Photometry is tabulated for 1189 galaxies in 19 OSIS-V (CFHT) images in the direction of the galaxy cluster Abell 2390. The images cover 270 sq. deg., and extend out to the virial radius of the cluster. Three narrow filters are used to determine the flux above the continuum between wavelengths 7897 and 8245 {AA}, corresponding to H-alpha at 0.2033<z<0.2563. The absolute flux values are uncertain by about 30% due to zero point uncertainty; we also tabulate the equivalent width which is independent of this zero point. Only strong emission line cluster members (equivalent width greater than about 50{AA}) are detectable, by design. Galaxies with spectra available from the CNOC survey (Abraham=1996ApJ...471..694A) are identified.
Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using the High Resolution Spectrograph on the Hobby-Eberly Telescope. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the H{alpha} feature. We have identified periodic signals for six stars, with periods ranging from days to more than 10 years, and find long-term trends for seven others. Stellar cycles with P>=1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate H{alpha} variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, H{alpha} variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f in that system. In general, though, we find that H{alpha} is not frequently correlated with RV at the precision (typically 6-7m/s) of our measurements.
In this paper we study long slit spectra in the region of H{alpha} emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected H II regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/H{alpha} ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/H{alpha} ratios measured for disk H II regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of H{alpha} equivalent width.
We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and Hα filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their Hα emission) in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant Hα emission that probably represent uncatalogued HII regions.
Omicron Aquarii is a late-type, Be shell star with a stable and nearly symmetric H{alpha} emission line. We combine H{alpha} interferometric observations obtained with the Navy Precision Optical Interferometer covering 2007 through 2014 with H{alpha} spectroscopic observations over the same period and a 2008 observation of the system's near-infrared spectral energy distribution to constrain the properties of o Aqr's circumstellar disk. All observations are consistent with a circumstellar disk seen at an inclination of 75{deg}+/-3{deg} with a position angle on the sky of 110{deg}+/-8{deg} measured East from North. From the best-fit disk density model, we find that 90% of the H{alpha} emission arises from within 9.5 stellar radii, and the mass associated with this H{alpha} disk is ~1.8x10^-10^ of the stellar mass, and that the associated angular momentum, assuming Keplerian rotation for the disk, is ~1.6x10^-8^ of the total stellar angular momentum. The occurrence of a central quasi-emission feature in Mg II {lambda}4481 is also predicted by this best-fit disk model and the computed profile compares successfully with observations from 1999. To obtain consistency between the H{alpha} line profile modeling and the other constraints, it was necessary in the profile fitting to weight the line core (emission peaks and central depression) more heavily than the line wings, which were not well reproduced by our models. This may reflect the limitation of assuming a single power law for the disk's variation in equatorial density. The best-fit disk density model for o Aqr predicts that H{alpha} is near its maximum strength as a function of disk density, and hence the H{alpha} equivalent width and line profile change only weakly in response to large (factor of ~5) changes in the disk density. This may in part explain the remarkable observed stability of o Aqr's H{alpha} emission line profile.
H{alpha} interferometry obs. of the Be star 48 Per
Short Name:
J/ApJ/843/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We utilize a multi-step modeling process to produce synthetic interferometric and spectroscopic observables, which are then compared to their observed counterparts. Our extensive set of interferometric observations of the Be star 48 Per, totaling 291 data points, were obtained at the Navy Precision Optical Interferometer from 2006 November 07 to 23. Our models were further constrained by comparison with contemporaneous H{alpha} line spectroscopy obtained at the John S. Hall Telescope at the Lowell Observatory on 2006 November 1. Theoretical spectral energy distributions, SEDs, for 48 Per were confirmed by comparison with observations over a wavelength regime of 0.4-60 {mu}m from Touhami+ (2010PASP..122..379T) and Vieira+ (2017MNRAS.464.3071V). Our best-fitting combined model from H{alpha} spectroscopy, H{alpha} interferometry, and SED fitting has a power-law density fall off, n, of 2.3 and an initial density at the stellar surface of {rho}_0_=1.0x10^-11^g/cm^-3^ with an inclination constrained by H{alpha} spectroscopy and interferometry of 45+/-5{deg}. The position angle for the system, measured east from north, is 114+/-18{deg}. Our best-fit model shows that the disk emission originates in a moderately large disk with a radius of 25 R*, which is consistent with a disk mass of approximately 5x10^24^g or 3x10^-10^M*. Finally, we compare our results with previous studies of 48 Per by Quirrenbach+ (1997ApJ...479..477Q) and find agreement, whereas our disk size does not agree with Delaa+ (2011A&A...529A..87D), based on a much smaller visibility set.
We have observed three luminous infrared galaxy systems (LIRGS) which are pairs of interacting galaxies, with the Galaxy H{alpha} Fabry-Perot system (GH{alpha}FaS) mounted on the 4.2m William Herschel Telescope at the Roque de los Muchachos Observatory, and combined the observations with the Atacama Large Millimeter Array (ALMA) observations of these systems in CO emission to compare the physical properties of the star formation regions and the molecular gas clouds, and specifically the internal kinematics of the star forming regions. We identified 88 star forming regions in the H$\alpha$ emission data-cubes, and 27 molecular cloud complexes in the CO emission data-cubes. The surface densities of the star formation rate and the molecular gas are significantly higher in these systems than in non-interacting galaxies and the Galaxy, and are closer to the surface densities of the star formation rate and the molecular gas of extreme star forming galaxies at higher redshifts. The large values of the velocity dispersion also show the enhanced gas surface density. The HII regions are situated on the {Sigma}_SFR_-{sigma}_v_ envelope, and so are also in virial equilibrium. Since the virial parameter decreases with the surface densities of both the star formation rate and the molecular gas, we claim that the clouds presented here are gravitationally dominated rather than being in equilibrium with the external pressure.
We investigate the star formation rate and its location in the major merger cluster Abell 2465 at z=0.245. Optical properties of the cluster are described in. Measurements of the H{alpha} and infrared dust emission of galaxies in the cluster were made with an interference filter centred on the redshifted line at a wavelength of 817 nm and utilized data from the Wide-field Infrared Survey Explorer satellite 12{mu}m band. Imaging in the Johnson U and B bands was obtained, and along with Sloan Digital Sky Survey u and r was used to study the blue fraction, which appears enhanced, as a further signature of star formation in the cluster. Star formation rates were calculated using standard calibrations. The total star formation rate normalized by the cluster mass, {Sigma}SFR/M_cl_ compared to compilations for other clusters indicate that the components of Abell 2465 lie above the mean z and M_cl_ relations, suggestive that interacting galaxy clusters have enhanced star formation. The projected radial distribution of the star-forming galaxies does not follow an NFW profile and is relatively flat indicating that fewer star-forming galaxies are in the cluster centre. The morphologies of the H{alpha} sources within R_200_ for the cluster as a whole indicate that many are disturbed or merging, suggesting that a combination of merging or harassment is working.
Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the Southern Hemisphere. Although several studies have been dedicated to define its members, their kinematics, hot and cold gas content, in particular HI, their present star formation activity is yet unknown. For the first time, we map the H{alpha} distribution as a possible indicator of star formation activity of Dorado members a large fraction of which show interaction and merging signatures, regardless of their morphological type. With the 2.5m du Pont and the 1m Swope telescopes we obtained narrow-band, calibrated images of 14 galaxies, forming the backbone of the group, mapping H{alpha}+[NII] down to few 10^-17^erg/cm^2^/s/arcsec^2^. We estimated the galaxy star formation rate from the H{alpha} fluxes, corrected for Galaxy foreground extinction and [NII] contamination. H{alpha}+[NII] emission has been detected in all galaxies. HII regions clearly emerge in late-type galaxies, while in early-type galaxies the H{alpha}+[NII] emission is dominated by [NII], especially in the central regions. However, HII complexes are revealed in four early-type galaxies. Even in the compact group SGC 0414-5559, in the projected centre of Dorado, HII regions are found both through out the late-type galaxies and in the very outskirts of early-type members. Considering the Dorado group as a whole, we notice that the H{alpha}+[NII] equivalent width, a measure of the specific star formation, increases with the morphological type, from early to late-type members, although it remains lower that what observed in similar surveys of spiral galaxies. The star formation rate of the spiral members is in the range of what observed in similar galaxies surveys (James et al., 2004A&A...414...23J, Cat. J/A+A/414/23). However, in three spiral NGC 1536, PGC 75125 and IC 2058 the star formation rate is well below the median for their morphological classes. The star formation rate of some early-type members tends, at odds, to be higher than the average derived from H{alpha}+[NII] surveys of this morphological family. We detected in H{alpha}+[NII] all the early type galaxies observed and half of them show HII regions in well shaped rings as well as in their outskirts. These findings suggest that ETGs in this group are not dead galaxies: their star formation has not shutdown yet. Mechanisms such as gas stripping and gas accretion, through galaxy-galaxy interaction, seem relevant in modifying star formation in this evolutionary phase of Dorado.
In a first of a series of studies of the H{alpha}+[NII] emission from nearby spiral galaxies, we present measurements of H{alpha}+[NII] emission from HII regions in M81. Our method uses large-field CCD images and long-slit spectra and is part of the ongoing Beijing-Arizona-Taipei-Connecticut Sky Survey (the BATC survey). The CCD images are taken with the National Astronomical Observatories of China (NAOC) 0.6/0.9m f/3 Schmidt telescope at the Xinglong Observing Station, using a multicolor filter set. The observations reported here were taken on 30 individual nights over the time period 1995 February 5 to 1997 February 19. Spectra of 10 of the brightest HII regions are obtained using the NAOC 2.16m telescope with a Tek 1024x1024 CCD, between 1997 April 9 and 11. The continua of the spectra are calibrated by flux-calibrated images taken from the Schmidt observations. We determine the continuum component of our H{alpha}+[NII] image via interpolation from the more accurately measured backgrounds (M81 starlight) obtained from the two neighboring (in wavelength) BATC filter images. We use the calibrated fluxes of H{alpha}+[NII] emission from the spectra to normalize this interpolated, continuum-subtracted H{alpha}+[NII] image. We estimate the zero-point uncertainty of the measured H{alpha}+[NII] emission flux to be 8%. A catalog of H{alpha}+[NII] fluxes for 456 HII regions is provided, with those fluxes being on a more consistent linear scale than previously available. The logarithmically binned H{alpha}+[NII] luminosity function of HII regions is found to have slope {alpha}=-0.70, consistent with previous results (which allowed {alpha}=-0.5 to -0.8). From the overall H{alpha}+[NII] luminosity of the HII regions, the star formation rate of M81 is found to be ~0.68M_{sun}_/yr, modulo uncertainty with extinction corrections.