@article{ganjoo_erickcek_lin_mack_2023, title={The effects of relativistic hidden sector particles on the matter power spectrum}, ISSN={["1475-7516"]}, DOI={10.1088/1475-7516/2023/01/004}, abstractNote={Abstract
               If dark matter resides in a hidden sector minimally coupled to the Standard Model, another particle within the hidden sector might dominate the energy density of the early universe temporarily, causing an early matter-dominated era (EMDE). During an EMDE, matter perturbations grow more rapidly than they would in a period of radiation domination, which leads to the formation of microhalos much earlier than they would form in standard cosmological scenarios. These microhalos boost the dark matter annihilation signal, but this boost is highly sensitive to the small-scale cut-off in the matter power spectrum. If the dark matter is sufficiently cold, this cut-off is set by the relativistic pressure of the particle that dominates the hidden sector. We determine the evolution of dark matter density perturbations in this scenario, obtaining the power spectrum at the end of the EMDE. We analyze the suppression of perturbations due to the relativistic pressure of the dominant hidden sector particle and express the cut-off scale and peak scale for which the matter power spectrum is maximized in terms of the properties of this particle. We also supply transfer functions to relate the matter power spectrum with a small-scale cut-off resulting from the pressure of the dominant hidden sector particle to the matter power spectrum that results from a cold hidden sector. These transfer functions facilitate the quick computation of accurate matter power spectra in EMDE scenarios with initially hot hidden sectors and allow us to identify which models significantly enhance the microhalo abundance.
}, number={1}, journal={JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS}, author={Ganjoo, Himanish and Erickcek, Adrienne L. and Lin, Weikang and Mack, Katherine J.}, year={2023}, month={Jan} }
 @article{friedlander_mack_schon_song_vincent_2022, title={Primordial black hole dark matter in the context of extra dimensions}, volume={105}, ISSN={["2470-0029"]}, url={https://doi.org/10.1103/PhysRevD.105.103508}, DOI={10.1103/PhysRevD.105.103508}, abstractNote={Theories of large extra dimensions (LEDs) such as the Arkani-Hamed, Dimopoulos&Dvali scenario predict a"true"Planck scale $M_\star$ near the TeV scale, while the observed $M_{pl}$ is due to the geometric effect of compact extra dimensions. These theories allow for the creation of primordial black holes (PBHs) in the early Universe, from the collisional formation and subsequent accretion of black holes in the high-temperature plasma, leading to a novel cold dark matter (sub)component. Because of their existence in a higher-dimensional space, the usual relationship between mass, radius and temperature is modified, leading to distinct behaviour with respect to their 4-dimensional counterparts. Here, we derive the cosmological creation and evolution of such PBH candidates, including the greybody factors describing their evaporation, and obtain limits on LED PBHs from direct observation of evaporation products, effects on big bang nucleosynthesis, and the cosmic microwave background angular power spectrum. Our limits cover scenarios of 2 to 6 extra dimensions, and PBH masses ranging from 10 to $10^{21}$ g. We find that for two extra dimensions, LED PBHs represent a viable dark matter candidate with a range of possible black hole masses between $10^{17}$ and $10^{23}$ g depending on the Planck scale and reheating temperature. For $M_\star = 10$ TeV, this corresponds to PBH dark matter with a mass of $M \simeq 10^{21}$ g, unconstrained by current observations. We further refine and update constraints on"ordinary"four-dimension black holes.}, number={10}, journal={PHYSICAL REVIEW D}, publisher={American Physical Society (APS)}, author={Friedlander, Avi and Mack, Katherine J. and Schon, Sarah and Song, Ningqiang and Vincent, Aaron C.}, year={2022}, month={May} }
 @article{thomas_trenti_greiner_skrutskie_forbes_klose_mack_mearns_metha_skafidas_et al._2022, title={SkyHopper mission science case I: Identification of high redshift Gamma-Ray Bursts through space-based near-infrared afterglow observations}, volume={39}, ISSN={["1448-6083"]}, DOI={10.1017/pasa.2022.22}, abstractNote={Abstract
	  Long-duration gamma-ray burst (GRB) afterglow observations offer cutting-edge opportunities to characterise the star formation history of the Universe back to the epoch of reionisation, and to measure the chemical composition of interstellar and intergalactic gas through absorption spectroscopy. The main barrier to progress is the low efficiency in rapidly and confidently identifying which bursts are high redshift (
	      
		
		
$z > 5$

	      
	    ) candidates before they fade, as this requires low-latency follow-up observations at near-infrared wavelengths (or longer) to determine a reliable photometric redshift estimate. Since no current or planned gamma-ray observatories carry near-infrared telescopes on-board, complementary facilities are needed. So far this task has been performed by instruments on the ground, but sky visibility and weather constraints limit the number of GRB targets that can be observed and the speed at which follow-up is possible. In this work we develop a Monte Carlo simulation framework to investigate an alternative approach based on the use of a rapid-response near-infrared nano-satellite, capable of simultaneous imaging in four bands from 
	      
		
		
$0.8$

	      
	     to 
	      
		
		
$1.7\,\unicode{x03BC}$

	      
	    m (a mission concept called SkyHopper). Using as reference a sample of 88 afterglows observed with the GROND instrument on the MPG/ESO telescope, we find that such a nano-satellite is capable of detecting in the H-band (1.6 
	      
		
		
$\unicode{x03BC}$

	      
	    m) 
	      
		
		
$72.5\% \pm 3.1\%$

	      
	     of GRBs concurrently observable with the Swift satellite via its UVOT instrument (and 
	      
		
		
$44.1\% \pm 12.3\%$

	      
	     of high redshift (
	      
		
		
$z>5$

	      
	    ) GRBs) within 60 min of the GRB prompt emission. This corresponds to detecting 
	      
		
		
${\sim}55$

	      
	     GRB afterglows per year, of which 1–3 have 
	      
		
		
$z > 5$

	      
	    . These rates represent a substantial contribution to the field of high-z GRB science, as only 23 
	      
		
		
$z > 5$

	      
	     GRBs have been collectively discovered by the entire astronomical community over the last 
	      
		
		
${\sim}24$

	      
	     yr. Future discoveries are critically needed to take advantage of next generation follow-up spectroscopic facilities such as 30m-class ground telescopes and the James Webb Space Telescope. Furthermore, a systematic space-based follow-up of afterglows in the near-infrared will offer new insight on the population of dusty (‘dark’) GRBs which are primarily found at cosmic noon (
	      
		
		
$z\sim 1-3$

	      
	    ). Additionally, we find that launching a mini-constellation of 3 near-infrared nano-satellites would increase the detection fraction of afterglows to 
	      
		
		
${\sim}83\%$

	      
	     and substantially reduce the latency in the photometric redshift determination.}, journal={PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA}, author={Thomas, M. and Trenti, M. and Greiner, J. and Skrutskie, M. and Forbes, Duncan A. and Klose, S. and Mack, K. J. and Mearns, R. and Metha, B. and Skafidas, E. and et al.}, year={2022}, month={Aug} }
 @article{mack_2022, title={The History and Future of the Universe}, url={https://doi.org/10.52750/172163}, DOI={10.52750/172163}, abstractNote={Katie Mack, Ph}, author={Mack, Katherine}, year={2022}, month={Jan} }
 @article{lin_chen_mack_2021, title={Early Universe Physics Insensitive and Uncalibrated Cosmic Standards: Constraints on omega(m) and Implications for the Hubble Tension}, volume={920}, ISSN={["1538-4357"]}, url={https://doi.org/10.3847/1538-4357/ac12cf}, DOI={10.3847/1538-4357/ac12cf}, abstractNote={Abstract
               To further gain insight into whether pre-recombination models can resolve the Hubble tension, we explore constraints on the evolution of the cosmic background that are insensitive to early universe physics. The analysis of the CMB anisotropy has been thought to highly rely on early universe physics. However, we show that the fact that the sound horizon at recombination being close to that at the end of the drag epoch is insensitive to early universe physics. This allows us to link the absolute sizes of the two horizons and treat them as free parameters. Jointly, the CMB peak angular size, baryon acoustic oscillations, and Type Ia supernovae can be used as early universe physics insensitive and uncalibrated cosmic standards, which measure the cosmic history from recombination to today. They can set strong and robust constraints on the post-recombination cosmic background, especially the matter density parameter with Ωm = 0.302 ± 0.008 (68% C.L.), assuming a flat Λ cold dark matter universe after recombination. When we combine these with other nonlocal observations, we obtain several constraints on H
                  0 with significantly reduced sensitivity to early universe physics. These are all more consistent with the Planck 2018 result than the local measurement results such as those based on Cepheids. This suggests a tension between the post-recombination, but nonlocal, observations, and the local measurements that cannot be resolved by modifying pre-recombination early universe physics.}, number={2}, journal={ASTROPHYSICAL JOURNAL}, author={Lin, Weikang and Chen, Xingang and Mack, Katherine J.}, year={2021}, month={Oct} }
 @unpublished{lin_chen_mack_2021, title={Early-Universe-Physics Independent and Uncalibrated Cosmic Standards: Constraint on $\Omega_{\rm{m}}$ and Implications for the Hubble Tension}, journal={arXiv e-prints}, author={Lin, Weikang and Chen, Xingang and Mack, Katherine J.}, year={2021}, month={Feb} }
 @article{cygnus: feasibility of a nuclear recoil observatory with directional sensitivity to dark matter and neutrinos_2020, year={2020}, month={Aug} }
 @article{lin_mack_hou_2020, title={Investigating the Hubble Constant Tension: Two Numbers in the Standard Cosmological Model}, volume={904}, ISSN={["2041-8213"]}, url={https://doi.org/10.3847/2041-8213/abc894}, DOI={10.3847/2041-8213/abc894}, abstractNote={Abstract
               The current Hubble constant tension is usually presented by comparing constraints on H
                  0 only. However, the postrecombination background cosmic evolution is determined by two parameters in the standard ΛCDM model, the Hubble constant (H
                  0) and today’s matter energy fraction (Ωm). If we therefore compare all constraints individually in the H
                  0–Ωm plane, (1) various constraints can be treated as independently as possible, (2) single-sided constraints are easier to consider, (3) compatibility among different constraints can be viewed in a more robust way, (4) the model dependence of each constraint is clear, and (5) whether or not a nonstandard model is able to reconcile all constraints in tension can be seen more effectively. We perform a systematic comparison of different constraints in the H
                  0–Ωm space based on a flat ΛCDM model, treating them as separately as possible. Constraints along different degeneracy directions consistently overlap in one region of the space, with the local measurement from Cepheid variable–calibrated supernovae being the most outlying, followed by the time-delay strong-lensing result. Considering the possibility that some nonstandard physics may reconcile the constraints, we provide a general discussion of nonstandard models with modifications at high, mid, or low redshifts and the effect of local environmental factors. Due to the different responses of individual constraints to a modified model, it is not easy for nonstandard models to reconcile all constraints if none of them have unaccounted-for systematic effects.}, number={2}, journal={ASTROPHYSICAL JOURNAL LETTERS}, author={Lin, Weikang and Mack, Katherine J. and Hou, Liqiang}, year={2020}, month={Dec} }
 @article{mack_kruszelnicki_randall_wade_al-khalili_vedral_2020, title={Reaching out}, volume={2}, ISSN={["2522-5820"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85085180323&partnerID=MN8TOARS}, DOI={10.1038/s42254-020-0185-5}, abstractNote={In the midst of the COVID-19 pandemic, science is crucial to inform public policy. At the same time, mistrust of scientists and misinformation about scientific facts are rampant. Six scientists, actively involved in outreach, reflect on how to build a better understanding and trust of science. In the midst of the COVID-19 pandemic, science is crucial to inform public policy. At the same time, mistrust of scientists and misinformation about scientific facts are rampant. Six scientists, actively involved in outreach, reflect on how to build a better understanding and trust of science. Katie Mack is a theoretical astrophysicist exploring a range of questions in cosmology, the study of the universe from beginning to end. She is currently an assistant professor of physics at North Carolina State University. Her first popular book, The End of Everything (Astrophysically Speaking), will be out in August. She can be found on Twitter as @AstroKatie. Karl Kruszelnicki is a science generalist, with an enthusiastic public following in Australia. He has frontlined in multiple media for decades. He is writing his 46th book and does half a dozen science Q&A radio shows every week. He is a Fellow in the School of Physics at the University of Sydney. He has degrees in maths and physics, biomedical engineering, medicine and surgery. He can be found on Twitter as @doctorkarl. Lisa Randall studies theoretical particle physics and cosmology at Harvard University. Her research connects theoretical insights to puzzles in our current understanding of the properties and interactions of matter. Additionally, she engages with the public through her popular science books, articles, lectures, and radio and TV appearances. Jess Wade is an excitable scientist with an enthusiasm for equality. By day, she is based in the Department of Chemistry at Imperial College London, where she creates superthin films out of organic electronic materials that emit and absorb circularly polarized light. She spends her evenings editing Wikipedia, working to make the internet less sexist and racist. She can be found on Twitter as @jesswade. Jim Al-Khalili, FRS, is a theoretical physicist, author and broadcaster. He holds a Distinguished Chair in physics at the University of Surrey, where he teaches and conducts his research in nuclear physics and open quantum systems. As well as his popular science writing, he is a regular presenter on TV and hosts the long-running BBC Radio 4 programme, The Life Scientific. His latest book, The World According to Physics, is out now. He can be found on Twitter as @jimalkhalili. Vlatko Vedral is a professor of physics at Oxford and National University of Singapore working on quantum physics. He has received many awards for his work, including the Royal Society Wolfson Research Merit Award and the World Scientific Medal and Prize, and was elected a Fellow of the Institute of Physics in 2017. He gives regular interviews to the media and has written articles for New Scientist, Scientific American and other major newspapers, as well as two popular science books.}, number={6}, journal={NATURE REVIEWS PHYSICS}, author={Mack, Katherine and Kruszelnicki, Karl and Randall, Lisa and Wade, Jessica and Al-Khalili, Jim and Vedral, Vlatko}, year={2020}, month={Jun}, pages={282–284} }
 @article{mack_song_vincent_2020, title={Signatures of microscopic black holes and extra dimensions at future neutrino telescopes}, volume={2020}, ISSN={["1029-8479"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85084043898&partnerID=MN8TOARS}, DOI={10.1007/JHEP04(2020)187}, abstractNote={In scenarios with large extra dimensions (LEDs), the fundamental Planck scale can be low enough that collisions between high-energy particles may produce microscopic black holes. High-energy cosmic neutrinos can carry energies much larger than a PeV, opening the door to a higher energy range than Earth-based colliders. Here, for the first time, we identify a number of unique signatures of microscopic black holes as they would appear in the next generation of large-scale neutrino observatories such as IceCube-Gen2 and the Pacific Ocean Neutrino Explorer. These signatures include new event topologies, energy distributions, and unusual ratios of hadronic-to-electronic energy deposition, visible through Cherenkov light echos due to delayed neutron recombination. We find that the next generation of neutrino telescopes can probe LEDs with a Planck scale up to 6 TeV, though the identification of unique topologies could push their reach even further.}, number={4}, journal={JOURNAL OF HIGH ENERGY PHYSICS}, author={Mack, Katherine J. and Song, Ningqiang and Vincent, Aaron C.}, year={2020}, month={Apr} }
 @book{mack_2020, place={New York}, title={The end of everything : (astrophysically speaking)}, publisher={Scribner}, author={Mack, Katie}, year={2020} }
 @article{mack_mcnees_2019, title={Bounds on extra dimensions from micro black holes in the context of the metastable Higgs vacuum}, volume={99}, ISSN={["2470-0029"]}, url={http://dx.doi.org/10.1103/physrevd.99.063001}, DOI={10.1103/PhysRevD.99.063001}, abstractNote={We estimate the rate at which collisions between ultra-high energy cosmic rays can form small black holes in models with extra dimensions. If recent conjectures about false vacuum decay catalyzed by black hole evaporation apply, the lack of vacuum decay events in our past light cone may place new bounds on the black hole formation rate and thus on the fundamental scale of gravity in these models. For theories with fundamental scale $E_{*}$ above the Higgs instability scale of the Standard Model, we find a lower bound on $E_{*}$ that is within about an order of magnitude of the energy where the cosmic ray spectrum begins to show suppression from the GZK effect. Otherwise, the abundant formation of semiclassical black holes with short lifetimes would likely initiate vacuum decay. Assuming a Higgs instability scale at the low end of the range compatible with experimental data, the excluded range is approximately $10^{17} \,\text{eV} \lesssim E_{*} \leq 10^{18.8}\,\text{eV}$ for theories with $n=1$ extra dimension, narrowing to $10^{17}\,\text{eV} \lesssim E_{*} \leq 10^{18.1}\,\text{eV}$ for $n=6$. These bounds rule out regions of parameter space that are inaccessible to collider experiments, small-scale gravity tests, or estimates of Kaluza-Klein processes in neutron stars and supernovae.}, number={6}, journal={PHYSICAL REVIEW D}, author={Mack, Katherine J. and McNees, Robert}, year={2019}, month={Mar} }
 @article{bertone_croon_amin_boddy_kavanagh_mack_natarajan_opferkuch_schutz_takhistov_et al._2019, title={Gravitational wave probes of dark matter: challenges and opportunities}, volume={7}, journal={arXiv e-prints}, author={Bertone, Gianfranco and Croon, Djuna and Amin, Mustafa A. and Boddy, Kimberly K. and Kavanagh, Bradley J. and Mack, Katherine J. and Natarajan, Priyamvada and Opferkuch, Toby and Schutz, Katelin and Takhistov, Volodymyr and et al.}, year={2019}, month={Jul}, pages={arXiv:1907.10610} }
 @article{gravitational wave probes of dark matter: challenges and opportunities_2019, year={2019}, month={Jul} }
 @article{meade_fluke_cooke_andreoni_pritchard_curtin_bernard_asher_mack_murphy_et al._2017, title={Collaborative Workspaces to Accelerate Discovery}, volume={34}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85019118032&partnerID=MN8TOARS}, DOI={10.1017/pasa.2017.15}, abstractNote={AbstractBy applying a display ecology to the Deeper, Wider, Faster proactive, simultaneous telescope observing campaign, we have shown a dramatic reduction in the time taken to inspect DECam CCD images for potential transient candidates and to produce time-critical triggers to standby telescopes. We also show how facilitating rapid corroboration of potential candidates and the exclusion of non-candidates improves the accuracy of detection; and establish that a practical and enjoyable workspace can improve the experience of an otherwise taxing task for astronomers. We provide a critical road test of two advanced displays in a research context—a rare opportunity to demonstrate how they can be used rather than simply discuss how they might be used to accelerate discovery.}, journal={Publications of the Astronomical Society of Australia}, author={Meade, B. and Fluke, C. and Cooke, J. and Andreoni, I. and Pritchard, T. and Curtin, C. and Bernard, S.R. and Asher, A. and Mack, K.J. and Murphy, M.T. and et al.}, year={2017} }
 @article{schön_mack_wyithe_2017, title={Dark matter annihilation in the circumgalactic medium at high redshifts}, volume={474}, ISSN={0035-8711 1365-2966}, url={http://dx.doi.org/10.1093/mnras/stx2968}, DOI={10.1093/mnras/stx2968}, abstractNote={Annihilating dark matter (DM) models offer promising avenues for future DM detection, in particular via modification of astrophysical signals. However when modelling such potential signals at high redshift the emergence of both dark matter and baryonic structure, as well as the complexities of the energy transfer process, need to be taken into account. In the following paper we present a detailed energy deposition code and use this to examine the energy transfer efficiency of annihilating dark matter at high redshift, including the effects on baryonic structure. We employ the PYTHIA code to model neutralino-like DM candidates and their subsequent annihilation products for a range of masses and annihilation channels. We also compare different density profiles and mass-concentration relations for 10^5-10^7 M_sun haloes at redshifts 20 and 40. For these DM halo and particle models, we show radially dependent ionisation and heating curves and compare the deposited energy to the haloes' gravitational binding energy. We use the "filtered" annihilation spectra escaping the halo to calculate the heating of the circumgalactic medium and show that the mass of the minimal star forming object is increased by a factor of 2-3 at redshift 20 and 4-5 at redshift 40 for some DM models.}, number={3}, journal={Monthly Notices of the Royal Astronomical Society}, publisher={Oxford University Press (OUP)}, author={Schön, S and Mack, K J and Wyithe, J S B}, year={2017}, month={Nov}, pages={3067–3079} }
 @article{us cosmic visions: new ideas in dark matter 2017: community report_2017, year={2017}, month={Jul} }
 @inproceedings{ciardi_inoue_mack_xu_bernardi_2015, title={21-cm forest with the SKA}, url={http://dx.doi.org/10.22323/1.215.0006}, DOI={10.22323/1.215.0006}, abstractNote={An alternative to both the tomography technique and the power spectrum approach is to search for the 21cm forest, that is the 21cm absorption features against high-z radio loud sources caused by the intervening cold neutral intergalactic medium (IGM) and collapsed structures. Although the existence of high-z radio loud sources has not been confirmed yet, SKA-low would be the instrument of choice to find such sources as they are expected to have spectra steeper than their lower-z counterparts. Since the strongest absorption features arise from small scale structures (few tens of physical kpc, or even lower), the 21cm forest can probe the HI density power spectrum on small scales not amenable to measurements by any other means. Also, it can be a unique probe of the heating process and the thermal history of the early universe, as the signal is strongly dependent on the IGM temperature. Here we show what SKA1-low could do in terms of detecting the 21cm forest in the redshift range z = 7.5-15.}, booktitle={Proceedings of Advancing Astrophysics with the Square Kilometre Array — PoS(AASKA14)}, publisher={Sissa Medialab}, author={Ciardi, Benedetta and Inoue, Susumu and Mack, Katherine and Xu, Yidong and Bernardi, Gianni}, year={2015}, month={May} }
 @article{schön_mack_avram_wyithe_barberio_2015, title={Dark matter annihilation in the first galaxy haloes}, volume={451}, ISSN={1365-2966 0035-8711}, url={http://dx.doi.org/10.1093/mnras/stv1056}, DOI={10.1093/mnras/stv1056}, abstractNote={We investigate the impact of energy released from self-annihilating dark matter on heating of gas in the small, high-redshift dark matter halos thought to host the first stars. A SUSY neutralino like particle is implemented as our dark matter candidate. The PYTHIA code is used to model the final, stable particle distributions produced during the annihilation process. We use an analytic treatment in conjunction with the code MEDEA2 to find the energy transfer and subsequent partition into heating, ionizing and Lyman alpha photon components. We consider a number of halo density models, dark matter particle masses and annihilation channels. We find that the injected energy from dark matter exceeds the binding energy of the gas within a $10^5$ - $10^6$ M$_\odot$ halo at redshifts above 20, preventing star formation in early halos in which primordial gas would otherwise cool. Thus we find that DM annihilation could delay the formation of the first galaxies.}, number={3}, journal={Monthly Notices of the Royal Astronomical Society}, publisher={Oxford University Press (OUP)}, author={Schön, S. and Mack, K. J. and Avram, C. A. and Wyithe, J. S. B. and Barberio, E.}, year={2015}, month={Jun}, pages={2840–2850} }
 @inproceedings{koopmans_pritchard_mellema_aguirre_ahn_barkana_van bemmel_bernardi_bonaldi_briggs_et al._2015, title={The Cosmic Dawn and Epoch of Reionisation with SKA}, url={http://dx.doi.org/10.22323/1.215.0001}, DOI={10.22323/1.215.0001}, abstractNote={Concerted effort is currently ongoing to open up the Epoch of Reionization (z ∼15-6) for studies with IR and radio telescopes. Whereas IR detections have been made of sources (Lyman-α emitters, quasars and drop-outs) in this redshift regime in relatively small fields of view, no direct detection of neutral hydrogen, via the redshifted 21-cm line, has yet been established. Such a direct detection is expected in the coming years, with ongoing surveys, and could open up the entire universe from z ∼6-200 for astrophysical and cosmological studies, opening not only the Epoch of Reionization, but also its preceding Cosmic Dawn (z ∼30-15) and possibly even the later phases of the Dark Ages (z ∼200-30). All currently ongoing experiments attempt statistical detections of the 21-cm signal during the Epoch of Reionization, with limited signal-to-noise. Direct imaging, except maybe on the largest (degree) scales at lower redshifts, as well as higher redshifts will remain out of reach. The Square Kilometre Array (SKA) will revolutionize the field, allowing direct imaging of neutral hydrogen from scales of arc-minutes to degrees over most of the redshift range z ∼6-28 with SKA1-LOW, and possibly even higher redshifts with the SKA2-LOW. In this SKA will be unique, and in parallel provide enormous potential of synergy with other upcoming facilities (e.g. JWST). In this chapter we summarize the physics of 21-cm emission, the different phases the universe is thought to go through, and the observables that the SKA can probe, referring where needed to detailed chapters in this volume. This is done within the framework of the current SKA1 baseline design and a nominal CD/EoR straw-man survey, consisting of a shallow, medium-deep and deep survey, the latter probing down to ∼1 mK brightness temperature on arc-minute scales at the end of reionization. Possible minor modifications to the design of SKA1 and the upgrade to SKA2 are discussed, in addition to science that could be done already during roll-out when SKA1 still has limited capabilities and/or core collecting area.}, booktitle={Proceedings of Advancing Astrophysics with the Square Kilometre Array — PoS(AASKA14)}, publisher={Sissa Medialab}, author={Koopmans, Leon and Pritchard, J and Mellema, G and Aguirre, J and Ahn, K and Barkana, R and van Bemmel, I and Bernardi, G and Bonaldi, A and Briggs, F and et al.}, year={2015}, month={May} }
 @article{holwerda_keel_kenworthy_mack_2015, title={The dependence of the A<inf>V</inf> prior for SN Ia on host mass and disc inclination}, volume={451}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84942162743&partnerID=MN8TOARS}, DOI={10.1093/mnras/stv1125}, abstractNote={Type Ia supernovae (SNe Ia) are used as ‘standard candles’ for cosmological distance scales. To fit their light-curve shape–absolute luminosity relation, one needs to assume an intrinsic colour and a likelihood of host galaxy extinction or aconvolution of these, acolour distribution prior. The host galaxy extinction prior is typically assumed to be an exponential drop-off for the current supernova programmes (P(AV) ∝ e −AV /τ0). We explore the validity of this prior using the distribution of extinction values inferred when two galaxies accidentally overlap (an occulting galaxy pair). We correct the supernova luminosity distances from the SDSS-III supernova projects (SDSS-SN) by matching the host galaxies to one of three templates from occulting galaxy pairs based on the host galaxy mass and the AV-bias–prior-scale (τ0) relation from Jha et al. We find that introducing an AV prior that depends on host mass results in lowered luminosity distances for the SDSS-SN on average but it does not reduce the scatter in individual measurements. This points, in our view, to the need for many more occulting galaxy templates to match to SN Ia host galaxies to rule out this possible source of scatter in the SN Ia distance measurements. We match occulting galaxy templates based on both mass and projected radius and we find that one should match by stellar mass first with radius as a secondary consideration. We discuss the caveats of the current approach: the lack of enough radial coverage, the small sample of priors (occulting pairs with HST data), the effect of gravitationally interacting as well as occulting pairs, and whether an exponential distribution is appropriate. Our aim is to convince the reader that a library of occulting galaxy pairs observed with HST will provide sufficient priors to improve (optical) SN Ia measurements to the next required accuracy in cosmology.}, number={3}, journal={Monthly Notices of the Royal Astronomical Society}, author={Holwerda, B.W. and Keel, W.C. and Kenworthy, M.A. and Mack, K.J.}, year={2015}, pages={2390–2398} }
 @inproceedings{ciardi_inoue_mack_xu_bernardi_2014, title={21cm Forest with the SKA}, volume={9-13-June-2014}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84978929471&partnerID=MN8TOARS}, booktitle={Proceedings of Science}, author={Ciardi, B. and Inoue, S. and Mack, K.J. and Xu, Y. and Bernardi, G.}, year={2014} }
 @article{mack_2014, title={Known unknowns of dark matter annihilation over cosmic time}, volume={439}, ISSN={1365-2966 0035-8711}, url={http://dx.doi.org/10.1093/mnras/stu129}, DOI={10.1093/mnras/stu129}, abstractNote={Dark matter self-annihilation holds promise as one of the most robust mechanisms for the identification of the particle responsible for the Universe's missing mass. In this work, I examine the evolution of the dark matter annihilation power produced by smooth and collapsed structures over cosmic time, taking into account uncertainties in the structure of dark matter halos. As we search for observational signatures of annihilation, an understanding of this time evolution will help us to best direct our observational efforts, either with local measurements or investigation of the effects of annihilation on the intergalactic medium at high redshift. As I show in this work, there are several key sources of uncertainty in our ability to estimate the dark matter annihilation from collapsed structures, including: the density profile of dark matter halos; the small-scale cut-off in the dark matter halo mass function; the redshift-dependent mass-concentration relation for small halos; and the particle-velocity dependence of the dark matter annihilation process. Varying assumptions about these quantities can result in annihilation power predictions that differ by several orders of magnitude. These uncertainties must be resolved, through a combination of observation and modeling, before robust estimations of the cosmological annihilation signal can be made.}, number={3}, journal={Monthly Notices of the Royal Astronomical Society}, publisher={Oxford University Press (OUP)}, author={Mack, Katherine J.}, year={2014}, month={Feb}, pages={2728–2735} }
 @inproceedings{koopmans_pritchard_mellema_abdalla_aguirre_ahn_barkana_van bemmel_bernardi_bonaldi_et al._2014, title={The cosmic dawn and epoch of reionization with the square kilometre array}, volume={9-13-June-2014}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84978955020&partnerID=MN8TOARS}, booktitle={Proceedings of Science}, author={Koopmans, L.V.E. and Pritchard, J. and Mellema, G. and Abdalla, F. and Aguirre, J. and Ahn, K. and Barkana, R. and Van Bemmel, I. and Bernardi, G. and Bonaldi, A. and et al.}, year={2014} }
 @article{mack_wyithe_2012, title={Detecting the redshifted 21 cm forest during reionization}, volume={425}, ISSN={0035-8711}, url={http://dx.doi.org/10.1111/j.1365-2966.2012.21561.x}, DOI={10.1111/j.1365-2966.2012.21561.x}, abstractNote={The 21cm forest -- HI absorption features in the spectra of high-redshift radio sources -- can potentially provide a unique probe of the largely neutral intergalactic medium (IGM) during the epoch of reionization. We present simulations of the 21cm forest due to the large scale structure of the reionization-era IGM, including a prescription for x-ray heating and the percolation of photoionization bubbles. We show that, if detected with future instruments such as the Square Kilometer Array (SKA), the 21cm forest can provide a significant constraint on the thermal history of the IGM. Detection will be aided by consideration of the sudden increase in signal variance at the onset of 21cm absorption. If radio foregrounds and the intrinsic source spectra are well understood, the flux decrement over wide bandwidths can also improve detection prospects. Our analysis accounts for the possibility of narrow absorption lines from intervening dense regions, but, unlike previous studies, our results do not depend on their properties. Assuming x-ray heating corresponding to a local stellar population, we estimate that a statistically significant detection of 21cm absorption could be made by SKA in less than a year of observing against a Cygnus A-type source at $z \sim 9$, as opposed to nearly a decade for a significant detection of the detailed forest features. We discuss observational challenges due to uncertainties regarding the abundance of background sources and the strength of the 21cm absorption signal.}, number={4}, journal={Monthly Notices of the Royal Astronomical Society}, publisher={Oxford University Press (OUP)}, author={Mack, Katherine J. and Wyithe, J. Stuart B.}, year={2012}, month={Sep}, pages={2988–3001} }
 @article{mack_2011, title={Axions, inflation and the anthropic principle}, volume={2011}, ISSN={1475-7516}, url={http://dx.doi.org/10.1088/1475-7516/2011/07/021}, DOI={10.1088/1475-7516/2011/07/021}, abstractNote={The QCD axion is the leading solution to the strong-CP problem, a dark matter candidate, and a possible result of string theory compactifications. However, for axions produced before inflation, symmetry-breaking scales of fa≳1012 GeV (which are favored in string-theoretic axion models) are ruled out by cosmological constraints unless both the axion misalignment angle θ0 and the inflationary Hubble scale HI are extremely fine-tuned. We show that attempting to accommodate a high-fa axion in inflationary cosmology leads to a fine-tuning problem that is worse than the strong-CP problem the axion was originally invented to solve. We also show that this problem remains unresolved by anthropic selection arguments commonly applied to the high-fa axion scenario.}, number={07}, journal={Journal of Cosmology and Astroparticle Physics}, publisher={IOP Publishing}, author={Mack, Katherine J}, year={2011}, month={Jul}, pages={021–021} }
 @article{mack_steinhardt_2011, title={Cosmological problems with multiple axion-like fields}, volume={2011}, ISSN={1475-7516}, url={http://dx.doi.org/10.1088/1475-7516/2011/05/001}, DOI={10.1088/1475-7516/2011/05/001}, abstractNote={Incorporating the QCD axion and simultaneously satisfying current constraints on the dark matter density and isocurvature fluctuations requires non-minimal fine-tuning of inflationary parameters or the axion misalignment angle (or both) for Peccei-Quinn symmetry-breaking scales fa > 1012 GeV. To gauge the degree of tuning in models with many axion-like fields at similar symmetry-breaking scales and masses, as may occur in string theoretic models that include a QCD axion, we introduce a figure of merit that measures the fractional volume of allowed parameter space: the product of the slow roll parameter and each of the axion misalignment angles, θ0. For a single axion, 10−11 is needed to avoid conflict with observations. We show that the fine tuning of becomes exponentially more extreme in the case of numerous axion-like fields. Anthropic arguments are insufficient to explain the fine tuning because the bulk of the anthropically allowed parameter space is observationally ruled out by limits on the cosmic microwave background isocurvature modes. Therefore, this tuning presents a challenge to the compatibility of string-theoretic models with light axions and inflationary cosmology.}, number={05}, journal={Journal of Cosmology and Astroparticle Physics}, publisher={IOP Publishing}, author={Mack, Katherine J and Steinhardt, Paul J}, year={2011}, month={May}, pages={001–001} }
 @article{ricotti_ostriker_mack_2008, title={Effect of primordial black holes on the cosmic microwave background and coslogical parameter estimates}, volume={680}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-46249091829&partnerID=MN8TOARS}, DOI={10.1086/587831}, abstractNote={We investigate the effect of nonevaporating primordial black holes (PBHs) on the ionization and thermal history of the universe. X-rays emitted by gas accretion onto PBHs modify the cosmic recombination history, producing measurable effects on the spectrum and anisotropies of the cosmic microwave background (CMB). Using the third-year WMAP data and COBE FIRAS data we improve existing upper limits on the abundance of PBHs with masses >0.1 M☉ by several orders of magnitude. The new upper limits still allow PBHs to be important for the origin of supermassive black holes and ultraluminous X-ray sources. Fitting WMAP3 data with cosmological models that do not allow for nonstandard recombination histories, as produced by PBHs or other early energy sources, may lead to an underestimate of the best-fit values of the amplitude of linear density fluctuations (σ8) and the scalar spectral index (ns). Cosmological parameter estimates are affected because models with PBHs allow for larger values of the Thomson scattering optical depth, whose correlation with other parameters may not be correctly taken into account when PBHs are ignored. Values of τe ∼ 0.2, ns ∼ 1, and σ8 ∼ 0.9 are allowed at 95% CF. This result may relieve recent tension between WMAP3 data and clusters data on the value of σ8. PBHs may increase the primordial molecular hydrogen abundance by up to 2 orders of magnitude, this promoting cooling and star formation. The suppression of galaxy formation due to X-ray heating is negligible for models consistent with the CMB data. Thus, the formation rate of the first galaxies and stars would be enhanced by a population of PBHs.}, number={2}, journal={Astrophysical Journal}, author={Ricotti, M. and Ostriker, J.P. and Mack, K.J.}, year={2008}, pages={829–845} }
 @article{mack_2008, title={In the zone}, volume={96}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-40749119768&partnerID=MN8TOARS}, number={2}, journal={American Scientist}, author={Mack, K.J.}, year={2008}, pages={108–109} }
 @article{primordial black holes in the dark ages: observational prospects for future 21cm surveys_2008, year={2008}, month={May} }
 @article{mack_ostriker_ricotti_2007, title={Growth of structure seeded by primordial black holes}, volume={665}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36649010198&partnerID=MN8TOARS}, DOI={10.1086/518998}, abstractNote={We discuss the possibilities for the growth of primordial black holes (PBHs) via the accretion of dark matter. In agreement with previous works, we find that accretion during the radiation-dominated era does not lead to a significant mass increase. However, during matter domination, PBHs may grow by up to 2 orders of magnitude in mass through the acquisition of large dark matter halos. We discuss the possibility of PBHs being an important component in dark matter halos of galaxies, as well as their potential to explain the ultraluminous X-ray sources (ULXs) observed in nearby galactic disks. We point out that although PBHs are ruled out as the dominant component of dark matter, there is still a great deal of parameter space that is open to their playing a role in the modern-day universe. For example, a primordial halo population of PBHs each at 102.5 M☉, making up 0.1% of the dark matter, grows to 104.5 M☉ via the accumulation of dark matter halos and accounts for ~10% of the dark matter mass by a redshift of z ≈ 30. These intermediate-mass black holes may then "light up" when passing through molecular clouds, becoming visible as ULXs at the present day, or they may form the seeds for supermassive black holes at the centers of galaxies.}, number={2 I}, journal={Astrophysical Journal}, author={Mack, K.J. and Ostriker, J.P. and Ricotti, M.}, year={2007}, pages={1277–1287} }
 @article{mack_wesley_king_2007, title={Observing cosmic string loops with gravitational lensing surveys}, volume={76}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-37649020793&partnerID=MN8TOARS}, DOI={10.1103/PhysRevD.76.123515}, abstractNote={We show that the existence of cosmic strings can be strongly constrained by the next generation of gravitational lensing surveys at radio frequencies. We focus on cosmic string loops, which simulations suggest would be far more numerous than long (horizon-sized) strings. Using simple models of the loop population and minimal assumptions about the lensing cross section per loop, we estimate the optical depth to lensing and show that extant radio surveys such as CLASS have already ruled out a portion of the cosmic string model parameter space. Future radio interferometers, such as LOFAR and especially SKA, may constrain G{mu}/c{sup 2}<10{sup -9} in some regions of parameter space, outperforming current constraints from pulsar timing and the cosmic microwave backgound by up to two orders of magnitude. This method relies on direct detections of cosmic strings, and so is less sensitive to the theoretical uncertainties in string network evolution that weaken other constraints.}, number={12}, journal={Physical Review D - Particles, Fields, Gravitation and Cosmology}, author={Mack, K.J. and Wesley, D.H. and King, L.J.}, year={2007} }
 @article{efstathiou_mack_2005, title={The Lyth bound revisited}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-21244500137&partnerID=MN8TOARS}, DOI={10.1088/1475-7516/2005/05/008}, abstractNote={We investigate the Lyth bound relating the tensor–scalar ratio, r, to the variation of the inflaton field, Δϕ, over the course of inflation. For inflationary models that produce at least 55 e-folds of inflation, there is a correlation between r and Δϕ as anticipated by Lyth, but the scatter around the relationship is huge. However, for inflationary models that satisfy current observational constraints on the scalar spectral index and its first derivative, the Lyth relationship is much tighter. In particular, we find that inflationary models with must have , unless the parameters of the models are finely tuned. Large field variations are generally required if a tensor mode signal is to be detected in any foreseeable cosmic microwave background (CMB) polarization experiment.}, number={5}, journal={Journal of Cosmology and Astroparticle Physics}, author={Efstathiou, G. and Mack, K.J.}, year={2005}, pages={121–128} }
 @article{oh_mack_2003, title={Foregrounds for 21-cm observations of neutral gas at high redshift}, volume={346}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0346267362&partnerID=MN8TOARS}, DOI={10.1111/j.1365-2966.2003.07133.x}, abstractNote={We investigate a number of potential foregrounds for an ambitious goal of future radio telescopes such as the Square Kilometer Array (SKA) and the Low Frequency Array (LOFAR): spatial tomography of neutral gas at high redshift in 21-cm emission. While the expected temperature fluctuations due to unresolved radio point sources is highly uncertain, we point out that free–free emission from the ionizing haloes that reionized the Universe should define a minimal bound. This emission is likely to swamp the expected brightness temperature fluctuations, making proposed detections of the angular patchwork of 21-cm emission across the sky unlikely to be viable. Hα observations with JWST could place an upper bound on the contribution of high-redshift sources to the free–free background. An alternative approach is to discern the topology of reionization from spectral features due to 21-cm emission along a pencil-beam slice. This requires tight control of the frequency-dependence of the beam in order to prevent foreground sources from contributing excessive variance. We also investigate potential contamination by galactic and extragalactic radio recombination lines (RRLs). These are unlikely to be show-stoppers, although little is known about the distribution of RRLs away from the Galactic plane. The mini-halo emission signal is always less than that of the intergalactic medium (IGM), making mini-haloes unlikely to be detectable. If they are seen, it will be only in the very earliest stages of structure formation at high redshift, when the spin temperature of the IGM has not yet decoupled from the cosmic microwave background.}, number={3}, journal={Monthly Notices of the Royal Astronomical Society}, author={Oh, S.P. and Mack, K.J.}, year={2003}, pages={871–877} }