and reaches $10^{27}$s at MeV DM mass. For $b\bar{b}$ and $μ^+μ^-$ cases, the 21 cm constraint is better than all the existing constraints for $m_{\rm DM}<20$ GeV where the bound on $τ_{\rm DM}\ge10^{26}$s. For both DM decay and primordial black hole cases, the 21cm bounds significantly improve over the CMB damping limits from Planck data.

astro-ph.HE↗

arXiv2018

Future Cosmological Constraints from Fast Radio Bursts

We consider the possible observation of Fast Radio Bursts (FRBs) with planned future radio telescopes, and investigate how well the dispersions and redshifts of these signals might constrain cosmological parameters. We construct mock catalogues of FRB dispersion measure (DM) data and employ Markov Chain Monte Carlo (MCMC) analysis, with which we forecast and compare with existing constraints in the flat $Λ$CDM model, as well as some popular extensions that include dark energy equation of state and curvature parameters. We find that the scatter in DM observations caused by inhomogeneities in the intergalactic medium (IGM) poses a big challenge to the utility of FRBs as a cosmic probe. Only in the most optimistic case, with a high number of events and low IGM variance, do FRBs aid in improving current constraints. In particular, when FRBs are combined with CMB+BAO+SNe+$H_0$ data, we find the biggest improvement comes in the $Ω_{\mathrm b}h^2$ constraint. Also, we find that the dark energy equation of state is poorly constrained, while the constraint on the curvature parameter $Ω_k$, shows some improvement when combined with current constraints. When FRBs are combined with future BAO data from 21cm Intensity Mapping (IM), we find little improvement over the constraints from BAOs alone. However, the inclusion of FRBs introduces an additional parameter constraint, $Ω_{\mathrm b}h^2$, which turns out to be comparable to existing constraints. This suggest that FRBs provide valuable information about the cosmological baryon density in the intermediate redshift Universe, independent of high redshift CMB data.

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