A Photometric Study of "The Antennae Galaxies" Using GSAOI/GeMS" & "J2240-0927: A Case Study of a Quasar Light Echo Using the Gemini-GMOS IFU

Monday, 17 February 2014 9 a.m. — 10 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
MARCUS WONG; REBECCA DAVIES (AGUSS Student, Monash University Clayton, Australia; AGUSS Student, Australian National University, Australia)

A Photometric Study of “The Antennae Galaxies" using GSAOI/GeMS

The twin Gemini telescopes are among the most powerful optical/near-infrared telescope in the world. Since 2012, the Gemini South Adaptive Optics Imager (GSAOI) has been used in conjunction with the Gemini Multi-Conjugate Adaptive Optics System (GeMS), providing diffraction limited images in the 0.9 - 2.4 μm near-infrared wavelength range. We use GSAOI/GeMS to revisit the heavily studied and popular NGC 4038/4039, or more commonly known as 'The Antennae'. The Antennae Galaxies are the youngest and nearest example of a pair of merging spiral galaxies and is well known for its numerous star formation regions. With its superior spatial resolution comparable to Hubble Space Telescope (HST), GSAOI/GeMS is ideally suited to resolve such regions and improve on previous measurements. This study not only aims to confirm previous findings but to also shed new light with high resolution observations made in the Ks filter. I will be presenting the reduction and photometric calibration process of these images. Initial science findings and comparison with published literature results will also be discussed.


J2240-0927: A case study of a quasar light echo using the Gemini-GMOS IFU

The recent discovery of extremely luminous, highly ionized and kinematically disturbed extended narrow line regions around a handful of moderately luminous Seyfert galaxies at intermediate redshift (z = 0.3) has prompted the investigation of possible ionization sources for these objects. The bolometric luminosities of the central AGNs as traced by X-ray and radio observations fall at least two orders of magnitude short of what is required to produce the observed [O III] luminosities; leading to the hypothesis that we are observing light echoes of quasar phases which ceased more recently than the light crossing time of the galaxy. In this talk, I will present Gemini GMOS-IFU data for J2240-0927, a prototypical quasar light echo candidate. Constructing images across different wavelength slices of prominent emission lines such as [O III] indicates that this galaxy has a very complex velocity field, with evidence for at least two emission components over a large percentage of the galaxy. I will discuss the techniques used to extract emission line fluxes, and present maps of characteristic line ratios which allow us to dissect the internal extinction, ionization state, electron temperature and density of each emission component individually. Overall, the kinematics and ionization properties of J2240 suggest that this system is comprised of a galaxy rotating within a large extended narrow-line region; ionized primarily by the central AGN but with a significant contribution from shock excitation in some hot, dense pockets of gas in the outer regions of the galaxy.