ABSTRACT We report a Giant Metrewave Radio Telescope search for H i 21 cm emission from a large sample of massive star-forming galaxies at z 1.18-1.34, lying in sub-fields of the DEEP2 Redshift ...Survey. The search was carried out by co-adding ("stacking") the H i 21 cm emission spectra of 857 galaxies, after shifting each galaxy's H i 21 cm spectrum to its rest frame. We obtain the 3 upper limit SH i < 2.5 Jy on the average H i 21 cm flux density of the 857 galaxies, at a velocity resolution of 315 km s−1. This yields the 3 constraint on the average H i mass of the 857 stacked galaxies, the first direct constraint on the atomic gas mass of galaxies at z > 1. The implied limit on the average atomic gas mass fraction (relative to stars) is MGAS/M* < 0.5, comparable to the cold molecular gas mass fraction in similar star-forming galaxies at these redshifts. We find that the cosmological mass density of neutral atomic gas in massive star-forming galaxies at z 1.3 is GAS < 3.7 × 10−4, significantly lower than GAS estimates in both galaxies in the local universe and damped Ly absorbers at z ≥ 2.2. Massive blue star-forming galaxies thus do not appear to dominate the neutral atomic gas content of the universe at z 1.3.
Abstract
The origin of spectral curvature at energies
E
≃ 10 keV in ultraluminous X-ray sources (ULXs) is not well understood. In this paper, we propose a novel mechanism based on synchrotron ...radiation to explain this cutoff. We show that relativistic plasma can give rise to the observed spectral curvature for neutron star magnetic fields due to the variation in the latitude of synchrotron radiation. We analyze the NuSTAR data of two bright pulsar ULXs, NGC 5907 ULX1 and NGC 7793 P13, and provide estimates of the physical parameters of these sources. We fit the data for synchrotron emission at various latitudes and show that the spectral cutoff in these cases can be explained for a large range of acceptable physical parameters, e.g., a semirelativistic plasma with
γ
≃ 20 for high latitudes or a highly relativistic plasma (
γ
≃ 10
5
) for emission close to the electron’s orbital plane in a typical magnetic field of
B
≃ 10
12
G. We also discuss how such an emission mechanism can be distinguished from other proposed models. A corollary to our study is that most ULXs might be neutron stars as they display such a spectral cutoff.
The skin is an attractive tissue target for vaccination, as it is readily accessible and contains a dense population of antigen-presenting and immune-accessory cells. Microneedle arrays (MNAs) are ...emerging as an effective tool for in situ engineering of the cutaneous microenvironment to enable diverse immunization strategies. Here, we present novel dissolving undercut MNAs and demonstrate their application for effective multicomponent cutaneous vaccination. The MNAs are composed of micron-scale needles featuring pyramidal heads supported by undercut stem regions with filleted bases to ensure successful skin penetration and retention during application. Prior efforts to fabricate dissolving undercut microstructures were limited and required complex and lengthy processing and assembly steps. In the current study, we strategically combine three-dimensional (3D) laser lithography, an emerging micro-additive manufacturing method with unique geometric capabilities and nanoscale resolution, and micromolding with favorable materials. This approach enables reproducible production of dissolving MNAs with undercut microneedles that can be tip-loaded with multiple biocargos, such as antigen (ovalbumin) and adjuvant (Poly(I:C)). The resulting MNAs fulfill the geometric (sharp tips and smooth edges) and mechanical-strength requirements for failure-free penetration of human and murine skin to simultaneously deliver multicomponent (antigen plus adjuvant) vaccines to the same cutaneous microenvironment. Cutaneous vaccination of mice using these MNAs induces more potent antigen-specific cellular and humoral immune responses than those elicited by traditional intramuscular injection. Together, the unique geometric features of these undercut MNAs and the associated manufacturing strategy, which is compatible with diverse drugs and biologics, could enable a broad range of non-cutaneous and cutaneous drug delivery applications, including multicomponent vaccination.
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•Combines 3D laser lithography with nanoscale resolution and micromolding to manufacture dissolving microneedle arrays (MNAs)•Microneedles with undercut geometries can be directly removed from flexible molds, simplifying their fabrication•First demonstration of dissolving undercut MNAs incorporating antigen plus adjuvant vaccine components•MNAs simultaneously deliver antigen and adjuvant to the same cutaneous microenvironment in both human and murine skin•OVA ± Poly(I:C) MNAs elicit more potent cellular and humoral immunity than traditional intramuscular vaccination
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
ABSTRACT
The detection of redshifted hyperfine line of neutral hydrogen (H i) is the most promising probe of the epoch of reionization (EoR). We report an analysis of 55 h of Murchison Widefield ...Array (MWA) phase II drift scan EoR data. The data correspond to a central frequency $\nu _0 = 154.24 \, \rm MHz$ (z ≃ 8.2 for the redshifted H i hyperfine line) and bandwidth $B = 10.24 \, \rm MHz$. As one expects greater system stability in a drift scan, we test the system stability by comparing the extracted power spectra from data with noise simulations and show that the power spectra for the cleanest data behave as thermal noise. We compute the H i power spectrum as a function of time in one and two dimensions. The best upper limit on the 1D power spectrum are: $\Delta ^2(k) \simeq (1000~\rm mK)^2$ at k ≃ 0.2h Mpc−1 and at k ≃ 1h Mpc−1. The cleanest modes, which might be the most suited for obtaining the optimal signal to noise, correspond to k ≳ 1h Mpc−1. We also study the time-dependence of the foreground-dominated modes in a drift scan and compare with the expected behaviour.
Abstract
We report a ≈400 hr Giant Metrewave Radio Telescope (GMRT) search for H
i
21 cm emission from star-forming galaxies at
z
= 1.18–1.39 in seven fields of the DEEP2 Galaxy Survey. Including ...data from an earlier 60 hr GMRT observing run, we co-added the H
i
21 cm emission signals from 2841 blue star-forming galaxies that lie within the FWHM of the GMRT primary beam. This yielded a 5.0
σ
detection of the average H
i
21 cm signal from the 2841 galaxies at an average redshift 〈
z
〉 ≈ 1.3, only the second detection of H
i
21 cm emission at
z
≥ 1. We obtain an average H
i
mass of 〈M
HI
〉 = (3.09 ± 0.61) × 10
10
M
⊙
and an H
i
-to-stellar mass ratio of 2.6 ± 0.5, both significantly higher than values in galaxies with similar stellar masses in the local universe. We also stacked the 1.4 GHz continuum emission of the galaxies to obtain a median star formation rate (SFR) of 14.5 ± 1.1 M
⊙
yr
−1
. This implies an average H
i
depletion timescale of ≈2 Gyr for blue star-forming galaxies at
z
≈ 1.3, a factor of ≈3.5 lower than that of similar local galaxies. Our results suggest that the H
i
content of galaxies toward the end of the epoch of peak cosmic SFR density is insufficient to sustain their high SFR for more than ≈2 Gyr. Insufficient gas accretion to replenish the H
i
could then explain the observed decline in the cosmic SFR density at
z
< 1.
The 21-cm line emitted by neutral hydrogen (HI) during the Dark Ages carries imprints of pristine primordial correlations. In models of inflation driven by a single, canonical scalar field, we show ...that a phase of ultra-slow-roll can lead to a null in all the primordial correlations at a specific wave number k_{dip}. We consider scenarios wherein the null in the correlations occurs over wave numbers 1≲k_{dip}≲10 Mpc^{-1}, and examine the prospects of detecting such a damping in the HI signal due to the nulls at the level of power and bispectra in future observational missions.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Abstract In recent years, the detection of gravitational waves by LIGO and PTA collaborations have raised the intriguing possibility of excess matter power at small scales. Such an increase can be ...achieved by ultra slow roll (USR) phase during inflationary epoch. We constrain excess power over small scales within the framework of such models using cosmological datasets, particularly of CMB anisotropies and Lyman- α . We parameterize the USR phase in terms of the e-fold at the onset of USR (counted from the end of inflation) N̅ 1 and the duration of USR phase Δ N. The former dictates the scale of enhancement in the primordial power spectrum, while the latter determines the amplitude of such an enhancement. From a joint dataset of CMB and galaxy surveys, we obtain N̅ 1 ≲ 45 with no bound on Δ N. This in turn implies that the scales over which the power spectrum can deviate significantly from the nearly scale invariant behavior of a typical slow-roll model is k ≳1 Mpc -1 . On the other hand, the Lyman- α data is sensitive to baryonic power spectrum along the line of sight. We consider a semi-analytic theoretical method and high spectral-resolution Lyman- α data to constrain the model. The Lyman-α data limits both the USR parameters: N̅ 1 ≲ 41 and Δ N ≲ 0.4. This constrains the amplitude of the power spectrum enhancement to be less than a factor of hundred over scales 1 ≲ k/ Mpc -1 ≲ 100, thereby considerably improving the constraint on power over these scales as compared to the bounds arrived at from CMB spectral distortion.
Lyman-α forest data are known to be a good probe of the small scale matter power. In this paper, we explore the redshift evolution of the observable effective optical depth τeff (z) from the Lyman-α ...data as a discriminator between dark matter models that differ from the ΛCDM model on small scales. We consider the thermal warm dark matter (WDM) and the ultra-light axion (ULA) models for the following set of parameters: the mass of ULA, ma ≃ 10-24–5 × 10-22 eV and WDM mass, m_ wdm = 0.1 – 4.6 keV. We simulate the line-of-sight HI density and velocity fields using semi-analytic methods. The simulated effective optical depth for the alternative dark matter models diverges from the ΛCDM model for z ≳ 3, which provides a meaningful probe of the matter power at small scales. Using likelihood analysis, we compare the simulated data with the high-resolution Lyman-α forest data in the redshift range 2 < z < 4.2. The analysis yields the following 1σ bounds on dark matter masses: m_ wdm > 0.7 keV and m_ a > 2 × 10-23 eV. To further test the efficacy of our proposed method, we simulate synthetic data sets compatible with the ΛCDM model in the redshift range 2 ≤ z ≤ 6.5 and compare with theory. The 1σ bounds obtained are significantly tighter: m_ wdm > 1.5 keV and m_ a > 7 × 10-23 eV. Although our method provides an alternative way of constraining dark matter models, we note that these bounds are weaker than those obtained by high-resolution hydrodynamical simulations.
Abstract
We study the effect of magnetic braking due to a primordial magnetic field in the context of the formation of massive (≳104M⊙) direct-collapse black holes (DCBHs) at high redshifts. Under ...the assumption of axial symmetry, we analytically compute the effect of magnetic braking on the angular momentum of gas collapsing into the potential well of massive dark matter haloes (≃107−9M⊙) which are spun up by gravitational tidal torques. We find that a primordial magnetic field of strength B0 ≃ 0.1 nG (comoving) can remove the initial angular momentum gained by the in-falling gas due to tidal torques, thus significantly lowering the angular momentum barrier to the formation of DCBHs. These magnetic field strengths are consistent with the bounds on primordial fields from astrophysical and cosmological measurements and they are large enough to seed observed galactic magnetic fields.
Abstract The investigation of the theory of inflation beyond the linear order in perturbations is important both for theoretical consistency and potential observables. In the contemporary literature, ...the calculation of modifications to the inflationary scalar power spectrum due to the loops from the higher order interaction terms in the Hamiltonian have led to an interesting discussion regarding the validity of perturbation theory and the robustness of its predictions. Recently, there have been many efforts to examine the contributions to the scalar power spectrum due to the loops arising from the cubic order terms in the action describing the perturbations, specifically in inflationary scenarios that permit an epoch of ultra slow roll (USR). A brief phase of USR during inflation is known to lead to interesting features in the scalar power spectrum which in turn has significant observational consequences, such as the copious production of primordial black holes. In this work, we consider the loop contributions to the scalar power spectrum in a scenario of USR inflation arising due to the quartic order terms in the action describing the scalar perturbations. We compute the loop contributions to the scalar power spectrum due to the dominant term in the action at the quartic order in a scenario wherein a short phase of USR is sandwiched between two stages of slow roll (SR) inflation. We analyze the behaviour of the loop contributions in terms of the parameters that characterize the non-trivial inflationary dynamics, viz. the onset and duration of USR, and the smoothness of transitions between the USR and SR phases. We examine three different cases of the scenario — the late, intermediate and early epochs of USR during inflation, each of which affects the scalar power spectrum over different ranges of wave numbers. In the inflationary scenario involving a late phase of USR, for reasonable choices of the parameters, we show that the loop corrections are negligible for the entire range of wave numbers. In the intermediate case, the contributions from the loops prove to be scale invariant over large scales and, we find that these contributions can amount to 30% of the leading order (i.e. the Gaussian) power spectrum. In the case wherein USR sets in early, we find that the loop contributions could be negative and can dominate the power spectrum at the leading order, which indicates a breakdown of the validity of the perturbative expansion. We discuss the origin of the negative sign and the divergences that arise in the loop contributions to the power spectrum. We conclude with a brief summary and outlook.
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