A new impossible galaxy

Massive dead disk galaxy challenges theories of galaxy evolution

https://www.sciencedaily.com/release...0621145150.htm

This galaxy (3 times the mass of the milky way) is a compact object
spinning very fast, only 3Gy after the "bang".

Composed of old, yellow stars.

Sure, but excuse me, a star like the sun, yellow, main sequence star, is
5 Gy or more old. All stars in that galaxy (z=2.1) can't be older than
2Gy. To keep things in order, galaxy formation is questioned, but not
the big bang theory.

As these discoveries accumulate, observations start contrdicting theory
in a flagrant way.

Can such an object be build in so little time?

Three times our galaxy mass in a smaller radius, spinning very fast.

[[Mod. note -- The sun is about 4.6 Gy old. See, e.g.
http://solar-center.stanford.edu/FAQ/Qage.html
-- jt]]

On Wednesday, June 21, 2017 at 9:27:03 PM UTC-4, jacobnavia wrote:

Sure, but excuse me, a star like the sun, yellow, main sequence star, is
5 Gy or more old. All stars in that galaxy (z=2.1) can't be older than
2Gy. To keep things in order, galaxy formation is questioned, but not
the big bang theory.

The published paper
( https://arxiv.org/ftp/arxiv/papers/1706/1706.07030.pdf ) gives an
observed spectroscopic age of the galaxy of log[Age(yrs)] = 8.97
(+0.26,-0.25) or between 500 million and 1.7 billion years. This
is comfortably within its cosmological age at a redshift of z=2.15
of 3 billion years.

(Yes, the Sun is currently a 4.6 billion year old yellow main
sequence star. But yellow, main sequence stars can be much younger
than the Sun. For example, 4 billion years ago, the Sun was a
600 million year old yellow main-sequence star.)

--Wayne

Le 22/06/2017 =C3=A0 03:27, jacobnavia a =C3=A9crit :
[[Mod. note -- The sun is about 4.6 Gy old. See, e.g.
http://solar-center.stanford.edu/FAQ/Qage.html
-- jt]]

Yes, but the *whole universe* should have been only 3 billion years old
at this time. Yes there is an error when I said 5 Gy from memory, an
error of 8%.

Instead of pointing to this detail (that has no consequences whatsoever
for my argument) it would have been more interesting to answer how can
4.6 Gy old stars exist in a 3 Gy old universe isn't it?

Thanks for your input in any case.
jacob

On 23/06/2017 04:06, wlandsman wrote:
On Wednesday, June 21, 2017 at 9:27:03 PM UTC-4, jacobnavia wrote:

Sure, but excuse me, a star like the sun, yellow, main sequence star, is
5 Gy or more old. All stars in that galaxy (z=2.1) can't be older than
2Gy. To keep things in order, galaxy formation is questioned, but not
the big bang theory.

The published paper
( https://arxiv.org/ftp/arxiv/papers/1706/1706.07030.pdf ) gives an
observed spectroscopic age of the galaxy of log[Age(yrs)] = 8.97
(+0.26,-0.25) or between 500 million and 1.7 billion years. This
is comfortably within its cosmological age at a redshift of z=2.15
of 3 billion years.

(Yes, the Sun is currently a 4.6 billion year old yellow main
sequence star. But yellow, main sequence stars can be much younger
than the Sun. For example, 4 billion years ago, the Sun was a
600 million year old yellow main-sequence star.)

A bit dimmer when younger but otherwise still main sequence and yellow.

The tricky questions are "why did it stop making new stars?" or put
another way "where did all the dust and gas go?". Swept clean by a
galactic collision perhaps or related to its unusually high spin?

--
Regards,
Martin Brown

Le 23/06/2017 =C3=A0 05:06, wlandsman a =C3=A9crit :
he published paper
(https://arxiv.org/ftp/arxiv/papers/1706/1706.07030.pdf ) gives an
observed spectroscopic age of the galaxy of log[Age(yrs)] = 8.97
(+0.26,-0.25) or between 500 million and 1.7 billion years. This
is comfortably within its cosmological age at a redshift of z=2.15
of 3 billion years.

The paper says:

"The best fitting spectrum reveals a massive, old, post-starburst galaxy
consistent with negligible ongoing star formation, and at most solar
metallicity (that is log(M*/Mo) = 11.15 (+/- 0.23), log[Age(yr)]=8.97
(+/-0.26 0.25), Ai=0.6 (+/- 0.9 0.6)."

*Old* galaxy. I understood that. Now what the log[Age(yr)] = 8.97 that
is a mystery for me. exp(8.9) gives 7331.973. 7331 years ???

I must be doing something very wrong obviously. How do you come from
log(age) = 8.9 to 500 - 1700 million years is also a mystery (for me)

In any case I would like to underscore that we are measuring total light
emission from that galaxy, not looking at any individual star. So it
would have been useful if we would figure out the SPREADING of that
measure. Yes, MOST of the stars would have around 1Gy but there is
certain probability of having stars having 4, or even 5 Gy isn't it?

[[Mod. note -- The authors are likely using base-10 logarithms.
log10[Age(yr) = 8.97 (+0.26 -0.25) gives a range of roughly
500 to 1700 Myr.

It would indeed be useful to know the age distribution of the stars
in that galaxy. But it would surely take a lot more light to
measure that than to measure the integrated properties, i.e.,
compared to the current observations the age-distribution measurement
would need a much larger telescope and/or a much longer exposure time.
-- jt]]

Le 23/06/2017 =C3=A0 05:06, wlandsman a =C3=A9crit :
The published paper
(https://arxiv.org/ftp/arxiv/papers/1706/1706.07030.pdf ) gives an
observed spectroscopic age of the galaxy of log[Age(yrs)] = 8.97
(+0.26,-0.25) or between 500 million and 1.7 billion years. This
is comfortably within its cosmological age at a redshift of z=2.15
of 3 billion years

How can a galaxy 3 times the mass of the milky way (10Gy old at least)
appear in just 2.5 billion years?


Since is 3 times more massive it will attract other galaxies 3 times as
much. If in its environment there are many smaller galaxies, it could
become the big ellipticals that we see today.

But this object is at least as old as our own galaxy since has 3 times
its mass, and a perfect spinning disk structure.

How come that this galaxy has exhausted its gas in just 3Gy?

In the other impossible galaxy that I habe brought to your attention
here, ALMA observations were immediately interpreted as star formation,
meaning that the galaxy was a normal galaxy making stars and not an old one.

The quasar explanation was discarded immediately, that would require
too much time to fit a young universe.

The center of the radiation in ALMA wavelengths was 10 000 light years
away from the center of the visible galaxy. That would fit an
extinguished quasar hypothesis, since that would be the place where the
quasar beam hit the surrounding material and heated it, stopping star
formation by quasar quenching.

But no, we are seeing a normal galaxy making stars obscured by dust. The
dust has a big hole just in synch with our line of sight since we do not
see dust in the visible, Hubble observations. No explanation is
adsvanced for the distance between the visible core and the center of
the ALMA infrared radiation. We suppose another nucleous obscured by
convenient dust.

And now you say that a fast spinning disk of stars, a galaxy 3 times as
massive as our own, can appear suddenly like that?

3 Gy is not a long time in galactic scales. That galaxy makes just 24
turns in that time since our own is making 4 turns/Gy, and that one is
spinning twice as fast.

In my opinion we are seeing what we see: an old galaxy, at least 10Gy
old that has exhausted its gas and could be the precursor of the giant
ellipticals we see today. So, the universe must be at least 23 Gy old.

Note that I use the red shift as a distance measurement even if I do not
think the universe had a bang 13.7 Gy ago. Why is the red shift there?

I do not know.

https://arxiv.org/ftp/arxiv/papers/1706/1706.07030.pdf ) gives an

Now published: Toft et al. 2017 Nature 546, 510.

In article ,
Martin Brown writes:
The tricky questions are "why did it stop making new stars?"

This is a tricky question in general. Many processes for stopping
star formation have been suggested, but their relative importance is
unknown. Probably all of them, and maybe others not yet suggested,
play a role.

In the specific case of MACS J2129.4-0741, the authors suggest that
gas falling into the center of the dark matter halo where the galaxy
resides is shock-heated and therefore too hot to form stars. I am
not convinced this explanation has to be right, but it's plausible.
An active galactic nucleus, which the spectra show is present (but
probably fairly weak at the current epoch), may also be a factor.

or put another way "where did all the dust and gas go?".

Dust is still there. Average visual extinction is about 0.6 mag, and
from reading the image in Fig 3, peak seems to be about 0.9 mag.
Those values are luminosity-weighted, meaning they are probably
underestimates of mass-weighted values. (No knock on the authors;
this is a universal problem with such estimates.)

Swept clean by a galactic collision perhaps

No evidence for a collision, and it's hard to understand how a disk
(which is what this galaxy is) could have survived one.

or related to its unusually high spin?

Not unusually high; the rotation is normal for the galaxy mass. I
don't see how spin would eject dust or gas in any case.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

In article , I wrote:
Many processes for stopping star formation have been suggested,
but their relative importance is unknown.

The 2017 July issue of _Sky & Telescope_ has a good overview of the
subject (p 22, author Keith Cooper). I'd quibble with a few things:
infalling, shock-heated gas is not mentioned, and there's confusion
among radiation pressure, stellar and supernova outflows, and
radiative ionization. Nevertheless, the article gives a good sense
of the knowns and unknowns.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

In article , jacobnavia
writes:

Massive dead disk galaxy challenges theories of galaxy evolution

https://www.sciencedaily.com/release...0621145150.htm

This galaxy (3 times the mass of the milky way) is a compact object
spinning very fast, only 3Gy after the "bang".

Composed of old, yellow stars.

Sure, but excuse me, a star like the sun, yellow, main sequence star, is
5 Gy or more old. All stars in that galaxy (z=2.1) can't be older than
2Gy. To keep things in order, galaxy formation is questioned, but not
the big bang theory.

The idea "red or yellow old, blue young" is misleading. A blue star has
to be young, because they don't live long (main-sequence stars here;
white dwarfs are also "blue" but can be quite old). A yellow star,
however, whatever its age, was also yellow when it was young. If a
POPULATION of stars is yellow, it means a) that all the blue ones have
died or b) that no blue ones ever formed. Considering that we don't
know the IMF, much less how it comes about, one shouldn't jump to
conclusions here.

In other words, stars don't move ALONG the main sequence as they evolve,
at least not significantly.