Paulo Montero-Camacho

Paulo Montero-Camacho

Assistant Researcher at Peng Cheng Laboratory, interested in cool (cold and hot) cosmology and astrophysics.

Talks and presentations

Astrophysical challenges in the post-reionization intergalactic medium: relics from cosmic reionizatiion

December 01, 2023

Contributed Talk, 32nd Texas Symposium, Shanghai, China

The high-redshift nature of the post-reionization IGM makes it a promising avenue to constrain the nature of dark matter since nonlinearities are not as prominent as in low-redshift alternatives. Nevertheless, to fully unlock 21 cm intensity mapping and the Lyman-alpha forest, which are the two primary cosmological probes of the post-reionization era; we must first account for their respective responses to the reionization process or otherwise face large biases in the inference of cosmological parameters from current/near-term instruments like DESI and SKA. In this talk, I will explain the origin of the imprints of reionization in both 21 cm intensity mapping and the Lyman-alpha forest, quantify the strength of this novel broadband systematic, and establish their dependence on epoch of reionization and cosmic dawn astrophysics. Furthermore, I will introduce mitigation/separation techniques that allow for unbiased Bayesian inference of cosmological parameters in the post-reionization era.

Nailing down the evolution of the IGM in the post-reionization era through high-resolution simulations

March 07, 2023

Invited Talk, PMO Seminar, Purple Mountain Observatory, Nanjing, China

Cosmic reionization corresponds to the milestone of the Universe where the intergalactic medium transitions from primarily neutral, dark, and cold into mainly ionized, more luminous, and warmer. During this transition, the intergalactic medium is violently heated and ripples from the additional injected energy can be seen millions of years after this milestone. However, estimates of these ripples tend to focus on large scales (a choice that was partially motivated by computational resources). In this talk, I will describe the thermodynamic and hydrodynamic response of the often forgotten intergalactic medium small-scale structure to the reionization process. Furthermore, I will showcase how this response leads to observational “fossils” that can be observed in both current Lyman-alpha forest surveys (e.g. DESI) and near-future 21 cm line intensity mapping experiments (e.g. SKA/PUMA). Likewise, I will highlight the physical gains of this effect as a window into the physics that govern cosmic reionization and the Cosmic dawn, and ultimately as a competitive probe of the nature of dark matter.

Nailing down the evolution of the IGM in the post-reionization era through high-resolution simulations

February 23, 2023

Invited Talk, KIAA-DoA Seminar, Peking University, Beijing, China

Cosmic reionization corresponds to the milestone of the Universe where the intergalactic medium transitions from primarily neutral, dark, and cold into mainly ionized, more luminous, and warmer. During this transition, the intergalactic medium is violently heated and ripples from the additional injected energy can be seen millions of years after this milestone. However, estimates of these ripples tend to focus on large scales (a choice that was partially motivated by computational resources). In this talk, I will describe the thermodynamic and hydrodynamic response of the often forgotten intergalactic medium small-scale structure to the reionization process. Furthermore, I will showcase how this response leads to observational “fossils” that can be observed in both current Lyman-alpha forest surveys (e.g. DESI) and near-future 21 cm line intensity mapping experiments (e.g. SKA/PUMA). Likewise, I will highlight the physical gains of this effect as a window into the physics that govern cosmic reionization and the Cosmic dawn, and ultimately as a competitive probe of the nature of dark matter.

Nailing down the evolution of the IGM in the post-reionization era through high-resolution simulations

February 21, 2023

Invited Talk, Astronomy Colloquium, Beijing Normal University, Beijing, China

Cosmic reionization corresponds to the milestone of the Universe where the intergalactic medium transitions from primarily neutral, dark, and cold into mainly ionized, more luminous, and warmer. During this transition, the intergalactic medium is violently heated and ripples from the additional injected energy can be seen millions of years after this milestone. However, estimates of these ripples tend to focus on large scales (a choice that was partially motivated by computational resources). In this talk, I will describe the thermodynamic and hydrodynamic response of the often forgotten intergalactic medium small-scale structure to the reionization process. Furthermore, I will showcase how this response leads to observational “fossils” that can be observed in both current Lyman-alpha forest surveys (e.g. DESI) and near-future 21 cm line intensity mapping experiments (e.g. SKA/PUMA). Likewise, I will highlight the physical gains of this effect as a window into the physics that govern cosmic reionization and the Cosmic dawn, and ultimately as a competitive probe of the nature of dark matter.

Unveiling the astrophysics of reionization in the post-reionization era

December 01, 2022

Invited Talk, DoA Colloquium, Tsinghua University, Beijing, China

Cosmic reionization is the last major phase transition that our Universe goes through. In this milestone, the intergalactic medium transitions from primarily neutral, dark, and cold into mainly ionized, more luminous, and warmer. However, as exciting as the reionization process surely was, many aspects remain unknown, e.g. what are the sources of the ionizing photons? or what is the timeline of reionization? Current and upcoming telescopes (e.g. JWST and HERA/SKA) will directly probe cosmic reionization; nonetheless, interpretation of said measurements will strongly rely on modeling the surroundings of luminous objects (JWST) or on foreground removal (21 cm). In this talk, I will describe a promising novel method to constrain reionization through its impact on the post-reionization intergalactic medium using two promising probes of this era: the Lyman-alpha forest (e.g. DESI) and 21 cm line intensity mapping (e.g. PUMA/SKA). I will focus on both the astrophysics of reionization as a potential source of bias for cosmological analyses and as a promising new avenue to learn about the astrophysics that governs cosmic reionization and the standard cosmological model. Furthermore, I will showcase the potential of this effect to constrain the nature of dark matter via its exquisite small-scale sensitivity.

Unveiling the astrophysics of reionization in the post-reionization era

April 22, 2022

Invited Talk, SWIFAR Colloquium, Yunnan University, Yunnan, China

Cosmic reionization is the last major phase transition that our Universe goes through. In this milestone, the intergalactic medium transitions from primarily neutral, dark, and cold into mainly ionized, luminous, and warm. However, as exciting as the reionization process surely was, many aspects remain unknown, e.g. what are the sources of the ionizing photons? what is the timeline of reionization? Upcoming telescopes (e.g. JWST and SKA) will help to directly probe cosmic reionization. Nonetheless, interpretation of said measurements will strongly rely on modeling the surroundings of luminous objects (JWST) or on foreground removal (21 cm). In this talk, I will describe a promising novel method to constrain reionization through its impact on the post-reionization intergalactic medium. I will focus on the ability of the Lyman-alpha forest (using DESI) to unveil the astrophysics of reionization in the first part of my talk. In the second part, I will describe how we can unlock the full potential of this new methodology through cross-correlations of different cosmological probes of the post-reionization era. Furthermore, I will showcase the potential of this method to constrain the nature of dark matter via its exquisite small-scale sensitivity.

Unveiling the astrophysics of reionization in the post-reionization era

January 12, 2022

Invited Talk, LBNL Colloquium, UC Berkeley, Berkeley, CA, USA

Cosmic reionization is the last major phase transition that our Universe goes through. In this milestone, the intergalactic medium transitions from primarily neutral, dark, and cold into mainly ionized, luminous, and warm. However, as exciting as the reionization process surely was, many aspects remain unknown, e.g. what are the sources of the ionizing photons? what is the timeline of reionization? Upcoming telescopes (e.g. JWST and HERA) will help to directly probe cosmic reionization. Nonetheless, interpretation of said measurements will strongly rely on modeling the surroundings of luminous objects (JWST) or on foreground removal (21 cm). In this talk, I will describe a promising novel method to constrain reionization through its impact in the post-reionization intergalactic medium. I will focus on the ability of the Lyman-alpha forest (using DESI) to unveil the astrophysics of reionization in the first part of my talk. In the second part, I will describe how we can further exploit this new methodology through cross-correlations of different cosmological probes of the post-reionization era. Furthermore, I will showcase the potential of this new methodology to constrain the nature of dark matter via its exquisite small-scale sensitivity.

Constraining the astrophysics of reionization with DESI

October 12, 2021

Contributed Poster, 4th Global 21cm Workshop, online conference, Beijing, China

The impact of reionization on the Lyman-alpha forest power spectrum has recently been shown to be quite significant even at low redshifts (z~2). This memory of reionization survives cosmological time scales because of i) the patchy nature of reionization and ii) underdense regions (i.e. gas in minivoids) which reionize to high entropy and are later compressed (and heated to even larger temperatures) by shocks from denser regions. This effect opens a novel window into the astrophysics of reionization from the post-reionization Universe, which will become online as soon as DESI achieves the near milestone of the first measurement of the 3D Lyman-alpha power spectrum. Here, we forecast, for the first time, the ability of DESI to extract the astrophysics of reionization from the Lyman alpha forest power spectrum. In particular, we found that the 1-sigma errors are 12.2 and 6.91 for the ionization efficiency and threshold mass, respectively. These errors are competitive (but reasonably larger than) previously forecasted errors on the same parameters by using a mock 1000h observation with HERA and SKA. Furthermore, we demonstrate the previously unforeseen ability of DESI to infer the global reionization history, which is naturally worse compared to instruments designed to probe the Epoch of Reionization. Although the performance of DESI is inferior, the prospect for rich cross-correlations due to different systematics is exciting. Besides, DESI may measure the 3D Lyman-alpha power spectrum before the 21cm power spectrum is measured.

Understanding the CMB: from inhomogeneities to that plot you know

August 28, 2021

Invited lecture, alpha-Cen 2021 Summer School, online conference, Beijing, China

The Cosmic Microwave Background (CMB), the frozen photons from when the Universe was approximately 350 thousand years olf, is a gold mine for cosmologists. We have used it to learn about how the Universe started, what are its components, and how it might end. In this talk, I will give a brief overview of where does the CMB comes from, what makes it special, and how to extract information from it.

Constraining the astrophysics of reionization with DESI

May 01, 2021

Contributed Talk, Guo Shoujing Meeting, Hangzhou, China

The impact of reionization on the Lyman-alpha forest power spectrum has recently been shown to be quite significant even at low redshifts (z~2). This memory of reionization survives cosmological time scales because of i) the patchy nature of reionization and ii) underdense regions (i.e. gas in minivoids) which reionize to high entropy and are later compressed (and heated to even larger temperatures) by shocks from denser regions. This effect opens a novel window into the astrophysics of reionization from the post-reionization Universe, which will become online as soon as DESI achieves the near milestone of the first measurement of the 3D Lyman-alpha power spectrum. Here, we forecast, for the first time, the ability of DESI to extract the astrophysics of reionization from the Lyman alpha forest power spectrum. In particular, we found that the 1-sigma errors are 12.2 and 6.91 for the ionization efficiency and threshold mass, respectively. These errors are competitive (but reasonably larger than) previously forecasted errors on the same parameters by using a mock 1000h observation with HERA and SKA. Furthermore, we demonstrate the previously unforeseen ability of DESI to infer the global reionization history, which is naturally worse compared to instruments designed to probe the Epoch of Reionization. Although the performance of DESI is inferior, the prospect for rich cross-correlations due to different systematics is exciting. Besides, DESI may measure the 3D Lyman-alpha power spectrum before the 21cm power spectrum is measured.

Searching the Cosmos: Ripples from Avant-Garde Cosmological Probes

December 07, 2020

Contributed Talk, alpha-Cen 2020 Annual Meeting, online conference, Beijing, China

I will give a brief overview of my research in the field of cosmology. In particular, I will talk very briefly about my research in Primordial Black Holes as dark matter candidates. Furthermore, I will talk about mu current research program on the thermal fossils from hydrogen reionization, and how their ripples from 12.8 billion years ago can help us learn more about how the Universe transitions from mainly neutral to highly ionized. In addition, I will mention the interesting open questions that require further investigation.

Lyman-alpha forest power spectrum as an emerging window into the epoch of reionization and cosmic dawn

November 01, 2020

Contributed Talk, Guo Shoujing Meeting, Zhuhai, Guangdong, China

During cosmic reionization, the IGM is heated by ultraviolet photons sourced primarily by the first stars and galaxies. This extreme heating leaves an imprint in the IGM via disrupting the neutral gas with the injection of thermal energy. The thermal relics, i.e. the disruption to the temperature-density evolution of the IGM due to this imprint, has been recently shown to survive to lower redshifts than previously thought (z~2). In this talk, I will demonstrate that these thermal relics depend on the astrophysics of reionization, thus they can, theoretically, be used to distinguish between different reionization histories. In the second part of the talk, I will show how these thermal relics in the Lyman-alpha forest power spectrum — currently a broadband systematic effect for the Lyman-alpha community —could potentially become a novel window into the epoch of reionization.

Lyman-alpha forest power spectrum as an emerging window into the epoch of reionization and cosmic dawn

July 06, 2020

Recorded Talk, Sazerac, online conference, Beijing, China

The memory of reionization in the Lya forest was recently shown to survive to lower redshifts than previously thought (z~2). This unconventional result originated from carefully tracking the small-scale structure to below jean mass prior to reionization with high-resolution simulations. As a result, one is able to track the HEMD (High-Entropy, Mean-Density) gas in mini-voids, which takes cosmological timescales to relax into the usual-temperature density relation of the IGM. Here, I will show how the memory of inhomogeneous reionization in the Lya forest power spectra — currently a broadband systematic effect for the Lya forest community- could potentially become a window into the Epoch of Reionization.