Star Formation Histories from SEDs and CMDs Agree: Evidence for Synchronized Star Formation in Local Volume Dwarf Galaxies over the Past 3 Gyr

Abstract

Star Formation Histories (SFHs) reveal physical processes that influence how galaxies form their stellar mass. We compare the SFHs of a sample of 36 nearby (D 4 Mpc) dwarf galaxies from the ACS Nearby Galaxy Survey Treasury (ANGST), inferred from the Color Magnitude Diagrams (CMDs) of individually resolved stars in these galaxies, with those reconstructed by broad-band Spectral Energy Distribution (SED) fitting using the Dense Basis SED fitting code. When comparing individual SFHs, we introduce metrics for evaluating SFH reconstruction techniques. For both the SED and CMD methods, the median normalized SFH of galaxies in the sample shows a period of quiescence at lookback times of 3-6 Gyr followed by rejuvenated star formation over the past 3 Gyr that remains active until the present day. To determine if these represent special epochs of star formation in the D < 4 Mpc portion of the Local Volume, we break this ANGST dwarf galaxy sample into subsets based on specific star formation rate and spatial location. Modulo offsets between the methods of about 1 Gyr, all subsets show significant decreases and increases in their median normalized SFHs at the same epochs, and the majority of the individual galaxy SFHs are consistent with these trends. These results motivate further study of potential synchronized star formation quiescence and rejuvenation in the Local Volume as well as development of a hybrid method of SFH reconstruction that combines CMDs and SEDs, which have complementary systematics.

The observed cosmic star formation rate density has an evolution which resembles a Γ(a, bt) distribution and can be described successfully by only 2 parameters

“…We note that individual stellar populations can be resolved for nearby objects Olsen et al (2021). using a sample of 36 nearby dwarf galaxies demonstrated a broad agreement between the star formation histories derived from the SEDs and the color magnitude diagrams.…”

A New Hypothesis of Spin Supercurrent as Plausible Mechanism of Biological Nonlocal Interaction, Synchronicity, Quantum Communication

“…Presently, there is a new striking report by Charlotte Olsen et al, proposing that 36 cosmic systems appear to have "facilitated" in a such way that they seem to give synchronized stars arrangement. From Olsen et al paper, they do not give a potential hypothetical explanation [30].…”