NASA’s Webb Digs into Structural Origins of Disk Galaxies

Current-day disk galaxies usually comprise a thick, star-filled outer disk and an embedded skinny disk of stars. As an example, our personal Milky Way galaxy’s thick disk is roughly 3,000 light-years in peak, and its skinny disk is roughly 1,000 light-years thick.

How and why does this twin disk construction type? By analyzing archival knowledge from a number of observational applications by NASA’s James Webb Area Telescope, a staff of astronomers is nearer to solutions, in addition to understanding the origins of disk galaxies generally.

The staff fastidiously recognized, visually verified, and analyzed a statistical pattern of 111 edge-on disk galaxies at numerous intervals — as much as 11 billion years in the past (or roughly 2.8 billion years after the massive bang). That is the primary time scientists have investigated thick- and thin-disk constructions spanning such huge distances, bridging the hole between observers probing the early universe and galactic archaeologists looking for to grasp our personal galaxy’s historical past.

“This distinctive measurement of the thickness of the disks at high redshift, or at occasions within the early universe, is a benchmark for theoretical research that was solely potential with Webb,” mentioned Takafumi Tsukui, lead writer of the paper and a researcher on the Australian Nationwide College in Canberra. “Normally, the older, thick disk stars are faint, and the younger, skinny disk stars outshine your complete galaxy. However with Webb’s decision and unique ability to see by means of mud and spotlight faint outdated stars, we will establish the two-disk construction of galaxies and measure their thickness individually.”

By analyzing these 111 targets over cosmological time, the staff was in a position to research single-disk galaxies and double-disk galaxies. Their outcomes point out that galaxies type a thick disk first, adopted by a skinny disk. The timing of when this takes place depends on the galaxy’s mass: high-mass, single-disk galaxies transitioned to two-disk constructions round 8 billion years in the past. In distinction, low-mass, single-disk galaxies shaped their embedded skinny disks afterward, about 4 billion years in the past.

“That is the primary time it has been potential to resolve skinny stellar disks at increased redshift. What’s actually novel is uncovering when skinny stellar disks begin to emerge,” mentioned Emily Wisnioski, a co-author of the paper on the Australian Nationwide College in Canberra. “To see skinny stellar disks already in place 8 billion years in the past, and even earlier, was shocking.”

To clarify this transition from a single, thick disk to a thick and skinny disk, and the distinction in timing for high- and low-mass galaxies, the staff regarded past their preliminary edge-on galaxy pattern and examined knowledge exhibiting fuel in movement from the Atacama Massive Millimeter/submillimeter Array (ALMA) and ground-based surveys.

By considering the movement of the galaxies’ fuel disks, the staff finds their outcomes align with the “turbulent fuel disk” situation, one in all three main hypotheses that has been proposed to clarify the method of thick- and thin-disk formation. On this situation, a turbulent fuel disk within the early universe sparks intense star formation, forming a thick stellar disk. As stars type, they stabilize the fuel disk, which turns into much less turbulent and, in consequence, thinner.

Since large galaxies can extra effectively convert fuel into stars, they settle earlier than their low-mass counterparts, ensuing within the earlier formation of skinny disks. The staff notes that thick- and thin-disk formation should not siloed occasions: The thick disk continues to develop because the galaxy develops, although it’s slower than the skinny disk’s fee of development.

Webb’s sensitivity is enabling astronomers to watch smaller and fainter galaxies, analogous to our personal, at early occasions and with unprecedented readability for the primary time. On this research, the staff famous that the transition interval from thick disk to a thick and skinny disk roughly coincides with the formation of the Milky Method galaxy’s skinny disk. With Webb, astronomers will be capable to additional examine Milky Method-like progenitors — galaxies that may have preceded the Milky Method — which may assist clarify our galaxy’s formation historical past.

Sooner or later, the staff intends to include different knowledge factors into their edge-on galaxy pattern.

“Whereas this research structurally distinguishes skinny and thick disks, there may be nonetheless rather more we want to discover,” mentioned Tsukui. “We need to add the kind of data individuals normally get for close by galaxies, like stellar movement, age, and metallicity. By doing so, we will bridge the insights from galaxies close to and much, and refine our understanding of disk formation.”

These outcomes had been printed within the Monthly Notices of the Royal Astronomical Society.

The James Webb Area Telescope is the world’s premier house science observatory. Webb is fixing mysteries in our photo voltaic system, trying past to distant worlds round different stars, and probing the mysterious constructions and origins of our universe and our place in it. Webb is a world program led by NASA with its companions, ESA (European Area Company) and CSA (Canadian Area Company).

To study extra about Webb, go to:

https://science.nasa.gov/webb