As the second step in our investigation of the mass-to-light ratio of spiral disks, we present the results of a spectroscopic survey of planetary nebulae (PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly Telescope's Medium Resolution Spectrograph, we determine the radial velocities of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15km/s. Although the main purpose of this data set is to facilitate dynamical mass measurements throughout the inner and outer disks of large spiral galaxies, our spectroscopy has other uses as well. Here, we co-add these spectra to show that, to first order, the [OIII] and Balmer line ratios of PNe vary little over the top ~1.5mag of the PN luminosity function.
We report the results of [O III] {lambda}5007 surveys for planetary nebulae (PNe) in six galaxies: NGC 2403, NGC 3115, NGC 3351, NGC 3627, NGC 4258, and NGC 5866. Using on-band/off-band [O III] {lambda}5007 images, as well as images taken in H{alpha}, we identify samples of PNe in these galaxies and derive their distances using the planetary nebula luminosity function (PNLF).
Using a slitless spectroscopy method with the 8.2m Subaru telescope and its FOCAS Cassegrain spectrograph, we have increased the number of planetary nebula (PN) detections and PN velocity measurements in the flattened elliptical galaxy NGC 821. A comparison with the detections reported previously by the Planetary Nebulae Spectrograph group indicates that we have confirmed most of their detections. The velocities measured by the two groups, using different telescopes, spectrographs, and slitless techniques, are in good agreement. We have built a combined sample of 167 PNs and have confirmed the Keplerian decline of the line-of-sight velocity dispersion reported previously. We also confirm misaligned rotation from the combined sample. A dark matter halo may exist around this galaxy, but it is not needed to keep the PN velocities below the local escape velocity as calculated from the visible mass. We have measured the m(5007) magnitudes of 145 PNs and produced a statistically complete sample of 40 PNs in NGC 821. The resulting PN luminosity function (PNLF) was used to estimate a distance modulus of 31.4mag, equivalent to 19Mpc.
Using a slitless spectroscopy method with (1) the 8.2m Subaru telescope and its FOCAS Cassegrain spectrograph and (2) the ESO Very Large Telescope unit 1 (Antu) and its FORS2 Cassegrain spectrograph, we have detected 326 planetary nebulae (PNs) in the giant Virgo elliptical galaxy NGC 4649 (M60) and measured their radial velocities. After rejecting some PNs more likely to belong to the companion galaxy NGC 4647, we have built a catalog with kinematic information for 298 PNs in M60. Using these radial velocities, we have concluded that they support the presence of a dark matter halo around M60. Based on an isotropic, two-component Hernquist model, we estimate the dark matter halo mass within 3R_e_ to be 4x10^11^M_{sun}_, which is almost one-half of the total mass of about 10^12^M_{sun}_ within 3R_e_. This total mass is similar to that estimated from globular cluster, XMM-Newton, and Chandra observations. The dark matter becomes dominant outside. More detailed dynamical modeling of the PN data is being published in a companion paper. We have also measured the m(5007) magnitudes of many of these PNs and built a statistically complete sample of 218 PNs. The resulting PN luminosity function (PNLF) was used to estimate a distance modulus of 30.7+/-0.2mag, equivalent to 14+/-1Mpc. This confirms an earlier PNLF distance measurement based on a much smaller sample. The PNLF distance modulus remains smaller than the surface brightness fluctuation distance modulus by 0.4mag.
For the purposes of identifying microlensing events, the POINT-AGAPE collaboration has been monitoring the Andromeda galaxy (M31) for three seasons (1999-2001) with the Wide Field Camera on the Isaac Newton Telescope. In each season, data are taken for one hour per night for roughly 60 nights during the six months that M31 is visible. The two 33x33arcmin^2^ fields of view straddle the central bulge, northwards and southwards. We have calculated the locations, periods and brightness of 35 414 variable stars in M31 as a by-product of the microlensing search. The variables are classified according to their period and brightness. Rough correspondences with classical types of variable star (such as Population I and II Cepheids, Miras and semiregular long-period variables) are established. The spatial distribution of Population I Cepheids is clearly associated with the spiral arms, while the central concentration of the Miras and long-period variables varies noticeably, the brighter and the shorter period Miras being much more centrally concentrated.
Point & compact H{alpha} sources in the inner of M33
Short Name:
J/AJ/154/268
Date:
21 Oct 2021
Publisher:
CDS
Description:
A variety of interesting objects such as Wolf-Rayet stars, tight OB associations, planetary nebulae, X-ray binaries, etc., can be discovered as point or compact sources in H{alpha} surveys. How these objects distribute through a galaxy sheds light on the galaxy star formation rate and history, mass distribution, and dynamics. The nearby galaxy M33 is an excellent place to study the distribution of H{alpha}-bright point sources in a flocculant spiral galaxy. We have reprocessed an archived WIYN continuum-subtracted H{alpha} image of the inner 6.5'x6.5' of M33 and, employing both eye and machine searches, have tabulated sources with a flux greater than approximately 10^-15^ erg/cm^2^/s. We have effectively recovered previously mapped H II regions and have identified 152 unresolved point sources and 122 marginally resolved compact sources, of which 39 have not been previously identified in any archive. An additional 99 H{alpha} sources were found to have sufficient archival flux values to generate a Spectral Energy Distribution. Using the SED, flux values, H{alpha} flux value, and compactness, we classified 67 of these sources.
We present polarization data for 180 extragalactic sources extracted from the Australia Telescope 20GHz (AT20G) survey catalogue and observed with the Australia Telescope Compact Array during a dedicated, high sensitivity run ({sigma}_P_~1mJy). For the sake of completeness, we extracted the polarization information for seven extended sources from the 9yr Wilkinson Microwave Anisotropy Probe co-added maps at 23GHz. The full sample of 187 sources constitutes a =~99% complete sample of extragalactic sources brighter than S_20GHz_=500mJy at the selection epoch with declination {delta}<-30{deg}. The sample has a 91.4% detection rate in polarization at ~20GHz (94 percent if considering the subsample of point-like sources). We have measurements also at 4.8 and 8.6GHz within ~1 month of the 20GHz observations for 172 sources to reconstruct the spectral properties of the sample in total intensity and in polarization: 143 of them have a polarization detection at all three frequencies. We find that there is no statistically significant evidence of a relationship either between the fraction of polarization and frequency or between the fraction of polarization and the total intensity flux density. This indicates that Faraday depolarization is not very important above 4.8GHz and that the magnetic field is not substantially more ordered in the regions dominating the emission at higher frequencies (up to 20GHz). We estimate the distribution of the polarization fraction and the polarized flux density source counts at ~20GHz.
The catalog contains 510 extragalactic radio sources, and covers all polarization measurements from 1965 to the middle of 1974 and a few other radio and optical data for these sources. The typical observation error was in the range of 1-2 percent in 1965 and 0.5-1 percent in 1974. The selection criterion for sources was that polarization data should be available at least at three wavelengths for each source. This reduced the sample to 510 sources. The catalog includes observational data: classifications, Cambridge numbers, coordinates, degrees of polarization at various wavelengths, polarization angles at each wavelength, largest angular diameters, position angles, and redshifts. The catalog also includes derived data: rotation measures, linear source diameters, polarization angles at wavelength 0 cm, differences between position angle and polarization angle at 0 cm, spectral indices between each pair of successive wavelengths observed, and polarization indices between each pair of successive wavelengths observed.
The Dominion Radio Astrophysical Observatory Deep Field polarization study has been matched with the Spitzer Wide-Area Infrared Extragalactic Survey of the European Large Area Infrared Space Observatory Survey North 1 field. We have used Very Large Array observations with a total intensity rms of 87uJy/beam to match SWIRE counterparts to the radio sources. Infrared color analysis of our radio sample shows that the majority of polarized sources are elliptical galaxies with an embedded active galactic nucleus. Using available redshift catalogs, we found 429 radio sources of which 69 are polarized with redshifts in the range of 0.04<z<3.2. We find no correlation between redshift and percentage polarization for our sample. However, for polarized radio sources, we find a weak correlation between increasing percentage polarization and decreasing luminosity.
We study the resolved stellar populations and derive the star formation history of the Sculptor dwarf irregular galaxy (SDIG), a gas-rich dwarf galaxy member of the NGC 7793 subgroup in the Sculptor group of galaxies. We constructed a colour - magnitude diagram (CMD) using archival observations from the Hubble Space Telescope/Advanced Camera for Surveys in order to examine the stellar content of SDIG, as well as the spatial distribution of stars selected within different stellar evolutionary phases. We derived the star formation history of SDIG using a maximum-likelihood fit to the CMD.
