Astronomers detect stars in the most distant galaxies for the first time

Since its launch on December 25, 2021 (quite a Christmas present!), the James Webb Space Telescope (JWST) has taken the sharpest and most detailed form images of the universesurpassing even his predecessor, the venerable hubble space telescope! But what is especially exciting are the types of observations we can expect, where the JWST will use its advanced capabilities to tackle some of the most pressing cosmological mysteries. For example, there is the problem posed by high redshift supermassive black holes (SMBHs) or glowing quasars that existed for the first billion years of the Universe.

To date, astronomers have not been able to determine how SMBHs could have formed so soon after the Big Bang. Part of the problem has been that, until recently, stars in host galaxies with redshift values of Z>2 (within 10.324 billion light-years) have been elusive. But thanks to the JWST, an international team of astronomers recently observed stars in quasars in Z>6 (within 12.716 billion light-years) for the first time. Observations of it could finally allow astronomers to assess the processes in early quasars that governed the formation and evolution of early SMBHs.

The team consisted of astronomers from multiple institutes, universities, and observatories in Japan, China, Europe, the United Kingdom, the United States, Brazil, Taiwan, and Israel. Notable institutions include the Kavli Institutesthe Max–Planck Institutesthe Paris Institute of Astrophysics (IAP), and observatories such as the National Astronomical Observatory of Japan (NAOJ), the W. M. Keck Observatorythe steward observatorythe Leiden Observatory, and others. I study him, “First detections of starlight from quasar host galaxies at z>6”, is being reviewed for publication in the journal Nature.

NIRCam images of the field around J2255+0251 (upper panel) and J2236+0032 (lower panel). Credit: Ding, X. et al. (2022).

Prior to the JWST, observations of high redshift galaxies were limited by data quality and could not provide the high-quality point spread function (PSF) needed. This describes the ability of an optical system to obtain high-resolution, focused images of a distant point light source. To shed some light on the new observations, Universe Today spoke with project leader and lead author Xuheng Ding (Kavli PMU) and co-authors Masafusa Onoue (Kavli PMU/Max Planck Institute for Astronomy) and John D. Silverman (Kavli PMU). /University of Tokyo). As reported via email:

“Basically, to reveal the host galaxy of a quasar, you have to perform the quasar+host image decomposition. The quasar is a point source that is unresolved and can be described by a scaled PSF. Typically, this PSF information comes from single stars in the field of view.

“In addition, the JWST has higher resolution data and can observe the redder wavelength compared to the HST to allow this study to the higher redshift sample. Another advantage of this program is that we proposed to observe the quasar of lower luminosity, which makes it easier to subtract quasar images.”

The quasars they selected for their investigation were J2255+0251 and J2236+0032, two relatively low-luminosity quasars with redshifts of 6.34 and 6.40. This corresponds to a distance of approximately 13.43657 and 13.5637 billion light-years (when the light we see left these objects), or 24.876 and 25.11 billion light-years today. These quasars were first identified as part of a study known as the Subaru High-z Exploring Low Luminosity Quasars (SHELLQ). This survey used the Subaru Telescope’s HSC instrument to observe 162 low-luminosity quasars that existed a billion years after the Big Bang.

These quasars are now the subject of follow-up observations by the JWST program to study high redshift galaxies and observe the stars in their disks for the first time. For their study, the team examined data obtained by the JWST near infrared camera (NIRCam), followed by modeling and glare subtraction from the quasars themselves. They then compared their observations with studies of simulated host quasars at high redshift. The team noted some interesting features about these quasars and their SMBHs that distinguish them from other early galaxies.

Images of four SMBHs captured by the Chandra X-ray Observatory. Credit: X-ray: NASA/CXC Illustration: CXC/M. Weiss

“The results show that the host galaxies of these two quasars are massive and compact,” Ding and colleagues said. “The central positions are offset by quasars, possibly due to uneven dust attenuation or may indicate that these SMBHs are not yet at the center of the gravitational potential well.”

This is similar to recent observations of Z>6 quasar host galaxies that were based on the Atacama Large Millimeter-submillimeter Array (SOUL). These observations also noted offsets in early quasars between the central SMBHs and the surrounding gas, dust, and interstellar stars. The team also notes that these offsets may be due to asymmetries generated by tidal forces, possibly due to galaxy interactions or the accumulation of clumps of cold gas. The team will test these hypotheses in other papers based on JWST data. near infrared spectrograph (NIRSpec) of 12 first quasars. As Ding and his colleagues said:

“The importance of this first paper highlights the tremendous power of JWST and proof that detection of the quasar host at z>6 is possible. Eventually, our program will establish quasar z~6’s first measurements of the host stellar mass and SMBH mass ratio, which will be used to understand its coevolution of the galaxy and its central SMBH. These works will also be useful to understand the origin of SMBH in the early Universe”.

Other reading: arXiv

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