Investigating the Dust Distribution in Galactic Disks with Dustpedia and NiKA2
Lead Research Organisation:
CARDIFF UNIVERSITY
Department Name: School of Physics and Astronomy
Abstract
We are currently leading large international collaborations to exploit data
obtained with the Herschel Space Observatory. The data obtained is being
used to study the far-infrared spectral energy distribution of nearby galaxies to
learn more about the physical properties of cosmic dust and the ways in which
galaxies have evolved and changed with time. Having taken the leading role
in one of Herschel's primary instruments the Cardiff instrumentation group are
now leading the development of instruments for ground based telescopes.
One such instrument, the NIKA2 camera, will be deployed on the IRAM
telescope in autumn 2015. Our proposed project concerns the exploitation of
the unique imaging capabilities of this camera , which is designed to observe
at a wavelength of 1 and 2 mm. The project is to specifically use this data
along with our Herschel data to try and understand physical processes in the
inter-stellar medium not previously observed. The NIKA2 data will also be combined with newly obtained radio continuum observations from the GMRT.
obtained with the Herschel Space Observatory. The data obtained is being
used to study the far-infrared spectral energy distribution of nearby galaxies to
learn more about the physical properties of cosmic dust and the ways in which
galaxies have evolved and changed with time. Having taken the leading role
in one of Herschel's primary instruments the Cardiff instrumentation group are
now leading the development of instruments for ground based telescopes.
One such instrument, the NIKA2 camera, will be deployed on the IRAM
telescope in autumn 2015. Our proposed project concerns the exploitation of
the unique imaging capabilities of this camera , which is designed to observe
at a wavelength of 1 and 2 mm. The project is to specifically use this data
along with our Herschel data to try and understand physical processes in the
inter-stellar medium not previously observed. The NIKA2 data will also be combined with newly obtained radio continuum observations from the GMRT.
Organisations
People |
ORCID iD |
| Jonathan Davies (Primary Supervisor) | |
| Ruth Evans (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| ST/N504002/1 | 01/10/2015 | 31/03/2021 | |||
| 1644993 | Studentship | ST/N504002/1 | 01/10/2015 | 31/03/2019 | Ruth Evans |
| Description | One of the key issues in galactic dust is measuring the quantity of it. Dust is notoriously difficult to detect in its entirety, This thesis presents the results of a multi-wavelength study into the 3D distribution of dust in the haloes of galaxies. A sample of 31 nearby, edge-on galaxies from the DustPedia database is used to measure the vertical extent of dust above the central plane of galaxy disks at the Herschel PACS 100 & 160 µm and SPIRE 250, 350 & 500 µm bands. I generate a 3D model of the dust to match each galaxy based on the exponential TRIPLEX function, which ensures that line-of-sight effects of inclination can be accounted for when measuring the vertical scaleheight. The galaxy maps and models are stacked at each wavelength to increase the sensitivity of the observations over that of a single map. I carry out the same procedure on WISE 3.4 µm data which traces the oldest, and most extended, stellar population for comparison of the dust scaleheight versus stellar scaleheight. I find that the dust is more vertically extended than the stellar disk by at least a factor of 2 at each wavelength. I fit one-component SEDs to the stacked maps, and find a total dust mass for the sample of 5.97 ±0.65 x10^9 solar masses, an order of magnitude greater than previous estimates. The mass of dust contained at scaleheights greater than the stellar disk is 4.10 ±0.3 x10^8 solar masses, hence 16% of the dust mass is found above the stellar disk. At 350 and 500 µm, the data is not well estimated by a one component modified blackbody spectrum (assuming beta = 1.7), and the emission at these wavelengths is in excess of the estimated values. These results indicate the presence of a large cold dust reservoir that has been previously unaccounted for in the literature. The dust temperature at increasing distance from the plane is found to be relatively constant, in line with radiative transfer models. I also utilise the first high-resolution 1.2 and 2 mm NIKA2 observations of NGC 891 and M99 as science verification for the IMEGIN Large Programme. A two-component blackbody spectrum is fitted to the data and dust temperatures and masses estimated. I find a cold to warm dust ratio of 42.6 and 41.3 for the galaxies respectively, and total dust masses of 8.5 ±0.4 x10^8 solar masses and 1.0 ±0.6 x10^8 solar masses. The temperatures of the cold and warm components are found to be 20.9 and 34.9 K for NGC 891, and 21.2 and 37.7 K for M99. These values are consistent with the literature, and we do not find evidence of a hidden cold dust component at the NIKA2 wavelengths. |
| Exploitation Route | I think that in the future the subject would benefit from radiative transfer modelling of all galaxies in the sample of 33 edge-on galaxies. The results of this project may provide an answer to the dust-energy balance problems that has been so-far unexplained. The NIKA2 Nearby Galaxies large programme will also benefit from further observations and development of the data reduction pipeline. |
| Sectors | Other |