19 research outputs found
Planetary Nebulae as Standard Candles. XII. Connecting the Population I and Population II Distance Scales
We report the results of [OIII] lambda 5007 surveys for planetary nebulae
(PNe) in NGC 2403, 3115, 3351, 3627, 4258, and 5866. Using on-band/off-band
[OIII] and H-alpha images, we identify samples of PNe in these galaxies and
derive distances using the planetary nebula luminosity function (PNLF). We then
combine these measurements with previous data to compare the PNLF, Cepheid, and
surface brightness fluctuation (SBF) distance scales. We use a sample of 13
galaxies to show that the absolute magnitude of the PNLF cutoff is fainter in
small, low-metallicity systems, but the trend is well modelled theoretically.
When this dependence is removed, the scatter between the Cepheid and PNLF
distances becomes consistent with the internal errors of the methods and
independent of any obvious galaxy parameter. We then use the data to
recalibrate the zero point of the PNLF distance scale. We use a sample of 28
galaxies to show that the scatter between the PNLF and SBF distance
measurements agrees with that predicted from the techniques' internal errors,
and that no systematic trend exists between the distance residuals and stellar
population. However, we find the PNLF and SBF methods have a significant scale
offset: Cepheid-calibrated PNLF distances are, on average, ~0.3 mag smaller
than Cepheid-calibrated SBF distances. We discuss the possible causes of this
offset, and suggest that internal extinction in the bulges of the SBF
calibration galaxies is the principle cause of the discrepancy. If this is
correct, the SBF-based Hubble Constant must be increased by ~7%. We use our
distance to NGC 4258 to argue that the short distance scale to the LMC is
correct, and that the global Hubble Constant inferred from the HST Key Project
should be increased by 8 +/- 3% to H_0 = 78 +/- 7 km/s/Mpc. (abridged)Comment: 38 pages, 9 figures included, accepted for publication in the
Astrophysical Journa
The Maunakea Spectroscopic Explorer Book 2018
(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is
intended as a concise reference guide to all aspects of the scientific and
technical design of MSE, for the international astronomy and engineering
communities, and related agencies. The current version is a status report of
MSE's science goals and their practical implementation, following the System
Conceptual Design Review, held in January 2018. MSE is a planned 10-m class,
wide-field, optical and near-infrared facility, designed to enable
transformative science, while filling a critical missing gap in the emerging
international network of large-scale astronomical facilities. MSE is completely
dedicated to multi-object spectroscopy of samples of between thousands and
millions of astrophysical objects. It will lead the world in this arena, due to
its unique design capabilities: it will boast a large (11.25 m) aperture and
wide (1.52 sq. degree) field of view; it will have the capabilities to observe
at a wide range of spectral resolutions, from R2500 to R40,000, with massive
multiplexing (4332 spectra per exposure, with all spectral resolutions
available at all times), and an on-target observing efficiency of more than
80%. MSE will unveil the composition and dynamics of the faint Universe and is
designed to excel at precision studies of faint astrophysical phenomena. It
will also provide critical follow-up for multi-wavelength imaging surveys, such
as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field
Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation
Very Large Array.Comment: 5 chapters, 160 pages, 107 figure
The Planetary Nebula System of M33
We report the results of a photometric and spectroscopic survey for planetary
nebulae (PNe) in the Local Group spiral galaxy M33. We use our sample of 152
PNe to derive an [O III] planetary nebula luminosity function (PNLF) distance
of (m-M)_0 = 24.86^+0.07-0.11 (0.94^+0.03-0.05 Mpc). Although this value is ~
15% larger than the galaxy's Cepheid distance, the discrepancy likely arises
from differing assumptions about the system's internal extinction. Our
photometry (which extends >3 mag down the PNLF), also reveals that the
faint-end of M33's PN luminosity function is non-monotonic, with an inflection
point ~2 mag below the PNLF cutoff. We argue that this feature is due to the
galaxy's large population of high core-mass planetaries, and that its amplitude
may eventually be useful as a diagnostic for studies of stellar populations.
Fiber-coupled spectroscopy of 140 of the PN candidates confirms that M33's PN
population rotates along with the old disk, with a small asymmetric drift of \~
10km/s. Remarkably, the population's line-of-sight velocity dispersion varies
little over ~4 optical disk scale lengths, with sigma_{rad}~20km/s. We show
that this is due to a combination of factors, including a decline in the radial
component of the velocity ellipsoid at small galactocentric radii, and a
gradient in the ratio of the vertical to radial velocity dispersion. We use our
data to show that the mass scale length of M33's disk is ~2.3 times larger than
that of the system's IR luminosity and that the disk's V-band mass-to-light
ratio changes from M/L_V ~0.3 in the galaxy's inner regions to M/L_V ~2.0 at ~9
kpc. Models in which the dark matter is distributed in the plane of the galaxy
are excluded by our data. (abridged)Comment: 45 pages, including 12 figures (some with reduced resolution);
accepted for publication in the Astrophysical Journa
Maximum outreach... minimum budget
Many astronomical institutions have budgetary constraints that prevent them from spending large amounts on public outreach. This is especially true for smaller organizations, such as the Canada-France-Hawaii Telescope (CFHT), where manpower and funding are at a premium. To maximize our impact, we employ unconventional and affordable outreach techniques that underscore our commitment to astronomy education and our local community. We participate in many unique community interactions, ranging from rodeo calf-dressing tournaments to art gallery exhibitions of CFHT images. Further, we have developed many creative methods to communicate complex astronomical concepts to both children and adults, including the use of a modified webcam to teach infrared astronomy and the production of online newsletter for parents, children, and educators. This presentation will discuss the outreach methods CFHT
has found most effective in our local schools and our rural community
Recommended from our members
The Maunakea Spectroscopic Explorer Book 2018
(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is
intended as a concise reference guide to all aspects of the scientific and
technical design of MSE, for the international astronomy and engineering
communities, and related agencies. The current version is a status report of
MSE's science goals and their practical implementation, following the System
Conceptual Design Review, held in January 2018. MSE is a planned 10-m class,
wide-field, optical and near-infrared facility, designed to enable
transformative science, while filling a critical missing gap in the emerging
international network of large-scale astronomical facilities. MSE is completely
dedicated to multi-object spectroscopy of samples of between thousands and
millions of astrophysical objects. It will lead the world in this arena, due to
its unique design capabilities: it will boast a large (11.25 m) aperture and
wide (1.52 sq. degree) field of view; it will have the capabilities to observe
at a wide range of spectral resolutions, from R2500 to R40,000, with massive
multiplexing (4332 spectra per exposure, with all spectral resolutions
available at all times), and an on-target observing efficiency of more than
80%. MSE will unveil the composition and dynamics of the faint Universe and is
designed to excel at precision studies of faint astrophysical phenomena. It
will also provide critical follow-up for multi-wavelength imaging surveys, such
as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field
Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation
Very Large Array
The Detailed Science Case for the Maunakea Spectroscopic Explorer: the Composition and Dynamics of the Faint Universe
210 pages, 91 figures. Exposure draft. Appendices to the Detailed Science Case can be found at http://mse.cfht.hawaii.edu/docs/MSE is an 11.25m aperture observatory with a 1.5 square degree field of view that will be fully dedicated to multi-object spectroscopy. More than 3200 fibres will feed spectrographs operating at low (R ~ 2000 - 3500) and moderate (R ~ 6000) spectral resolution, and approximately 1000 fibers will feed spectrographs operating at high (R ~ 40000) resolution. MSE is designed to enable transformational science in areas as diverse as tomographic mapping of the interstellar and intergalactic media; the in-situ chemical tagging of thick disk and halo stars; connecting galaxies to their large scale structure; measuring the mass functions of cold dark matter sub-halos in galaxy and cluster-scale hosts; reverberation mapping of supermassive black holes in quasars; next generation cosmological surveys using redshift space distortions and peculiar velocities. MSE is an essential follow-up facility to current and next generations of multi-wavelength imaging surveys, including LSST, Gaia, Euclid, WFIRST, PLATO, and the SKA, and is designed to complement and go beyond the science goals of other planned and current spectroscopic capabilities like VISTA/4MOST, WHT/WEAVE, AAT/HERMES and Subaru/PFS. It is an ideal feeder facility for E-ELT, TMT and GMT, and provides the missing link between wide field imaging and small field precision astronomy. MSE is optimized for high throughput, high signal-to-noise observations of the faintest sources in the Universe with high quality calibration and stability being ensured through the dedicated operational mode of the observatory. (abridged