2009 (IPP)

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21-cm absorbers at intermediate redshifts
(2009-02-01) Gupta, N.; Srianand, R.; Petitjean, Patrick; et al.
Damped Lyman-α systems (DLAs) seen in the spectra of high-z QSOs allow us to probe the physical conditions in protogalaxies. Our understanding of physical conditions in DLAs at high-z is primarily based on the absorption lines of H2 molecules and ﬁne-structure transitions. Another important way of probing the thermal state of interstellar medium in these systems is by studying the 21-cm absorption in the spectra of background quasars. Here we report the main results of our GMRT survey to search for 21-cm absorption in a representative and unbiased sample of 35 DLA candidates at 1.10≤z≤1.45. Our sample of DLA candidates is drawn from the strong Mg ii systems in SDSS DR5 and has resulted in discovery of 9 new 21-cm absorbers. Prior to our survey only one 21-cm absorber was known in the redshift range: 0.7≤z≤2. This survey has allowed us to investigate the dependence of detectability of 21-cm absorption on the properties of UV absorption lines detected in SDSS spectra and estimate the number per unit redshift of 21-cm absorbers. Our GMRT survey provides a representative sample of systems that can be used in combination with various follow-up observations: (1) for investigating the physical conditions in the absorbing gas using spin temperature (TS) measurements, (2) for investigating the eﬀect of metallicity and dust content on the detectability of 21-cm absorption, (3) for studying the morphology of the absorbing gas and (4) for probing the time evolution of various fundamental constants. Results from the ﬁrst phase of our survey are presented in Gupta et al. (2007). Detailed description of the entire sample and results from the survey are presented in Gupta et al. (2009).
AIGO: a southern hemisphere detector for the worldwide array of ground based interferometric gravitational wave detectors
(2009-10-01) Dhurandhar, Sanjeev; Souradeep, Tarun; Coward, D
This paper describes the proposed AlGO detector for the worldwide array of interferometric gravitational wave detectors. The first part of the paper summarises the benefits that AlGO provides to the worldwide array of detectors. The second part gives a technical description of the detector, which will follow closely the Advanced LIGO design. Possible technical variations in the design are discussed.
Anomalous absorption in thioformaldehyde
(2009-10-01) Chandra, Suresh; Kumar, Amit; Sharma, M. K.
Absorption against the Cosmic Microwave Background (CMB), called the anomalous absorption, is an unusual phenomenon. The transition 111 110 at 4.829 GHz of formaldehyde (H2CO) was the rst one showing the anomalous absorption. The c-C3H2 is the second molecule showing anomalous absorption through its transition 220 211 at 21.590 GHz. Structure of thioformaldehyde (H2CS) is very similar to that of the H2CO. Therefore, we have investigated about the physical conditions under which the transition 111 110 at 1.0465 GHz of H2CS would be found in anomalous absorption in cool cosmic objects. As in case of H2CO, the anomalous absorption of 111 110 of H2CS is found sensitive to the relative collisional rates and it requires that the collisional rate for the transition 111 211 must be smaller than that for the transition 110 212.
Assumptions of the primordial spectrum and cosmological parameter estimation
(2009-01-01) Shafieloo, Arman; Souradeep, Tarun
The observables of the perturbed universe, CMB anisotropy and large structures, depend on a set of cosmological parameters, as well as, the assumed nature of primordial perturbations. In particular, the shape of the primordial power spectrum (PPS) is, at best, a well motivated assumption. It is known that the assumed functional form of the PPS in cosmological parameter estimation can aﬀect the best ﬁt parameters and their relative conﬁdence limits. In this letter, we demonstrate that a speciﬁc assumed form actually drives the best ﬁt parameters into distinct basins of likelihood in the space of cosmological parameters where the likelihood resists improvement via modiﬁcations to the PPS. The regions where considerably better likelihoods are obtained allowing free form PPS lie outside these basins. In the absence of a preferred model of inﬂation, this raises a concern that current cosmological parameters estimates are strongly prejudiced by the assumed form of PPS. Our results strongly motivate approaches toward simultaneous estimation of the cosmological parameters and the shape of the primordial spectrum from upcoming cosmological data. It is equally important for theorists to keep an open mind towards early universe scenarios that produce features in the PPS.
Automated star-galaxy segregation using spectral and integrated band data for TAUVEX/ASTROSAT satellite data pipeline
(2009-04-01) Bora, Archana; Harinder, P.; Gupta, Ranjan; et al.
We employ an Artiﬁcial Neural Network (ANN) based technique to develop a pipeline for automated segregation of stars from the galaxies to be observed by Tel-Aviv University Ultra-Violet Experiment (TAUVEX). We use synthetic spectra of stars from UVBLUE library and selected International Ultraviolet Explorer (IUE) low resolution spectra for galaxies in the ultraviolet (UV) region from 1250 to 3220Å as the training set and IUE low-resolution spectra for both the stars and the galaxies as the test set. All the data sets have been pre-processed to get band integrated ﬂuxes so as to mimic the observations of the TAUVEX UV imager. We also perform the ANN based segregation scheme using the full length spectral features (which will also be useful for the ASTROSAT mission). Our results suggest that, in the case of the non-availability of full spectral features, the limited band integrated features can be used to segregate the two classes of objects; although the band data classiﬁcation is less accurate than the full spectral data classiﬁcation.
Bipolar Harmonic encoding of CMB correlation patterns
(2009-12-01) Joshi, Nidhi; Jhingan, S.; Souradeep, Tarun; et al.
Deviations from statistical isotropy can be modeled in various ways, for instance, anisotropic cosmological models (Bianchi models), compact topologies and presence of primordial magnetic ﬁeld. Signature of anisotropy manifests itself in CMB correlation patterns. Here we explore the symmetries of the correlation function and its implications on the observable measures constructed within the Bipolar harmonic formalism for these variety of models. Diﬀerent quantiﬁers within the Bipolar harmonic representation are used to distinguish between plausible models of breakdown of statistical isotropy and as a spectroscopic tool for discriminating between distinct cosmic topology.
CMB Polarization and Temperature Power Spectra Estimation using Linear Combination of WMAP 5-year Maps
(2009-03-01) Souradeep, Tarun; Jain, Pankaj; Saha, Rajib; et al.
We estimate CMB polarization and temperature power spectra using WMAP 5-year foreground contaminated maps. The power spectrum is estimated by using a model independent method, which does not utilize directly the diﬀuse foreground templates nor the detec tor noise model. The method essentially consists of two steps, (i) removal of diﬀuse foregrounds contamination by making linear combination of individual maps in harmonic space and (ii) cross-correlation of foreground cleaned maps to minimize detector noise bias. For temperature power spectrum we also estimate and subtract residual unre- solved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our 1TT, TE and EE power spectra are in good agreement with the published results of the WMAP science team. The error bars on the polarization power spectra, however, turn out to be smaller in comparison to what is obtained by the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We ﬁnd that the bias is small in all cases. A negative bias at low l in TT power spectrum has been pointed in an earlier publication. We ﬁnd that the bias corrected quadrupole power (l(l + 1)Cl/2π) is 532 µK2, approximately 2.5 times the estimate (213.4 µK2) made by the WMAP team.
Complete sample of 21-cm absorbers at z ~ 1.3: Giant Metrewave Radio Telescope Survey Using Mg II Systems
(2009-04-01) Gupta, N.; Srianand, R.; Petitjean, Patrick; et al.
We present the results of a systematic Giant Metrewave Radio Telescope (GMRT) survey of 21-cm absorption in a representative and unbiased sample of 35 strong Mg ii systems in the redshift range: zabs∼1.10−1.45, 33 of which have Wr ≥1˚ A. The survey using ∼400 hrs of telescope time has resulted in 9 new 21-cm detections and stringent 21-cm optical depth upper limits (median 3σ optical depth per 10 kms−1 of 0.017) for the remaining 26 systems. This is by far the largest number of 21-cm detections from any single survey of intervening absorbers. Prior to our survey no intervening 21-cm system was known in the above redshift range and only one system was known in the redshift range 0.7 ≤ z ≤ 1.5. We discuss the relation between the detectability of 21-cm absorption and various properties of UV absorption lines. We show that if Mg ii systems are selected with the following criteria, Mg ii doublet ratio ≤1.3 and Wr(Mg i)/Wr(Mg ii) ≥ 0.3, then a detection rate of 21-cm absorption up to 90% can be achieved. We estimate n21, the number per unit redshift of 21-cm absorbers with Wr(Mg ii) > Wo and integrated optical depth T21 > To and show that n21 decreases with increasing redshift. In particular, for Wo = 1.0 ˚ A and To > 0.3 km s−1, n21 falls by a factor 4 from < z > = 0.5 to < z > = 1.3. The evolution seems to be stronger for stronger Mg ii systems. Using a subsample of systems for which high frequency VLBA images are available, we show that the eﬀect is not related to the structure of the background radio sources and is most probably due to the evolution of the cold neutral medium ﬁlling factor in Mg ii systems. We ﬁnd no correlation between the velocity spread of the 21-cm absorption feature and Wr(Mg ii) at z ∼ 1.3
Composite grains: Effects of porosity and inclusions on the 10 um silicate feature
(2009-03-01) Vaidya, D.B.; Gupta, Ranjan
We calculate the absorption eﬃciency of the composite grains, made up of host silicate spheroids and inclusions of ices/graphites/or voids, in the spectral region 7.0− 14.0µm The absorption eﬃciencies of the composite spheroidal grains for three axial ratios are computed using the discrete dipole approximation (DDA) as well as using the eﬀective medium approximation & T-Matrix (EMT-Tmatrix) approach. We study the absorption as a function of the volume fraction of the inclusions and porosity. In particular, we study the variation in the 10.0µm feature with the volume fraction of the inclusions and porosity. We then calculate the infrared ﬂuxes for these composite grains and compare the model curves with the average observed IRAS-LRS curve, obtained for several circumstellar dust shells around stars. These results on the composite grains show that the wavelength of the peak absorption shifts and the width of the 10.0µm feature varies with the variation in the volume fraction of the inclusions. The model curves for composite grains with axial ratios not very large (AR∼1.3) and volume fractions of inclusions with f=0.20, and dust temperature of about 250-300◦K , ﬁt the observed emission curves reasonably well.
Constraining fundamental constants of physics with quasar absorption line systems
(2009-08-01) Petitjean, Patrick; Vivek, M.; Mohan, V.; et al.
We report long-slit spectroscopic observations of SDSS J092712+294344 carried-out at the recently commissioned 2m telescope in IUCAA Girawali Observatory, India. This AGN-like source is known to feature three sets of emission lines at zem = 0.6972, 0.7020 and 0.7128. Diﬀerent scenarios such as a recoiling black hole after asymmetric emission of gravitational waves, binary black holes and possible merging systems are proposed for this object. We test these scenarios by comparing our spectra with that fromthe Sloan Digital Sky Survey (SDSS), obtained 4 years prior to our observations. Comparing the redshifts of [Oiii]λλ4960,5008 we put a 3σ limit on the relative acceleration to be less than 32 km s−1 yr −1 between diﬀerent emitting regions. Using the 2D spectra obtained at diﬀerent position angles we show that the [Oiii]λ5008 line from the zem = 0.7128 component is extended beyond the spectral point spread function.We infer the linear extent of this line emitting region is ∼ 8 kpc.We also ﬁnd a tentative evidence for an oﬀset between the centroid of the [Oiii]λ5008 line at zem = 0.7128 and the QSO trace when the slit is aligned at a position angle of 299◦ . This corresponds to the zem = 0.7128 system being at an impact parameter of ∼1 kpc with respect to the zem = 0.6972 in the north west direction. Based on our observations we conclude that the binary black hole model is most unlikely. The spatial extent and the sizes are consistent with both black hole recoil and merging scenarios
Cosmic Microwave Background Bispectrum from Primordial Magnetic Fields on Large Angular Scales
(2009-09-01) Seshadri, T. R.; Subramanian, Kandaswamy
Primordial magnetic ﬁelds lead to non-Gaussian signals in the Cosmic Microwave Background (CMB) even at the lowest order, as magnetic stresses, and the temperature anisotropy they induce, depend quadratically on the magnetic ﬁeld. In contrast, CMB non-Gaussianity due to inﬂationary scalar perturbations arise only as a higher order effect. We propose here a novel probe of stochastic primordial magnetic ﬁelds that exploits the characteristic CMB non-Gaussianity that they induce. In particular, we compute the CMB bispectrum (bl 1 l2 l3)induced by stochastic primordial ﬁelds on large angular scales. We ﬁnd a typical value of l1(l1 + 1)l3(l3 + 1)bl1 l2 l3∼ 10−22, for magnetic ﬁelds of strength B0 ∼ 3 nano Gauss and with a nearly scale invariantmagnetic spectrum. Current observational limits on the bispectrum allow us to set upper limits on B0 ∼ 35 nano Gauss, which can be improved by including other magnetically induced contributions to the bispectrum
Damped and sub-damped Lyman-alpha absorbers in z > 4 QSOs
(2009-10-01) Guimaraes, R.; Petitjean, Patrick
We present the results of a survey for damped (DLA, log N(H i) > 20.3) and sub-damped Lyman-α systems (19.5 < log N(H i) < 20.3) at z > 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 < zem < 6.3. Intermediate resolution (R ∼ 4300) spectra have been obtained with the Echellette Spectrograph and Imager (ESI) mounted on the Keck telescope. A total of 100 systems with log N(H i) > 19.5 are detected of which 40 systems are damped Lyman-α systems for an absorption length of ∆X = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs.We study the evolution with redshift of the cosmological density of the neutral gas and ﬁnd, consistently with previous studies at similar resolution, that ΩDLA,HI decreases at z > 3.5. The overall cosmological evolution of ΩHI shows a peak around this redshift. The H i column density distribution for log N(H i) ≥ 20.3 is ﬁtted, consistently with previous surveys, with a single power-law of index α ∼ -1.8±0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a ﬂattening of the function at lower H i column densities with an index of α ∼ −1.4 for the column density range log N(H i) = 19.5−21. The fraction of H i mass in sub-DLAs is of the order of 30%. The H i column density distribution does not evolve strongly from z ∼ 2.5 to z ∼ 4.5.
Detecting gravitational waves from inspiraling binaries with a network of geographically separated detectors: coherent versus coincident strategies
(2009-10-01) Mukhopadhyay, Himan; Tagoshi, H.; Dhurandhar, Sanjeev; et al.
We compare two strategies of multi-detector detection of compact binary inspiral signals, namely, the coincidence and the coherent for the realistic case of geographically separated detectors. The naive coincident strategy treats the detectors as if they are isolated - compares individual detector statistics with their respective thresholds while the coherent strategy combines the detector network data coherently to obtain a single detection statistic which is then compared with a single threshold. We also consider an enhanced coincidence strategy which is intermediate in the sense that though the individual statistics are added in quadrature and the sum compared with a single threshold, the estimated parameters are also checked for consistency. For simplicity, we consider detector pairs having the same power spectral density of noise, as that of initial LIGO and also assume the noise to be stationary and Gaussian. Further, since we consider the detectors to be widely separated on Earth, we take the instrumental noises to be uncorrelated; the wide separation implicitly means that since the detector arms must lie parallel to the Earth’s surface, the detectors necessarily have diﬀerent orientations. We compare the performances of the methods by plotting the receiver operating characteristics (ROC) for the strategies. Several results are derived analytically in order to gain insight. Simulations are performed in order to plot the ROC curves. A single astrophysical source as well as a distribution of sources is considered. We assume one year data train and a mass range of 1 − 40M⊙ for the case of astrophysically distributed sources. We ﬁnd that the coherent strategy is superior to the two coincident strategies that we consider. Remarkably, the detection probability of the coherent strategy is 50% better than the naive coincident strategy. One the other hand, diﬀerence in performance between the coherent strategy and enhanced coincident strategy is not very large. Even in this situation, it is not diﬃcult to perform the real data analysis with the coherent strategy. The bottom line is that the coherent strategy is a good detection strategy.
Diffuse bubble-like radio-halo emission in MRC 0116+111: Imprint of AGN feedback in a distant cluster of galaxies
(2009-02-01) Bagchi, Joydeep
We report the discovery of a luminous, mini radio halo of ∼240 kpc dimension at the center of a distant cluster of galaxies at redshift z = 0.131. Our optical and multi-wavelength GMRT and VLA observations reveal a highly unusual structure showing a twin bubble-like diﬀuse radio halo surrounding a cluster of bright elliptical galaxies; very similar to the large-scale radio structure of M87, the dominant galaxy in Virgo cluster. It presents an excellent opportunity to understand the energetics and the dynamical evolution of such radio jet inﬂated plasma bubbles in the hot cluster atmosphere.
Diffuse molecular gas at high redshift: Detection of CO molecules and the 2175 A* dust feature at z=1.64
(2009-06-01) Noterdaeme, P.; Ledoux, C.; Srianand, R.
We present the detection of carbon monoxide molecules (CO) at z = 1.6408 towards the quasar SDSS J160457.50+220300.5 using the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph. CO absorption is detected in at least two components in the ﬁrst six A-X bands and one d-X(5-0) inter-band system. This is the second detection of this kind along a quasar line of sight. The CO absorption proﬁles are well modelled assuming a rotational excitation of CO in the range 6 < Tex < 16 K, which is consistent with or higher than the temperature of the Cosmic Microwave Background Radiation at this redshift. We derive a total CO column density of N(CO) = 4 × 1014 cm−2 . The measured column densities of S i, Mg i, Zn ii, Fe ii and Si ii indicate a dust depletion pattern typical of cold gas in the Galactic disc. The background quasar spectrum is signiﬁcantly reddened (u−K ∼ 4.5 mag) and presents a pronounced 2175 Å dust absorption feature at the redshift of the CO absorber. Using a control sample of ∼500 quasars we ﬁnd the chance probability for this feature to be spurious is ∼0.3%. We show that the spectral energy distribution (SED) of the quasar is well ﬁtted with a QSO composite spectrum reddened with a Large Magellanic Cloud supershell extinction law at the redshift of the absorber. It is noticeable that this quasar is absent from the colour-selected SDSS quasar sample. This demonstrates our current view of the Universe may be biased against dusty sightlines. These direct observations of carbonaceous molecules and dust open up the possibility of studying physical conditions and chemistry of diﬀuse molecular gas in high redshift galaxies.
Diffuse molecular gas at high redshift: Detection of CO molecules and the 2175 A* dust feature at z=1.64
(2009-06-01) Noterdaeme, P.; Ledoux, C.; Srianand, R.; et al.
We present the detection of carbon monoxide molecules (CO) at z = 1.6408 towards the quasar SDSS J160457.50+220300.5 using the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph. CO absorption is detected in at least two components in the ﬁrst six A-X bands and one d-X(5-0) inter-band system. This is the second detection of this kind along a quasar line of sight. The CO absorption proﬁles are well modelled assuming a rotational excitation of CO in the range 6 < Tex < 16 K, which is consistent with or higher than the temperature of the Cosmic Microwave Background Radiation at this redshift. We derive a total CO column density of N(CO) = 4 × 1014 cm−2 . The measured column densities of S i, Mg i, Zn ii, Fe ii and Si ii indicate a dust depletion pattern typical of cold gas in the Galactic disc. The background quasar spectrum is signiﬁcantly reddened (u−K ∼ 4.5 mag) and presents a pronounced 2175 Å dust absorption feature at the redshift of the CO absorber. Using a control sample of ∼500 quasars we ﬁnd the chance probability for this feature to be spurious is ∼0.3%. We show that the spectral energy distribution (SED) of the quasar is well ﬁtted with a QSO composite spectrum reddened with a Large Magellanic Cloud supershell extinction law at the redshift of the absorber. It is noticeable that this quasar is absent from the colour-selected SDSS quasar sample. This demonstrates our current view of the Universe may be biased against dusty sightlines. These direct observations of carbonaceous molecules and dust open up the possibility of studying physical co
Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7
(2009-08-01) Noterdaeme, P.; Vivek, M.; Mohan, V.
We present the results of a search for damped Lyman-α (DLA) systems in the Sloan Digital Sky Survey II (SDSS), Data Release 7.We use a fully automatic procedure to identify DLAs and derive their column densities. The procedure is checked against the results of previous searches for DLAs in SDSS.We discuss the agreements and diﬀerences and show the robustness of our procedure. For each system, we obtain an accurate measurement of the absorber’s redshift, the Hi column density and the equivalent width of associated metal absorption lines, without any human intervention. We ﬁnd 1426 absorbers with 2.15 < z < 5.2 with log N(Hi) ≥ 20, out of which 937 systems have log N(Hi) ≥ 20.3. This is the largest DLA sample ever built, made available to the scientiﬁc community through the electronic version of this paper. In the course of the survey, we discovered the intervening DLA with highest Hi column density known to date with log N(Hi) = 22.0 ± 0.1. This single system provides a strong constraint on the high-end of the N(Hi) frequency distribution now measured with high accuracy. We show that the presence of a DLA at the blue end of a QSO spectrum can lead to important systematic errors and propose a method to avoid them. This has important consequences for the measurement of the cosmological mass density of neutral gas at z ∼ 2.2 and therefore on our understanding of galaxy evolution over the past 10 billion years. We ﬁnd a signiﬁcant decrease of the cosmological mass density of neutral gas in DLAs, ΩDLA g , from z = 4 to z = 2.2, consistent with the result of previous SDSS studies. However, and contrary to other SDSS studies, we ﬁnd that ΩDLA g (z = 2.2) is about twice the value at z = 0. This implies that ΩDLA g keeps decreasing at z < 2.2.
Features in the primordial power spectrum? A frequentist analysis
(2009-12-01) Hamann, Jan; Shafieloo, Arman; Souradeep, Tarun
Features in the primordial power spectrum have been suggested as an explanation for glitches in the angular power spectrum of temperature anisotropies measured by the WMAP satellite. However, these glitches might just as well be artifacts of noise or cosmic variance. Using the e ective 2 between the best- t power-law spectrum and a deconvolved primordial spectrum as a measure of \featureness" of the data, we perform a full Monte-Carlo analysis to address the question of how signi cant the recovered features are. We nd that in 26% of the simulated data sets the reconstructed spectrum yields a greater improvement in the likelihood than for the actually observed data. While features cannot be categorically ruled out by this analysis, and the possibility remains that simple theoretical models which predict some of the observed features might stand up to rigorous statistical testing, our results suggest that WMAP data are consistent with the assumption of a featureless power-law primordial spectrum.
Giant radio jet of very unusual polarization in a single-lobed radio galaxy
(2009-05-01) Bagchi, Joydeep; Gopal, Krishna; Krause, Marita
We report the discovery of a very unusual, highly asymmetric radio galaxy whose radio jet, the largest yet detected, emits strongly polarized synchrotron radiation and can be traced all the way from the galactic nucleus to the hot spot located ∼ 440 kpc away. This jet emanates from an extremely massive black-hole (> 109M ) and forms a strikingly compact radio lobe. To a surface brightness contrast of at least 15 no radio lobe is detected on the side of the counter-jet, which is similar to the main jet in brightness upto the scale of tens of kpc. Thus, contrary to the nearly universal trend, the brightness asymmetry in this radio galaxy increases with distance from the nucleus. With several unusual properties, including a predominantly toroidal magnetic ﬁeld, this Fanaroﬀ-Riley type II mega-jet is an exceptionally useful laboratory for testing the role of magnetic ﬁeld in jet stabilization and radio lobe formation.
Magnetic quenching of alpha and diffusity tensors in helical turbulence
(2011-07-06) Brandenburg, Axel; Biman, B.; Subramanian, Kandaswamy; et al.
We study the implications of primordial magnetic ﬁelds for the thermal and ionization history of the post-recombination era. In particular we compute the eﬀects of dissipation of primordial magnetic ﬁelds owing to ambipolar diﬀusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing halos and compute the eﬀects of the altered thermal and ionization history on the formation of molecular hydrogen.We show that, for magnetic ﬁeld strengths in the range 2×10−10 G < ∼ B0 < ∼ 2× 10−9 G, the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor 5 to 1000 over the case with no magnetic ﬁelds. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of UV photons and the formation of ﬁrst structures in the universe