A team of astronomers from the University of California, Irvine, and other institutions was among the first to receive data transmissions from the James Webb Space Telescope, and they are using the unprecedentedly clear observations to reveal the secret inner workings of galaxies.
The researchers describe their study of the nearby galaxy NGC 7469 using the JWST’s ultrasensitive mid-infrared detection instruments in a paper published in The Astrophysical Journal Letters. They carried out the most in-depth study yet of the interactions between an active galactic nucleus dominated by a supermassive black hole and the star-forming galaxy regions surrounding it.
“What we’ve seen in this system has taken us by surprise,” said lead author Vivian U, a UCI assistant research scientist in physics and astronomy who was part of one of 13 JWST Early Release Science teams. “When we look at this galaxy from the side, we can see not only winds from the supermassive black hole blowing in our direction, but also ‘shock heating’ of the gas induced by said winds very close to the central active galactic nucleus, which we did not expect to see so clearly.”
The newly realized capability of mid-infrared integral field spectroscopy from the JWST’s Mid-Infrared Instrument now allows us to see not only what’s there behind the dust, but also how things are moving at very small scales that we couldn’t see previously at these wavelengths.
Vivian U
U observed that shock heating occurs when wind from a black hole in the center of a galaxy pushes against surrounding dense gas, forming a shock front that deposits energy into the interstellar medium. According to her, this effect could influence star formation in two opposing ways. It can foster the birth of new stars by compressing the gas into molecular form, or it can prevent birth by destroying stellar nurseries due to excessively strong feedback processes from the galactic wind.
NGC 7469 is a Seyfert galaxy with an active center containing a supermassive black hole and a ring of star-forming regions, according to U. For decades, astronomers have attempted to study the detailed dynamics of these systems, which account for about 10% of all galaxies, but dust – which is commonly abundant at their centers – has made this difficult. The JWST allowed U and her co-authors to see what lies beyond the dust veil.
The researchers were able to map several key ionized and molecular gas emission lines that inform astronomers about the conditions of the interstellar medium — the gas, dust, and radiation that exists between star systems in a galaxy — pinpointing star-forming regions within a starburst ring using the telescope’s 6.5-meter mirror and advanced suite of tools, including the Mid-Infrared Instrument. They also discovered a high-velocity outflow of ionized gas that has been “blueshifted,” which means it is moving toward the observer rather than away.
“The newly realized capability of mid-infrared integral field spectroscopy from the JWST’s Mid-Infrared Instrument now allows us to see not only what’s there behind the dust, but also how things are moving at very small scales that we couldn’t see previously at these wavelengths,” U explained.
“At least in this system, we now have a more coherent picture of how the active galactic nucleus is driving out gas and how that affects the surrounding material,” she added. “We see clear evidence of black hole-driven winds dumping energy into the interstellar medium.”
The fact that NGC 7469 is merging with another galaxy, according to U, is a significant contributor to its roiling dynamics.
“Because of the interaction with another galaxy, galactic materials are being moved around as a result of tidal forces, and they file toward the center of the galaxy system when angular momentum is lost. This process tends to make the galaxy’s core very dusty” She explained. “That’s why you need instruments like the ones aboard the JWST, which allow us to peer through the dust and better understand the dusty cores of merging galaxies.”
The paper published is the first in a series of papers by U and her colleagues analyzing data from the JWST Early Release Science program No. 1328. The spectacular imaging and spectroscopic data from the JWST, according to U, provide an in-depth view of how galaxies evolve through the merging mechanism, allowing her team to delve into the physics of star formation, black hole growth, and feedback in nearby merging galaxies.
