Galaxy formation and evolution

Abstract:

Abstract Low surface brightness galaxies (LSBs) are an important class of galaxies that allow us to broaden our understanding of galaxy formation and test various cosmological models. We present a survey of low surface brightness galaxies at 0.4 < zphot < 0.8 in the GOODS-S field using JADES data. We model LSB surface brightness profiles, identifying those with $\bar{\mu }_{\rm eff} > 24$ mag arcsec−2 in the F200W JWST/NIRCam filter. We study the spatial distribution, number density, Sérsic profile parameters, and rest-frame colours of these LSBs. We compare the photometrically-derived star formation histories, mass-weighted ages, and dust attenuations of these galaxies with a high surface brightness (HSB) sample at similar redshift and a lower redshift (zphot < 0.4) LSB sample, all of which have stellar masses ≲ 108M⊙. We find that all samples have low star formation (SFR100 ≲ 0.01 M⊙ yr−1). The higher redshift LSBs and HSBs have similar star formation histories which show that the LSBs and HSBs possibly come from the same progenitors at z ≳ 2, though the histories are not well constrained for the LSB samples. The LSBs appear to have minimal dust, with most of our LSB samples showing AV < 1 mag. JWST has pushed our understanding of LSBs beyond the local Universe.

Abstract:

Abstract Accreting systems can launch powerful outflows which interact with the surrounding medium. We combine new radio observations of the accreting neutron star X-ray binary (XRB) Circinus X-1 (Cir X-1) with archival radio observations going back 24 years. The ∼3 pc scale wide-angle radio and X-ray emitting caps found around Cir X-1 are identified as synchrotron emitting shocks with significant proper motion and morphological evolution on decade timescales. Proper motion measurements of the shocks reveal they are mildly relativistic and decelerating, with apparent velocity of 0.14c ± 0.03c at a propagation distance of 2 pc. We demonstrate that these shocks are likely powered by a hidden relativistic (≳ 0.3c) wide-angle conical outflow launched in 1972 ± 3, in stark contrast to known structures around other XRBs formed by collimated jets over 1000s of years. The minimum time-averaged power of the outflow required to produce the observed synchrotron emission is ∼0.1LEdd, while the time-averaged power required for the kinetic energy of the shocks is $\sim 40 \left(\frac{n}{10^{-2} \textrm{cm}^{-3}}\right)L_\textrm{Edd}$, where n is the average ambient medium number density. This reveals the outflow powering the shocks is likely significantly super-Eddington. We measure significant linear polarisation up to 52 ± 6% in the shocks demonstrating the presence of an ordered magnetic field of strength ∼200 μG. We show that the shocks are potential PeVatrons, capable of accelerating electrons to ∼0.7 PeV and protons to ∼20 PeV, and we estimate the injection and energetic efficiencies of electron acceleration in the shocks. Finally, we predict that next generation gamma-ray facilities may be able to detect hadronic signatures from the shocks.