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Baryonic Effects in Galaxy Interactions

Discover how baryonic effects shape galaxy behaviors and clustering.

Matteo Zennaro, Giovanni Aricò, Carlos García-García, Raúl E. Angulo, Lurdes Ondaro-Mallea, Sergio Contreras, Andrina Nicola, Matthieu Schaller, Joop Schaye

― 6 min read


Baryonic Effects Shape Baryonic Effects Shape Galaxies galaxy interactions. Learn how baryonic effects impact
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In the vast universe, galaxies are like curious kids playing with cosmic toys, and scientists, like detectives, are trying to figure out how they interact with each other and the space around them. One of the ways they do this is through Galaxy-galaxy Lensing, where the mass of a galaxy bends the light from a more distant galaxy, acting like a cosmic magnifying glass. But hold on! Just like how a kid’s toy might be shaped by its environment, the way galaxies behave is also influenced by Baryonic Effects—the impact of normal matter (like stars and gas) on their clustering and interactions.

What Are Baryonic Effects?

Imagine you have a big bowl of soup, and as you stir it, the ingredients mix together. In our universe's case, baryons (the stuff that makes up stars, planets, and all the fun things we see) have a stirring influence on the distribution of galaxies and the dark matter holding them together. While dark matter is like the invisible glue of the universe, baryons add a layer of complexity, making things more interesting.

The Galaxy Clustering Mystery

Galaxy clustering is like arranging a bunch of kids in a schoolyard. Some huddle together, while others prefer to play alone. Scientists want to understand why galaxies clump together in certain patterns. They utilize galaxy-galaxy lensing models to study these clustering behaviors. However, things get tricky when baryonic effects enter the picture, mixing things up much like when kids start swapping lunch items during recess.

The Challenge of Modeling

Modeling the interactions and distributions of galaxies should be a straightforward task, right? Well, not quite! The relationship between galaxies and dark matter varies across different scales, and the complexities introduced by baryons make it more challenging. Think of it as trying to build a Lego tower, but kids keep sneaking in and adding their own blocks, changing the design!

Introducing a New Method

In light of these challenges, scientists have proposed a new method to account for baryonic effects in galaxy-galaxy lensing models. This method is akin to giving our Lego tower builders some guidelines and tools to ensure they play nicely with the dark matter blocks.

By employing hydrodynamical simulations, researchers measured how baryons affect the distribution of galaxies. They observed how these normal matter components can significantly change the way galaxies interact. To bring some accuracy into their models, they suggest adding a correction term that accounts for baryons, making the models more robust and reliable.

Baryon Correction Model

The Baryon Correction Model is like a superhero cape for scientists, allowing them to fine-tune their galaxy-galaxy lensing models. By understanding baryonic suppressions (the way baryons modify the matter power spectrum), researchers can create a more accurate picture of how galaxies work together and how they affect one another’s light.

With this model, scientists can achieve astonishing results, predicting how galaxies should behave with 1% accuracy. That’s like hitting a target while blindfolded but still being able to score a bullseye!

The Importance of Simulations

Now, let’s talk about simulations. Imagine playing a video game that represents our universe, where you can tweak the rules and see what happens. Hydrodynamical simulations allow researchers to test different scenarios, tweaking baryonic effects and observing how they change the galaxy’s behavior.

These simulations are crucial because they help scientists develop and validate their models. Just like trying out different recipes to find the best chocolate chip cookie, these simulations let scientists explore various approaches until they strike gold.

Different Baryonic Models

When it comes to baryonic effects, there’s no one-size-fits-all approach. Researchers consider multiple baryonic models, each representing different ways that baryon physics can influence galaxies. Some models may show stronger suppression effects on smaller scales, while others may reflect a gentler interaction.

Comparing these models helps scientists understand the nuances of baryonic physics and how it affects the galaxies’ clustering behavior. It’s like comparing different ice cream flavors—each one has its own unique taste, but together they paint a delicious picture of possibilities.

Selecting Galaxies and Halos

Selecting the right galaxies and halos for study is essential in this field. Researchers gather samples based on specific criteria, such as selecting galaxies with high stellar masses or those with significant star formation rates. This is like putting together a basketball team where you want players with various skills to create a winning combination.

By choosing diverse galaxy samples, scientists can better test their models and ensure they account for the full spectrum of interactions presented in the universe. This selection process ensures they are not just playing around but making valuable discoveries about the cosmos.

The Role of Bayesian Analysis

Now, let’s spice things up with some math! Researchers employ Bayesian analysis to make sense of all the data gathered from their observations and simulations. This approach allows them to update their understanding as new information comes in—like a detective piecing together clues from a mystery.

In this case, scientists analyze how baryonic effects influence the galaxy-matter cross-power spectrum and how these correlations affect inferred parameters. Without proper analysis, they could end up drawing incorrect conclusions about how galaxies behave, which is like trying to solve a puzzle with missing pieces!

The Impact of Baryonic Effects

Ignoring baryonic effects in galaxy-galaxy lensing models can lead to biased results. Researchers found that neglecting these effects can lead to miscalculations in bias parameters, which can have a cascading effect on the overall understanding of galaxy behavior. It’s like attempting to bake a cake without accounting for the oven temperature! The end result can be a disastrous mess.

On the flip side, by incorporating baryonic effects correctly, scientists can obtain more accurate galaxy bias parameters and cosmological insights. This adjustment makes their findings more reliable, leading to a richer understanding of the universe.

Conclusion

In summary, understanding baryonic effects in galaxy-galaxy lensing models is crucial for accurately modeling the behavior of galaxies and their interactions. By developing methods that consider these effects, researchers can improve their models and enhance their findings.

Just remember, the universe is filled with quirks and surprises, much like a game of cosmic hide-and-seek. The more scientists explore these interactions, the more they uncover the wonders of the cosmos. So, let’s keep exploring and maybe one day, we’ll figure out all the cosmic secrets hiding in the depths of space! Who knows, perhaps the universe is just waiting to share its next big surprise!

Original Source

Title: A 1% accurate method to include baryonic effects in galaxy-galaxy lensing models

Abstract: Galaxy clustering and galaxy-galaxy lensing are two of the main observational probes in Stage-IV large-scale structure surveys. Unfortunately, the complicated relationship between galaxies and matter limits the exploitation of this data. Galaxy bias models -- such as the hybrid Lagrangian bias expansion -- allow describing galaxy clustering down to scales as small as $k = 0.7h$/Mpc. However, the galaxy-matter cross-power spectra are already affected by baryons on these scales, directly impacting the modelling of galaxy-galaxy lensing. We propose to extend models of the galaxy-matter cross-power spectrum $P_{\rm gm}(k)$ (currently only accounting for dark matter) by including a baryonic correction inferred from the matter component ($S_{\rm mm}(k)$), so that $P_{\rm gm, full \, physics} (k) = \sqrt{S_{\rm mm}} P_{\rm gm, gravity \, only}$. We use the FLAMINGO simulations to measure the effect of baryons on the galaxy-matter cross-power spectrum and to assess the performance of our model. We perform a Bayesian analysis of synthetic data, implementing a model based on BACCO's hybrid Lagrangian bias expansion (for the nonlinear galaxy bias) and Baryon Correction Model. Ignoring baryons in the galaxy-matter cross-power spectrum leads to a biased inference of the galaxy bias, while ignoring baryons in both the galaxy-matter and matter-matter power spectra leads to a biased inference of both the galaxy bias and cosmological parameters. In contrast, our method is 1% accurate compared to all physics variations in FLAMINGO and on all scales described by hybrid perturbative models ($k < 0.7h$/Mpc). Moreover, our model leads to inferred bias and cosmological parameters compatible within 1$\sigma$ with their reference values. We anticipate that our method will be a promising candidate for analysing forthcoming Stage-IV survey data.

Authors: Matteo Zennaro, Giovanni Aricò, Carlos García-García, Raúl E. Angulo, Lurdes Ondaro-Mallea, Sergio Contreras, Andrina Nicola, Matthieu Schaller, Joop Schaye

Last Update: 2024-12-11 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2412.08623

Source PDF: https://arxiv.org/pdf/2412.08623

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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