Origins of ultradiffuse galaxies in the Coma cluster - II. Constraints from their stellar populations

In this second paper of the series we study, with new Keck/DEIMOS spectra, the stellar populations of seven spectroscopically confirmed ultradiffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (similar to 7Gyr), low metallicities ([Z/H] similar to -0.7 dex) and mostly supersolar abundance patterns ([Mg/Fe] similar to 0.13 dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are mostly consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin. However, considering the scatter in the resulting properties and including other UDGs in Coma, together with the results from the velocity phase-space study of the Paper I in this series, a mixed-bag of origins is needed to explain the nature of all UDGs. Our results thus reinforce a scenario in which many UDGs are field dwarfs that become quenched through their later infall onto cluster environments, whereas some UDGs could be genuine primordial galaxies that failed to develop due to an early quenching phase. The unknown proportion of dwarf-like to primordial-like UDGs leaves the enigma of the nature of UDGs still open

Origins of ultradiffuse galaxies in the Coma cluster - I. Constraints from velocity phase space

We use Keck/DEIMOS spectroscopy to confirm the cluster membership of 16 ultradiffuse galaxies (UDGs) in the Coma cluster, bringing the total number of spectroscopically confirmed UDGs from the Yagi et al. (Y16) catalogue to 25. We also identify a new cluster background UDG, confirming that most (similar to 95 per cent) of the UDGs in the Y16 catalogue belong to the Coma cluster. In this pilot study of Coma UDGs in velocity phase space, we find evidence of a diverse origin for Coma cluster UDGs, similar to normal dwarf galaxies. Some UDGs in our sample are consistent with being late infalls into the cluster environment, while some may have been in the cluster for >= 8 Gyr. The late infallen UDGs have higher absolute relative line-of-sight velocities, bluer optical colours, and within the projected cluster core, are smaller in size, compared to the early infalls. The early infall UDGs, which may also have formed in situ, have been in the cluster environment for as long as the most luminous galaxies in the Coma cluster, and they may be failed galaxies that experienced star formation quenching at earlier epochs

Droplet barcoding for massively parallel single-molecule deep sequencing

The ability to accurately sequence long DNA molecules is important across biology, but existing sequencers are limited in read length and accuracy. Here, we demonstrate a method to leverage short-read sequencing to obtain long and accurate reads. Using droplet microfluidics, we isolate, amplify, fragment and barcode single DNA molecules in aqueous picolitre droplets, allowing the full-length molecules to be sequenced with multi-fold coverage using short-read sequencing. We show that this approach can provide accurate sequences of up to 10 kb, allowing us to identify rare mutations below the detection limit of conventional sequencing and directly link them into haplotypes. This barcoding methodology can be a powerful tool in sequencing heterogeneous populations such as viruses

Synthesis and characterization of nanomaterials using microfluidic technology

Nanomaterials have attracted tremendous interest during the past two decades. Microfluidic technology offers an alternative strategy for the synthesis and characterization of nanomaterials with controlled properties. The convergence of nanomaterials and microfluidic technology affords an enormous opportunity for the further development of novel nanomaterials for various applications. This chapter covers recent achievements and the latest trends in the synthesis and characterization of nanomaterials using microfluidic technology