On the mass-luminosity relation for spiral galaxies.
Spiral and irregular galaxies total mass to neutral hydrogen mass ratio derived from mass- luminosity relations
SPIRAL GALAXY↗
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Dust-to-gas ratio in the outer regions of spiral galaxies
Some spiral galaxies are surrounded by extended clouds of neutral hydrogen; if dust is associated with this gas, the dust should appear as a faint extended reflection nebula illuminated by the light from the entire galaxy. It is suggested that observations of the surface brightness of the outer regions of M83 and M101 could be worthwhile, since these two galaxies are bright and have extended surrounding gas clouds. Such studies would be of interest with regard to the possible presence of faint extended halos of stars around galaxies, the extent of the metallicity gradients in galaxies, and the value of the dust-to-gas ratio in quasar absorption-line systems.
Jura, M.↗
Stellar content of nearby galaxies. III - The local group spiral galaxy M33
BVRI CCD photometry is presented for stars brighter than V = 21 mag in four fields in the nearby spiral galaxy M33. V vs (B - V) and I vs (V - I) color-magnitude diagrams clearly show both a young stellar population (as indicated by the blue main sequence and red supergiant plumes) as well as an intermediate-age population of asymptotic giant branch stars. Deep photometry in the outer field (where crowding is less severe) reveals a population consistent in color and magnitude with the tip of the first red giant branch. The M33 distance modulus, 24.6 + or - 0.3 mag, derived from this Population II component is consistent with a recent redetermination of the distance modulus found from Population I Cepheid variables. Finally, some evidence is presented for a radial gradient in the average internal reddening for the fields in M33 reported here.
Wilson, Christine D.↗
The IRAS galaxy 0421 + 040P06 - An active spiral (?) galaxy with extended radio lobes
The infrared bright galaxy 0421 + 040P06 detected by IRAS at 25 and 60 microns was studied at optical, infrared, and radio wavelength. It is a luminous galaxy with apparent spiral structure emitting 4 x 10 to the 37th power from far-infrared to optical wavelengths. Optical spectroscopy reveals a Seyfert 2 emission line spectrum, making 0421 + 040P06 the first active galaxy selected from an unbiased infrared survey of galaxies. The fact that this galaxy shows a flatter energy distribution with more 25 micron emission than other galaxies in the infrared sample may be related to the presence of an intense active nucleus. The radio observations reveal the presence of a non-thermal source that, at 6 cm, shows a prominent double lobed structure 20 to 30 kpc in size extending beyond the optical confines of the galaxy. The radio source is three to ten times larger than structures previously seen in spiral galaxies.
Beichman, C.↗
Star formation in grand design and flocculent spiral galaxies
An examination is conducted of the colors and neutral hydrogen contents of spiral galaxies which have been classified in the Elmegreen and Elmegreen arm morphology system. Using these data, possible differences between the star formation activity in spiral galaxies with and without classic spiral arms are delineated. At the same revised Hubble type, spiral galaxies with regular global arm patterns (the grand design spirals) are bluer than spiral galaxies lacking such patterns (the flocculent spirals) by a small, but statistically significant amount (approximately 0.05 in B-V and approximately 0.15 in U-V). The neutral hydrogen contents of the two groups are roughly similar, implying the star formation rate averaged over a Hubble time has been approximately the same in grand design and flocculent systems. The color differences can be explained either by using an initial mass function in the flocculent spiral galaxies which is deficient in massive stars by a factor of 2 compared with the grand design systems, or by a decrease of 30 percent in the ratio of recent to past star formation rates in flocculent galaxies. The possibility is discussed that systematic Hubble type misclassifications significantly affect these conclusions.
Romanishin, W.↗
The IRAS galaxy 0421+040P06: An active spiral (?) galaxy with extended radio lobes
The infrared bright galaxy 0421+040P06 detected by IRAS at 25 and 60 microns was studied at optical, infrared, and radio wavelength. It is a luminous galaxy with apparent spiral structure emitting 4 x 10 to the 37th power from far-infrared to optical wavelengths. Optical spectroscopy reveals a Seyfert 2 emission line spectrum, making 0421+040P06 the first active galaxy selected from an unbiased infrared survey of galaxies. The fact that this galaxy shows a flatter energy distribution with more 25 micron emission than other galaxies in the infrared sample may be related to the presence of an intense active nucleus. The radio observations reveal the presence of a non-thermal source that, at 6 cm, shows a prominent double lobed structure 20 to 30 kpc in size extending beyond the optical confines of the galaxy. The radio source is three to ten times larger than structures previously seen in spiral galaxies.
Beichman, C. A.↗
Three New Spiral Galaxies with Active Nuclei Producing Double Radio Lobes
Abstract Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies. However, several double-lobed radio sources have been solidly found to be associated with spiral galaxies. By cross-matching ∼9 × 10 5 spiral galaxies selected from the Sloan Digital Sky Survey DR8 data with the full 1.4 GHz radio source catalogs of NRAO VLA Sky Survey and Faint Images of the Radio Sky at Twenty-centimeters, we identify three new spiral galaxies: J0326−0623, J1110+0321 and J1134+3046 that produce double radio lobes, and five double-lobed spirals previously known. By combining the newly discovered and all the other known cases in literature, we confirm the relation that more massive spiral galaxies could produce more powerful radio lobes. We find that most of these spiral galaxies are located in a galaxy group or a poor cluster, in which the environment is denser than in the field, and about half of them are the central brightest galaxies in their parent system. We therefore suggest that the environment is one of the key factors for a spiral to produce double radio lobes.
Astronomy & Astrophysics↗
The gas/dust ratio in spiral galaxies
IRAS data are used here to calculate warm dust masses, which are then compared with the molecular and atomic gas masses for 58 spiral galaxies in order to constrain the fraction and the phase of the interstellar medium in spiral galaxies that contributes to the emission measured by IRAS. The dispersion in the ratio of dust mass to total gas mass is larger than expected on the basis of measurement errors. The dispersion in the ratio of dust mass to inner disk gas mass is less than the dispersion in the ratio of IR to radio emission. The inner gas to warm dust mass ratio for spiral galaxies is 1080 + or - 70, indicating that 80-90 percent of the dust mass in spiral galaxies is radiating at over 100 microns and has a temperature less than about 30 K. However, the bulk of the dust in spiral galaxies is less than about 15 K regardless of the phase of the ISM. Both H I and H2-associated dust contributes to the warm 30 K emission.
Devereux, Nicholas A.↗
Infrared emission and tidal interactions of spiral galaxies
Computer simulations of tidal interactions of spiral galaxies are used to attempt to understand recent discoveries about infrared (IR) emitting galaxies. It is found that the stronger tidal perturbation by a companion the more disk gas clouds are thrown into nucleus crossing orbits and the greater the velocity jumps crossing spiral arms. Both these tidally created characteristics would create more IR emission by high speed cloud collisions and more IR via effects of recently formed stars. This expectation at greater tidal perturbation matches the observation of greater IR emission for spiral galaxies with closer and/or more massive companions. The greater collision velocities found at stronger perturbations on the models will also result in higher dust temperature in the colliding clouds. In the IR pairs examined, most have only one member, the larger, detected and when both are detected, the larger is always the more luminous. In simulations and in a simple analytic description of the strong distance dependence of the tidal force, it is found that the big galaxy of a pair is more strongly affected than the small.
Byrd, Gene G.↗
High chemical abundances in stripped Virgo spiral galaxies
Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).
Skillman, E. D.↗
Galaxy interactions and star formation: Results of a survey of global H-alpha emission in spiral galaxies in 8 clusters
Kennicutt and Kent (1983) have shown that the global H alpha emission from a spiral galaxy is an indicator of the formation rate of massive stars. Moss, Whittle and Irwin (1988) have surveyed two clusters (Abell 347 and 1367) for galaxies with H alpha emission using a high dispersion objective prism technique. The purpose of the survey is to investigate environmental effects on star formation in spiral galaxies, and in particular to ascertain whether star formation is enhanced in cluster spirals. Approximately 20 percent of CGCG galaxies were detected in emission. Two plates of excellent quality were obtained for each of the two clusters, and galaxies were only identified to have emission if this was detected on both plates of a plate pair. In this way, plate flaws and other spurious identifications of emission could be rejected, and weak emission confirmed. The results of this survey have been discussed by Moss (1987). The detected galaxies are of types SO-a and later. The frequency with which galaxies are detected in emission increases towards later morphological type as expected (cf. Kennicutt and Kent 1983). There is no evidence of any dependence of the frequency of detected emission on the absolute magnitude of the galaxy (cf. Moss and Whittle 1990), but there is a strong correlation between a disturbed morphological appearance of the galaxy and the detection of emission. Furthermore it is found that the emission is more centrally concentrated in those galaxies which show a disturbed morphology. It may be noted that the objective prism plate gives a spectrum of a 400 A region around rest wavelength H alpha, but superposed on this is the H alpha emission from the galaxy which, because the light is essentially monochromatic, results in a true two-dimensional image of the H alpha distribution. The visual appearance of the emission on the prism plates was classified according to its diffuseness on a 5 point scale (very diffuse, diffuse, intermediate, compact, and very compact). In tabular form, the relation is shown between this classification and a morphologically disturbed appearance for the galaxy.
Moss, C.↗
The Spatial Variation of the Infrared-to-Radio Ratio in Spiral Galaxies
We have produced two-dimensional maps of the intensity ratio, Q60, of 60 µm infrared to 20 cm radio continuum emission, for a set of 25 nearby galaxies, mostly spirals.
galaxies↗
Polarimetric observations of spiral galaxies.
Photoelectric polarimetric observations of spiral galaxies, noting interstellar dust contribution to polarized light
Appenzeller, I.↗
H II regions and the abundance properties of spiral galaxies
We investigate the relationships between the characteristic oxygen abundance, the radial abundance gradient, and the macroscopic properties of spiral galaxies by examining the properties of individual H II regions within those galaxies. Our observations of the line flux ratio (O II) lambda lambda 3726, 3729 + (O III) lambda lambda 4959, 5007)/H beta for 159 H II regions in 14 spiral galaxies are combined with published data to provide a sample of 39 disk galaxies for which (O II) + (O III)/H beta has been measured for at least five H II regions. We find that the characteristic gas-phase abundances and luminosities of spiral galaxies are strongly correlated. This relationship maps almost directly onto the luminosity-metallicity relationship of irregular galaxies and is also quite similar to that found for elliptical and dwarf spheroidal galaxies. Within our sample of spirals, a strong correlation between characteristic abundance and Hubble type also exists. The correlation between luminosity and Hubble type complicates the issue, but we discuss several interpretations of the correlations. The relationship between circular velocity and characteristic abundance is also discussed. We find that the slopes of the radial abundance gradients, when expressed in units of dex/isophotal radius, do not significantly correlate with either luminosity or Hubble type. However, the hypothesis that both early and very late type spirals have shallower gradients than intermediate spirals is consistent with the data. We find suggestive evidence that the presence of a bar induces a flatter gradient and also briefly discuss whether abundance gradients are exponential, as is usually assumed. We investigate the properties of individual H II regions in a subset of 42 regions for which we have spectra that cover almost the entire spectral range from 3500 to 9800 A. We use those data to estimate the densitites and ionizing spectra within the H II regions. We confirm that the ionizing spectrum hardens with increasing radius and decreasing abundance. We find no correlation between the ionization parameter and either radius or abundance, but this may be due to significant scatter introduced by the simple conversion of line ratios to ionization parameter.
Zaritsky, Dennis↗
Detection of a Superluminous Spiral Galaxy in the Heart of a Massive Galaxy Cluster
It is well established that brightest cluster galaxies (BCGs), residing in the centers of galaxy clusters, are typically massive and quenched galaxies with cD or elliptical morphology. An optical survey suggested that an exotic galaxy population, superluminous spiral and lenticular galaxies, could be the BCGs of some galaxy clusters. Because the cluster membership and the centroid of a cluster cannot be accurately determined based solely on optical data, we followed up a sample of superluminous disk galaxies and their environments using XMM-Newton X-ray observations. Specifically, we explored seven superluminous spiral and lenticular galaxies that are candidate BCGs. We detected massive galaxy clusters around five superluminous disk galaxies and established that one superluminous spiral, 2MASX J16273931+3002239, is the central BCG of a galaxy cluster. The temperature and total mass of the cluster are ${{kT}}_{500}={3.55}_{-0.20}^{+0.18}$ keV and M 500 = (2.39 ± 0.19) × 10 14 M ⊙ . We identified the central galaxies of the four clusters that do not host superluminous disk galaxies at their cores, and established that the centrals are massive elliptical galaxies. However, for two of the clusters, the offset superluminous spirals are brighter than the central galaxies, implying that the superluminous disk galaxies are the brightest cluster galaxies. Our results demonstrate that superluminous disk galaxies are rarely the central systems of galaxy clusters. This is likely because galactic disks are destroyed by major mergers, which are more frequent in high-density environments. We speculate that the disks of superluminous disk galaxies in cluster cores may have been reformed due to mergers with gas-rich satellites.
79 ASTRONOMY AND ASTROPHYSICS↗
On the angular-momentum distribution in the disks of spiral galaxies.
Angular momentum distribution in disks of spiral galaxies based on rotation-curves and mass distribution
ANGULAR MOMENTUM↗
SDSS-IV MaNGA: the chemical co-evolution of gas and stars in spiral galaxies
ABSTRACT We investigate archaeologically how the metallicity in both stellar and gaseous components of spiral galaxies of differing masses evolve with time, using data from the SDSS-IV MaNGA survey. For the stellar component, we can measure this evolution directly by decomposing the galaxy absorption-line spectra into populations of different ages and determining their metallicities. For the gaseous component, we can only measure the present-day metallicity directly from emission lines. However, there is a well-established relationship between gas metallicity, stellar mass, and star formation rate which does not evolve significantly with redshift; since the latter two quantities can be determined directly for any epoch from the decomposition of the absorption-line spectra, we can use this relationship to infer the variation in gas metallicity over cosmic time. Comparison of present-day values derived in this way with those obtained directly from the emission lines confirms the validity of the method. Application of this approach to a sample of 1619 spiral galaxies reveals how the metallicity of these systems has changed over the last 10 billion yr since cosmic noon. For lower-mass galaxies, both stellar and gaseous metallicity increase together, as one might expect in well-mixed fairly isolated systems. In higher-mass systems, the average stellar metallicity has not increased in step with the inferred gas metallicity, and actually decreases with time. Such disjoint behaviour is what one might expect if these more massive systems have accreted significant amounts of largely pristine gas over their lifetimes, and this material has not been well mixed into the galaxies.
79 ASTRONOMY AND ASTROPHYSICS↗
The spatial variation of the infrared-to-radio ratio in spiral galaxies
We have produced two-dimensional maps of the intensity ratio, Q(sub 60), of 60 micron infrared to 20 cm radio continuum emission, for a set of 25 nearby galaxies, mostly spirals. The ratio maps were obtained from infrared images made using IRAS data with the maximum correlation method, and radio images made using VLA data. Before taking the ratio, the radio images were processed so as to have the same resolution properties as the infrared images; the final spatial resolution in all cases is approximately 1 min, corresponding to 1 - 2 kpc for most galaxies. This resolution represents a significant improvement over previous studies. Our new high-resolution maps confirm the slow decrease of Q(sub 60) with increasing radial distance from the nucleus, but show additional structure which is probably associated with separate sites of active star formation in the spiral arms. The maps show Q(sub 60) to be more closely related to infrared surface brightness than to the radial distance r in the galaxy disk. We note also that the Q(sub 60) gradients are absent (or at least reduced) for the edge-on galaxies, a property which can be attributed to the dilution of contrast due to the averaging of the additional structure along the line of sight. The results are all in qualitative agreement with the suggestion that the radio image represents a smeared version of the infrared image, as would be expected on the basis of current models in which the infrared-radio correlation is driven by the formation of massive stars, and the intensity distribution of radio emission is smeared as a result of the propagation of energetic electrons accelerated during the supernova phase.
Marsh, K. A.↗