ORCID Profile
0000-0002-0077-1492
Current Organisations
University of Adelaide
,
Geneva University
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Publisher: Springer Science and Business Media LLC
Date: 11-05-2022
DOI: 10.1038/S41586-022-04608-1
Abstract: Bright quasars, powered by accretion onto billion-solar-mass black holes, already existed at the epoch of reionization, when the Universe was 0.5-1 billion years old
Publisher: Oxford University Press (OUP)
Date: 07-06-2022
Abstract: The presence of excess scatter in the Ly-α forest at z ∼ 5.5, together with the existence of sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end of hydrogen reionization. However, low data quality and systematic uncertainties complicate the use of Ly-α transmission as a precision probe of reionization’s end stages. In this paper, we assemble a s le of 67 quasar sightlines at z & 5.5 with high signal-to-noise ratios of & per ≤15 km s−1 spectral pixel, relying largely on the new XQR-30 quasar s le. XQR-30 is a large program on VLT/X-Shooter which obtained deep (SNR & 20 per pixel) spectra of 30 quasars at z & 5.7. We carefully account for systematics in continuum reconstruction, instrumentation, and contamination by d ed Ly-α systems. We present improved measurements of the mean Ly-α transmission over 4.9 & z & 6.1. Using all known systematics in a forward modelling analysis, we find excellent agreement between the observed Ly-α transmission distributions and the homogeneous-UVB simulations Sherwood and Nyx up to z ≤ 5.2 (& σ), and mild tension (∼2.5σ) at z = 5.3. Homogeneous UVB models are ruled out by excess Ly-α transmission scatter at z ≥ 5.4 with high confidence (& .5σ). Our results indicate that reionization-related fluctuations, whether in the UVB, residual neutral hydrogen fraction, and/or IGM temperature, persist in the intergalactic medium until at least z = 5.3 (t = 1.1 Gyr after the big bang). This is further evidence for a late end to reionization.
Publisher: Oxford University Press (OUP)
Date: 02-03-2023
Abstract: Intervening metal absorption lines in the spectra of z ≳ 6 quasars are fundamental probes of the ionization state and chemical composition of circumgalactic and intergalactic gas near the end of the reionization epoch. Large absorber s les are required to robustly measure typical absorber properties and to refine models of the synthesis, transport, and ionization of metals in the early Universe. The Ultimate XSHOOTER legacy survey of quasars at z ∼ 5.8–6.6 (XQR-30) has obtained high signal-to-noise spectra of 30 luminous quasars, nearly quadrupling the existing s le of 12 high quality z ∼ 6 quasar spectra. We use this unprecedented s le to construct a catalogue of 778 systems showing absorption in one or more of Mg ii (360 systems), Fe ii (184), C ii (46), C iv (479), Si iv (127), and N v (13) which span 2 ≲ z ≲ 6.5. This catalogue significantly expands on existing s les of z ≳ 5 absorbers, especially for C iv and Si iv which are important probes of the ionizing photon background at high redshift. The s le is 50 per cent (90 per cent) complete for rest-frame equivalent widths W ≳ 0.03 Å (0.09 Å). We publicly release the absorber catalogue along with completeness statistics and a python script to compute the absorption search path for different ions and redshift ranges. This data set is a key legacy resource for studies of enriched gas from the era of galaxy assembly to cosmic noon, and paves the way for even higher redshift studies with JWST and 30 m-class telescopes.
Publisher: Oxford University Press (OUP)
Date: 02-03-2023
Abstract: Intervening C iv absorbers are key tracers of metal-enriched gas in galaxy haloes over cosmic time. Previous studies suggest that the C iv cosmic mass density ($\\Omega _{\\rm C \\, \\small {IV}}$) decreases slowly over 1.5 $\\lesssim \\, z\\lesssim$ 5 before declining rapidly at z ≳ 5, but the cause of this downturn is poorly understood. We characterize the $\\Omega _{\\rm C \\, \\small {IV}}$ evolution over 4.3 ≲ z ≲ 6.3 using 260 absorbers found in 42 XSHOOTER spectra of z ∼ 6 quasars, of which 30 come from the ESO Large Program XQR-30. The large s le enables us to robustly constrain the rate and timing of the downturn. We find that $\\Omega _{\\rm C \\, \\small {IV}}$ decreases by a factor of 4.8 ± 2.0 over the ∼300 Myr interval between z ∼ 4.7 and ∼5.8. The slope of the column density (log N) distribution function does not change, suggesting that C iv absorption is suppressed approximately uniformly across 13.2 ≤ log N/cm−2 & 15.0. Assuming that the carbon content of galaxy haloes evolves as the integral of the cosmic star formation rate density (with some delay due to stellar lifetimes and outflow travel times), we show that chemical evolution alone could plausibly explain the fast decline in $\\Omega _{\\rm C \\, \\small {IV}}$ over 4.3 ≲ z ≲ 6.3. However, the C iv/C ii ratio decreases at the highest redshifts, so the accelerated decline in $\\Omega _{\\rm C \\, \\small {IV}}$ at z ≳ 5 may be more naturally explained by rapid changes in the gas ionization state driven by evolution of the UV background towards the end of hydrogen reionization.
Publisher: Emerald
Date: 02-2016
DOI: 10.1108/JCOM-06-2015-0046
Abstract: – The purpose of this paper is to analyse an Australian commercial radio talkback show that deployed prank as a strategy to scoop royal news to entertain an Australian audience, often commodified for popularity ratings and sponsorship dollars. – Using textual analysis, the study empirically examined the crisis that followed the 2Day FM’s prank call to the Duchess of Cambridge at King Edward VII Hospital, London. The paper engages with the media-made disaster from the lens of issue and crisis management interrogating social conversations and news stories across three countries, i.e., Australia, Britain and India. – Findings reflect that the media, in this case, radio, far more than any other public entity, is subject to public scrutiny and has a moral obligation to practice with public interest at heart. Both news and social media played crucial roles in the escalation of the crisis that ignited a range of public issues. While social media narratives were abusive, condemning and life-threatening, news stories focused on legality, ethics and privacy. – The prank broadcast invited news and social media attention and raised public concern over the ethics of Australian radio entertainment. Crises, whilst often damaging, contribute to the rethinking and rejuvenation of organisational and professional values and practices. – This project is significant in that it is the first to use a radio talk show as a case to engage with issue and crisis management literature and interrogate radio practice in Australia. Further, the project identifies this crisis as media-made and develops an innovative crisis lifecycle model.
Publisher: SAGE Publications
Date: 16-05-2017
Abstract: This article interrogates the notions of terrorism and Islamophobia in two cultural sites. Deploying case study, the article examines the 15 December 2014 Lindt Café siege in Australia and the 16 December 2014 Army Public School massacre in Pakistan. These sites were selected for comparative analysis due to their concurrence and as concerns surrounding terrorism have been mostly West-centric. Findings show that despite socio-political differences, terror attacks in both states ignited activist movements such as ‘Reclaim Pakistan’ and ‘Reclaim Australia’, with both aiming to eradicate extremism. However, while the former focused on the need to reclaim the country from militants, the latter engaged in hate narratives about Islam and Muslims. Islamophobia was identified in Australia, with Taliban-phobia and rejection of Islamo-fascism in Pakistan, as Pakistanis negotiated their identities in a pluralistic Muslim world. The article suggests the need for both local and global processes that are culturally appropriate to mitigate terrorism.
Publisher: Routledge
Date: 21-10-2022
Publisher: Routledge
Date: 21-10-2022
Publisher: Intellect
Date: 2021
DOI: 10.1386/SAFM_00046_1
Abstract: This article shows how India’s popular Hindi cinema markets celebrity actors to promote films where they only appear in supporting roles. Focusing on promotional images of Shah Rukh Khan and Aishwarya Rai Bachchan from two 2016 Bollywood releases, we consider how ‘studio actions’ build on existing celebrity profiles to entice audiences to films. The combined promotion of these stars’ on- and off-screen personas and their ability to transcend Hindi cinema affords them a base of fans that increases their celebrity status across India, its diasporas and globally. As a marketing strategy, the ‘studio actions’ approach has its antecedents in Hollywood and is clearly aimed at increasing box office revenues. The highly visible inclusion of Khan and Rai on promotional materials creates a ‘buzz’ that reminds audiences of the star’s past successes and hints at the promise of seeing them again for an extended screen time.
Publisher: SAGE Publications
Date: 04-2019
Abstract: Terrorism is not a threat to Western civilisation alone. Drawing on interdisciplinary perspectives and using Pakistan as a case, where the war-on-terror is being fought ceaselessly, analysis was carried out on Pakistan’s mainstream media coverage of, and citizen media reactions to, the December 2014 Peshawar school terror attack where 144 people, mostly children, were killed. Discourse analysis of media texts reflects that Pakistan’s mainstream media was spineless in openly fighting terrorism as it focused on the victims of the attack while camouflaging stories with shahadat-ism (martyrdom). On the other hand, citizen media condemned the Taliban perpetrators and hotly debated the perils of Taliban-ism and Islamo-fascism. Attempts to fight militant Islamism and mitigate terrorism were evident in an emerging citizen sphere where the issue took on new meanings, unlike the West. It is important for journalists to be culturally alert in reporting ‘terrorism’ in the light of the intersections of Islamism.
Publisher: Routledge
Date: 21-10-2022
Publisher: SAGE Publications
Date: 28-11-2018
Abstract: This article presents an empirical analysis of the Australian media representation of terrorism using the 2014 Sydney Lindt Café siege as a case in point to engage with the notion of moral panic. Deploying critical discourse analysis and case study as mixed methods, insights into trans-media narratives and aftermath of the terrifying siege are presented. While news media appeared to collaborate with the Australian right-wing government in the reporting of terrorism, social media posed challenges and raised security concerns for the state. Social media heightened the drama as sites were variously deployed by the perpetrator, activists and concerned members of the public. The lified trans-media association of Muslims with terrorism in Australia and its national and global impact, in terms of the political exclusion of Muslims, are best described in this article in the form of an Islamophobic Moral Panic Model, invented for a rethink of the various stages of its occurrence, intensification and institutionalization.
Publisher: Routledge
Date: 21-10-2022
Publisher: Routledge
Date: 21-10-2022
Publisher: Informa UK Limited
Date: 04-03-2023
Publisher: Oxford University Press (OUP)
Date: 18-05-2023
Abstract: The final phase of the reionization process can be probed by rest-frame UV absorption spectra of quasars at z ≳ 6, shedding light on the properties of the diffuse intergalactic medium within the first Gyr of the Universe. The ESO Large Programme ‘XQR-30: the ultimate XSHOOTER legacy survey of quasars at z ≃ 5.8–6.6’ dedicated ∼250 h of observations at the VLT to create a homogeneous and high-quality s le of spectra of 30 luminous quasars at z ∼ 6, covering the rest wavelength range from the Lyman limit to beyond the Mg ii emission. Twelve quasar spectra of similar quality from the XSHOOTER archive were added to form the enlarged XQR-30 s le, corresponding to a total of ∼350 h of on-source exposure time. The median effective resolving power of the 42 spectra is R ≃ 11 400 and 9800 in the VIS and NIR arm, respectively. The signal-to-noise ratio per 10 km s−1 pixel ranges from ∼11 to 114 at λ ≃ 1285 Å rest frame, with a median value of ∼29. We describe the observations, data reduction, and analysis of the spectra, together with some first results based on the E-XQR-30 s le. New photometry in the H and K bands are provided for the XQR-30 quasars, together with composite spectra whose characteristics reflect the large absolute magnitudes of the s le. The composite and the reduced spectra are released to the community through a public repository, and will enable a range of studies addressing outstanding questions regarding the first Gyr of the Universe.
Publisher: Routledge
Date: 21-10-2022
Publisher: Routledge
Date: 21-10-2022
Location: Switzerland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Saira Ali.