Constraining the dark matter content of NGC 1291 using hydrodynamic gas response simulations

Abstract

We present a pilot study on the nearby massive barred galaxy NGC 1291, in which we use dynamical modelling to constrain the disc mass-to-light ratio (M/L), thus breaking the degeneracy between the baryonic and dark matter in its central regions. We use the gas, specifically the morphology of the dust lanes on the leading side of the bar, as a tracer of the underlying gravitational potential. We run a large number of hydrodynamic gas response simulations, in potentials obtained directly from near-infrared images of the galaxy, which have three free parameters: the M/L, the bar pattern speed and the height function. We explore the three-dimensional parameter space, by comparing the morphology of the shocks created in the gas response simulations with those of the observed dust lanes, and find the best-fitting models; these suggest that the M/L of NGC 1291 agrees with that predicted by stellar population synthesis models in the near-infrared (≈0.6 M /L ), which leads to a borderline maximum disc for this galaxy. Furthermore, we find that the bar rotates fast, with a corotation radius which is 1.4 times the bar length.

The fraction of dark matter within galaxies from the IllustrisTNG simulations

“…10 and Table 2) is significantly less severe (depending on aperture), yet these models still prefer dark matter density slopes that are NFW rather than contracted. Our DMFs fall among the estimates for generally disc-like galaxies at z = 0 from the two DiskMass and SWELLS samples analysed by Courteau & Dutton (2015) and the Kranz et al (2003); Fragkoudi et al (2017) data -see Fig. 13.…”

“…13, by plotting the DFMs within the simulated 3D stellar half mass radii 8 . We also show the Genzel et al (2017) data, the Courteau & Dutton (2015) DMF derivations for z = 0 galaxies, a modified version of the Courteau & Dutton (2015) SWELLS derivations that uses the Chabrier IMF, and a set of disc observations by Kranz et al (2003) and Fragkoudi et al (2017) that assume different systematics. The data are separated into two panels: the left-hand panel explores some of the systematic uncertainties in the z = 0 observations, and the right-hand panel shows the difference between z = 0 and z = 2.…”

“…Left-hand panel: the DMF of TNG z = 0 discs with the observational results that Courteau & Dutton (2015) derived for the SWELLS (Barnabè et al 2012;Dutton et al 2013) and DiskMass (Martinsson et al 2013a,b) galaxy samples included as blue triangles and pentagons respectively. The Disc DMF measurements of Kranz et al (2003) and Fragkoudi et al (2017) are shown as crossed circles. We also include a version of the SWELLS data in which we change the IMF a posteriori from Salpeter to Chabrier (empty triangles), to make it consistent with our simulation choice.…”

Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

“…We first obtain a stellar mass map for the galaxy from the 3.6µm NIR image, which is cleaned from foreground stars and is deprojected to be face-on (Querejeta et al 2015). To obtain the stellar mass surface density we assign a massto-light ratio of M/L = 0.6 (Meidt et al 2014;Röck et al 2016;Erroz-Ferrer et al 2016;Fragkoudi et al 2017) to each pixel in the NIR image, which has been shown to be suitable for a wide range of ages and metallicities of the underlying stellar populations (Meidt et al 2014). We then assign a height function in order to account for the thickness of the disc (assuming a relation between the scaleheight and scalelength of the galaxy according to Kregel et al 2002), and integrate over the density distribution to obtain the gravitational potential of the disc.…”

“…This function, which has the form f tape (r) = exp((r − r 1 ) 2 )/(2d 2 ) smoothly truncates the gaseous disc for r > r 1 , in order to avoid density discontinuities or numerical issues at the boundary of the simulation box. 6 For more details on this process see Section 4 ofFragkoudi et al 2017 …”