The SPT-Deep Cluster Catalog: Sunyaev-Zel'dovich Selected Clusters from Combined SPT-3G and SPTpol Measurements over 100 Square Degrees (2503.17271v1)

Abstract: We present a catalog of 500 galaxy cluster candidates in the SPT-Deep field: a 100 deg$^2$ field that combines data from the SPT-3G and SPTpol surveys to reach noise levels of 3.0, 2.2, and 9.0 $\mu$K-arcmin at 95, 150, and 220 GHz, respectively. This is comparable to noise levels expected for the wide field survey of CMB-S4, a next-generation CMB experiment. Candidates are selected via the thermal Sunyaev-Zel'dovich (SZ) effect with a minimum significance of $\xi = 4.0$, resulting in a catalog of purity $\sim 89 \%$. Optical data from the Dark Energy Survey and infrared data from the Spitzer Space Telescope are used to confirm 442 cluster candidates. The clusters span $0.12 < z \lesssim 1.8$ and $1.0 \times 10^{14} M_{\odot}/h_{70} < M_{500c} < 8.7 \times 10^{14} M_{\odot}/h_{70}$. The sample's median redshift is 0.74 and the median mass is $1.7 \times 10^{14} M_{\odot}/h_{70}$; these are the lowest median mass and highest median redshift of any SZ-selected sample to date. We assess the effect of infrared emission from cluster member galaxies on cluster selection by performing a joint fit to the infrared dust and tSZ signals by combining measurements from SPT and overlapping submillimeter data from Herschel/SPIRE. We find that at high redshift ($z>1)$, the tSZ signal is reduced by $17.4^{+3.1}_{-2.9} \%$ ($3.7^{+0.7}_{-0.7}\%$) at 150 GHz (95 GHz) due to dust contamination. We repeat our cluster finding method on dust-nulled SPT maps and find the resulting catalog is consistent with the nominal SPT-Deep catalog, demonstrating dust contamination does not significantly impact the SPT-Deep selection function; we attribute this lack of bias to the inclusion of the SPT 220 GHz band.

Analysis of the SPT-Deep Cluster Catalog

The paper, "The SPT-Deep Cluster Catalog: Sunyaev-Zel'dovich Selected Clusters from Combined SPT-3G and SPTpol Measurements over 100 Square Degrees," presents a new galaxy cluster catalog derived from SPT-Deep field data. This field is characterized by combining measurements from the South Pole Telescope's (SPT) third-generation camera (SPT-3G) and the previous generation SPTpol instruments. The paper's primary focus is identifying galaxy clusters using the thermal Sunyaev-Zel'dovich (tSZ) effect over a 100-square-degree region, with an emphasis on the implications for astrophysical and cosmological research.

Key Findings of the Paper

1. Catalog Description: The paper provides a catalog comprising 500 galaxy cluster candidates. These are selected based on tSZ signals, which identify clusters by the interaction of cosmic microwave background (CMB) photons with hot electrons in the intracluster medium. Confirmation of 442 clusters utilizes optical data from the Dark Energy Survey and infrared data from the Spitzer Space Telescope.
2. Data Acquisition and Processing: The paper combines observations from SPT-3G and SPTpol to achieve noise levels comparable to those anticipated for future CMB surveys like CMB-S4. This enables a sensitive probe of clusters across a redshift range of 0.12 to 1.8, with a median redshift of 0.74.
3. Cluster Characteristics: The median mass of clusters is found to be $1.4 \times 10^{14} M_{\odot}/h_{70}$, with the catalog holding the lowest median mass and highest median redshift of any SZ-selected sample to date, highlighting its utility in studying the large-scale structure of the universe.
4. Dust Contamination: The paper addresses potential contamination of the tSZ signal by dust emission from cluster galaxies. Through a joint analysis of mm- and sub-mm wave data, the authors calibrate this contamination's impact on cluster detection, refining the reliability of the tSZ signal as a proxy for cluster mass.
5. Comparison with External Data: The results are compared with other surveys, including the Atacama Cosmology Telescope and the Planck satellite, providing consistent insights regarding the biases in cluster detection due to tSZ variations.

Implications and Future Directions

The SPT-Deep catalog significantly enhances the understanding of cluster populations in the high-redshift universe and the biases inherent in using the tSZ effect for cluster cosmology. Its findings on dust contamination are crucial for future surveys that will extend studies into cosmological parameters, such as the density of matter and dark energy equations of state. This catalog forms a template for future high-precision cosmological studies that aim to explore the nature of dark energy and the evolution of the universe's large-scale structure.

Future work could expand upon these results by integrating data from forthcoming observatories like the Euclid satellite and the Rubin Observatory's Legacy Survey of Space and Time, possibly combining optical and infrared data for a more comprehensive view. Additionally, the methods delineated for handling dust contamination will be vital for interpreting data from these advanced surveys, ensuring the accurate estimation of cosmological parameters across larger cosmic volumes. The SPT-Deep catalog thereby lays the groundwork for an era of cluster cosmology with unprecedented accuracy and scale.