Hello,

Attached you will find where the Galaxy survey locations are not randomly distributed across the sky; rather, their placement is dictated by observational constraints, which do not necessarily align with the true large-scale structure of the universe. As a result, surveys can introduce artificial patterns of clustering and voids that may misrepresent the actual cosmic distribution of galaxies.

This issue is central to my analysis, which I describe using two distinct observational regions: Region A, where numerous foreground galaxies obscure the view of more distant galaxies, and Region B, where distant galaxies are observed without significant foreground obstruction. The presence of these regions might suggest a striking asymmetry in galaxy distribution, raising the possibility that cosmic expansion may not be uniform in all directions.

If this asymmetry is real, it could explain why measurements of the Hubble constant vary depending on the portion of the sky being observed. This unexpected division of the sky into Region A and Region B calls for a deeper investigation into its origins and potential implications for our cosmological models.

Thanks for your reply. Best JM

There is no real asymmetry in either the SN distribution or galaxy distribution. The latter seems to be mostly the SDSS, so it is limited mostly to the north, because that's where the telescope is. The empty U-shaped region is where the disk of the MIlky Way is, where it is difficult to observe extragalactic objects due to high amount of dust. The difference between N/S for SNe is a consequence of different surveys operating at different positions on the Earth and having different sensitivity and cadence.

In essence, we are convinced that as long we choose large enough part of the sky, the Universe is statistically identical irrespectively which direction we look at.

Thank you for your reply. Indeed, I noticed that among the SN‘s in my table, almost 90% have DEC‘s close to zero. I get the following explanation from ChatGpt:

“Astronomers often observe stars with declinations (DEC) close to zero (near the celestial equator) for several main reasons:

1. Visibility from both hemispheres - stars near DEC = 0 can be seen from both the northern and southern hemispheres, making them accessible to more telescopes around the world. This allows for more collaborative observations and long-term monitoring.

2. Maximum observing time - since the celestial equator passes directly overhead for observers at the Earth's equator, stars near DEC = 0 spend more time above the horizon compared to stars with higher or lower declinations. This results in longer uninterrupted observing times.

3. Better coverage for surveys. Many all-sky surveys (e.g. SDSS, Gaia) aim to cover the sky uniformly. The celestial equator is a natural reference point that provides a balanced data set, reducing observational bias.

4. Milky Way and exoplanet studies. The densest part of the Milky Way, which includes the galactic plane and the galactic center, crosses the celestial equator. Many exoplanet search programs (e.g. TESS, Kepler follow-up programs) prioritize this region because it contains a high concentration of stars.

5. Easier star tracking. For telescopes with equatorial mounts, tracking objects along the celestial equator is often easier because these stars move with a predictable and constant angular velocity across the sky.

Because of these advantages, declination = 0 is a key region for both professional and amateur astronomers.”

Best, JM