Implications for the Hubble tension from the ages of the oldest astrophysical objects. (arXiv:2105.10421v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Vagnozzi_S/0/1/0/all/0/1">Sunny Vagnozzi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pacucci_F/0/1/0/all/0/1">Fabio Pacucci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Loeb_A/0/1/0/all/0/1">Abraham Loeb</a>
We use the ages of old astrophysical objects (OAO) in the redshift range $0
lesssim z lesssim 8$ as stringent tests of the late-time cosmic expansion
history. Since the age of the Universe at any redshift is inversely
proportional to $H_0$, requiring that the Universe be older than the oldest
objects it contains at any redshift, provides an upper limit on $H_0$. Using a
combination of galaxies imaged from the CANDELS program and various high-$z$
quasars, we construct an age-redshift diagram of $gtrsim 100$ OAO up to $z
sim 8$. Assuming the $Lambda$CDM model at late times, we find the 95%
confidence level upper limit $H_0<73.2,{rm km}/{rm s}/{rm Mpc}$, in slight
disagreement with a host of local $H_0$ measurements. Taken at face value, and
assuming that the OAO ages are reliable, this suggests that ultimately a
combination of pre- and post-recombination ($z lesssim 10$) new physics might
be required to reconcile cosmic ages with early-time and local $H_0$
measurements. In the context of the Hubble tension, our results motivate the
study of either combined global pre- and post-recombination modifications to
$Lambda$CDM, or local new physics which only affects the local $H_0$
measurements.
We use the ages of old astrophysical objects (OAO) in the redshift range $0
lesssim z lesssim 8$ as stringent tests of the late-time cosmic expansion
history. Since the age of the Universe at any redshift is inversely
proportional to $H_0$, requiring that the Universe be older than the oldest
objects it contains at any redshift, provides an upper limit on $H_0$. Using a
combination of galaxies imaged from the CANDELS program and various high-$z$
quasars, we construct an age-redshift diagram of $gtrsim 100$ OAO up to $z
sim 8$. Assuming the $Lambda$CDM model at late times, we find the 95%
confidence level upper limit $H_0<73.2,{rm km}/{rm s}/{rm Mpc}$, in slight
disagreement with a host of local $H_0$ measurements. Taken at face value, and
assuming that the OAO ages are reliable, this suggests that ultimately a
combination of pre- and post-recombination ($z lesssim 10$) new physics might
be required to reconcile cosmic ages with early-time and local $H_0$
measurements. In the context of the Hubble tension, our results motivate the
study of either combined global pre- and post-recombination modifications to
$Lambda$CDM, or local new physics which only affects the local $H_0$
measurements.
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