Raven Eyes Elliptical Galaxies and Star Clusters T. J. Davidge November 24, 2015
Why Maffei1 and the Glimpse Clusters? Targets were selected at low Galactic latitudes to maximize chances of finding a suitable guide star asterism (even then had some issues). Maffei1 is the nearest(?) elliptical galaxy, and has been understudied because of very high line of sight extinction. What is the age distribution of stars in Maffei1? Is there evidence for a recent merger of starforming activity? Evidence for recent activity might be found in the nucleus, and an examination of this region requires good image quality. Clusters at low Galactic latitudes are of fundamental interest for probing the early evolution of the Galaxy. Glimpse 01 and 02 are recently discovered clusters, that are highly obscured. Because they are at low Galactic latitudes there is considerable foreground star contamination. By working at high angular resolution it is possible to resolve stars near the cluster centers, where the ratio of cluster to foreground stars is maximized. Glimpse 01 is a massive (~10 5 solar) cluster has an age of 400 800 Myr, and so should contain a large AGB component (hence is ideal for NIR and MIR studies of the SED). What are the fundamental parameters of the clusters ([M/H], distance, M K, etc)?
Comparing the Maffei1 Raven Light Profile with HST Data 1800 sec total exposure time with the H+K grism. K spectrum was too noisy, so worked on the H-band. Even though Maffei1 is an extended object, a sense of the image quality can be made by making comparisons with published light profiles. Obtain reasonable agreement with F814W profile obtained by Buta& McCall (2003).
The Detection of C Stars in Maffei1 Extracted spectra of the nucleus and circumnuclear regions. The absorption spectrum is dominated by blends of moelcular (CO) and atomic transitions. Detect an absorption trough longwardof 1.76 µm that is not present in the spectra of O-rich K,M giants The trough matches a feature in C star spectra that is due to C 2. The feature is more pronounced in the circumnuclear spectrum.
Modelling the C Star Contribution Constructed solar metallicitymodel spectra for SSPs using Rayner et al. (2009) stellar library. The baseline models did not include C stars, and did not match the absorption trough longwardof 1.76µm. A 10 20% contribution from stars of type C5 can reproduce the depth of the C 2 feature. The near-infrared colors of Maffei1 are also indicative of a large population with an age similar to that expected to produce C stars. Maffei1 is probably an E+A galaxy.
Glimpse C01 (NIR) JHK observations were recorded with 0.052 arcsec sampling. Shallow and deep exposures were recorded in each filter. FWHM ~ 0.22 arcsecin composite H-band 2 second exposure (combined six 2 sec exposures).
FWHM Stability A large number of exposures were recorded as part of the set-up, allowing image quality to be charted as a function of time. Note ~0.2 arcsec FWHM floor.
Glimpse C01 (MIR) Glimpse C01 has an age where massive AGB stars should be present, and may show signs of circumstellar emission. Data were recorded with 0.02 arcsecpixel sampling. IRCS has three narrow-band filters that sample wavelengths longward of 3µm. H 2 O: 3.05µm PAH: 3.30µm H3+: 3.41µm 80 100 seconds per filter. Note Airey pattern.
Glimpse C01 Anisoplanicity 0.120 0.108 λ/d = 0.079 arcsec 0.110 0.096 0.112
Glimpse C01 + C02: What is to come. Extend assessment of image quality and its variation. Photometric measurements: (K, J-K) CMD and (J-H, J-K) two color diagram. Examination of spectral energy distributions of the brightest stars by combining NIR and MIR measurements. Conduct a detailed comparison with archival Spitzer [3.5] images Working at or near the diffraction limit of large ground-based telescopes is a scientific niche that AO systems (including Raven s successor) should exploit. Spitzer [3.5] image of Glimpse C01: FWHM ~ 1.1 arcsec
THANKS To the people who built and operated Raven. For the opportunity to participate as a science team member.