by alter-ego » Mon Aug 12, 2019 1:21 am
neufer wrote: ↑Sun Aug 11, 2019 6:13 pm
BDanielMayfield wrote: ↑Sun Aug 11, 2019 3:29 pm
Leon1949Green wrote: ↑Sun Aug 11, 2019 1:23 pm
Regarding the more distant galaxy not interacting with Arp 87. Now that we understand that the disc of our Milky Way is a bit distorted, what is being looked at to determine who we've encountered already to cause it to be that way? Thanks!
Are the Magellanic Clouds massive enough to have caused this warp in the MW?
The problem is their distance (and, to some extent, low angular motion).
Gravitational tidal forces drop off inversely with distance
CUBED.
Solely talking about mass, apparently the MCs masses are enough to perturb the MW plane. However in a recent paper,
ANTLIA2'S ROLE IN DRIVING THE RIPPLES IN THE OUTER GAS DISK OF THE GALAXY, the recently discovered dwarf galaxy,
Antlia 2 is the best candidate collider to produce the observed MW distortions. GAIA measurements (again) have provided trajectory data to feed into to the collision calculations. It is expected the data releases will reduce uncertainties. The authors rule out the Sgr dwarf and both MCs as progenitors.
Paper wrote:In summary, the orbital distributions for Antlia 2 have a signicant tail of low pericenters of 10 kpc for a
range of Milky Way masses commonly cited in the literature (from ~1012to 2x1012M☉).
A close interaction of this kind with a 1:100 mass ratio perturber is sufficient to explain the planar disturbances observed in the outer
HI disk of the Milky Way. Moreover, the phase of the disturbances has a flat radial variation for the HI data,
as do the Antlia 2 simulations with low pericenters, independently confirming that low pericenters are needed
to match the disturbances manifest in the outer gas disk of the Galaxy. We show that the tidal strength of the
Sgr dwarf is insucient to explain the disturbances in the outer gas of the Galaxy. Of the other tidal players of
the Milky Way, the Large and Small Magellanic Clouds are too distant and have not approached closer in the
recent past (Besla et al. 2007; Besla et al. 2012) to account for this level of Fourier power in the outer HI disk.
Thus, Antlia 2 is likely the driver of the observed large perturbations on the outskirts of our Galaxy.
With that said, the progenitor mass is in question:
S&T article wrote:
But not everybody agrees with this conclusion. Vasily Belokurov (University of Cambridge, UK) cites a series of less than probable assumptions required for the Antlia 2 scenario. “Their simulations are rather simple and are produced for one realization of Antlia 2 only,” Belokurov explains. “There are already constraints on the mass of Antlia 2 and at the moment the mass appears lower than what they need.”
I suspect the uncertain contribution from Dark Matter in Antlia 2 is a big factor coupled with the uncertainty in total luminosity due to the poor visibility of this ultra-diffuse galaxy. Maybe improved GAIA data will at least narrow the MW collision zone.
[quote=neufer post_id=294376 time=1565547208 user_id=124483]
[quote=BDanielMayfield post_id=294373 time=1565537393 user_id=139536]
[quote=Leon1949Green post_id=294369 time=1565529801]
Regarding the more distant galaxy not interacting with Arp 87. Now that we understand that the disc of our Milky Way is a bit distorted, what is being looked at to determine who we've encountered already to cause it to be that way? Thanks![/quote]
Are the Magellanic Clouds massive enough to have caused this warp in the MW?[/quote]
The problem is their distance (and, to some extent, low angular motion).
Gravitational tidal forces drop off inversely with distance [b][u]CUBED[/u][/b].
[/quote]
Solely talking about mass, apparently the MCs masses are enough to perturb the MW plane. However in a recent paper, [url=https://arxiv.org/pdf/1906.04203.pdf][i]ANTLIA2'S ROLE IN DRIVING THE RIPPLES IN THE OUTER GAS DISK OF THE GALAXY[/i][/url], the recently discovered dwarf galaxy, [url=https://en.wikipedia.org/wiki/Antlia_2]Antlia 2[/url] is the best candidate collider to produce the observed MW distortions. GAIA measurements (again) have provided trajectory data to feed into to the collision calculations. It is expected the data releases will reduce uncertainties. The authors rule out the Sgr dwarf and both MCs as progenitors. [quote=Paper]In summary, the orbital distributions for Antlia 2 have a signicant tail of low pericenters of 10 kpc for a
range of Milky Way masses commonly cited in the literature (from ~10[sup]12[/sup]to 2x10[sup]12[/sup]M☉).
A close interaction of this kind with a 1:100 mass ratio perturber is sufficient to explain the planar disturbances observed in the outer
HI disk of the Milky Way. Moreover, the phase of the disturbances has a flat radial variation for the HI data,
as do the Antlia 2 simulations with low pericenters, independently confirming that low pericenters are needed
to match the disturbances manifest in the outer gas disk of the Galaxy. [color=#0040FF]We show that the tidal strength of the
Sgr dwarf is insucient to explain the disturbances in the outer gas of the Galaxy. Of the other tidal players of
the Milky Way, the Large and Small Magellanic Clouds are too distant and have not approached closer in the
recent past (Besla et al. 2007; Besla et al. 2012) to account for this level of Fourier power in the outer HI disk.
Thus, Antlia 2 is likely the driver of the observed large perturbations on the outskirts of our Galaxy.[/color][/quote]
With that said, the progenitor mass is in question:
[quote="[url=https://www.skyandtelescope.com/astronomy-news/did-a-dwarf-galaxy-crash-into-the-milky-way/]S&T article[/url]"]
But not everybody agrees with this conclusion. Vasily Belokurov (University of Cambridge, UK) cites a series of less than probable assumptions required for the Antlia 2 scenario. “Their simulations are rather simple and are produced for one realization of Antlia 2 only,” Belokurov explains. “There are already constraints on the mass of Antlia 2 and at the moment the mass appears lower than what they need.”[/quote]
I suspect the uncertain contribution from Dark Matter in Antlia 2 is a big factor coupled with the uncertainty in total luminosity due to the poor visibility of this ultra-diffuse galaxy. Maybe improved GAIA data will at least narrow the MW collision zone.