arXiv subjects

Beverly J. Smith

Publications and source records attributed to Beverly J. Smith.

At least 19 recordsLinked to original sources

arXiv2026

Dynamics of tidal dwarf galaxies in the system Arp 72

Some interactions between galaxies produce tidal tails primarily composed of material from their disks. Within these tails, concentrations of gas and stars can form, resembling dwarf galaxies. These tidal objects often begin to form stars and become dynamically independent of their parent galaxies, leading to their classification as Tidal Dwarf Galaxies (TDGs). By definition, TDGs should consist solely of baryonic material, with a negligible dark matter fraction. In this study, we analyze the dynamics of two TDGs in the Arp 72 system using high-resolution Hα observations obtained with the MEGARA multi-spectrograph at the GTC (Gran Telescopio Canarias) and neutral hydrogen (HI) data from the GMRT (Giant Metrewave Radio Telescope). The HI data were also used to determine the gas mass. We derived the rotation curves and velocity dispersion from the kinematic data, which allowed us to estimate the dynamical mass of the systems. The TDGs were modeled through 3D fitting as rotating disks with additional pressure support, assuming a mass distribution following an exponential law. The gas mass was combined with the stellar mass to determine the total baryonic mass. Under specific dynamical considerations, we established the relationship between the dynamical mass and the baryonic mass. Additionally, we used the pressure-support corrected circular velocity to compare the behavior of TDGs in the context of the baryonic Tully-Fisher relation (BTFR) with the literature, showing how detached TDGs fall off the relation. The two studied objects are consistent with the expected properties of a TDG.

astro-ph.GA↗

arXiv2026

Galaxy Spiral Arm Count vs. Concentration and Mass: A First Look with Euclid

Using catalogued information from Euclid Quick Data Release 1, we compare 2-armed and 3-armed spiral galaxies as classified by the Euclid Zoobot software. Two-armed galaxies have larger concentrations, lower stellar masses (M*), and lower star formation rates (SFRs) on average than 3-armed galaxies. For a given M*, 2-armed galaxies have larger concentrations than 3-armed galaxies. These trends have been seen before in nearby galaxies; with Euclid we extend the patterns to redshifts z = 0.4 - 1. Two-armed galaxies have lower SFRs because they have lower masses; at fixed M*, 2-armed and 3-armed galaxies have similar SFRs. We see a bend in the concentration-log M* relation for 2-armed galaxies at M* = 10^10.3 M(sun). Above this mass, 2-armed galaxies show significantly larger concentrations than their lower mass counterparts. The observed concentrations of 2-armed galaxies decrease with increasing redshift, perhaps from morphological K-corrections and resolution differences. About 60% - 70% of Euclid spirals are 2-armed, and about 15% - 20% are 3-armed. One-armed galaxies are rare, with low masses compared to 2-armed spirals. We compare these statistics with Galaxy Zoo Sloan Digital Sky Survey arm counts at low z, and tentatively with JWST at higher z. We discuss these results in terms of theoretical models of spiral arm generation and evolution, and compare with statistics of grand design, multi-armed, and flocculent galaxies. There is a need for more quantitative measurements of arm structure beyond arm counts provided by the Zoobot/Galaxy Zoo or the three standard arm classes.

astro-ph.GA↗

arXiv2025

The Complex Multi-Wavelength Morphology of the Peculiar Compact Galaxy Group IC 2431

We present new Chandra X-ray imaging spectroscopy of the compact galaxy group IC 2431, and compare with archival ultraviolet, optical, infrared, and radio images. IC 2431 is a starburst system containing three tidally-distorted disk galaxies. All three galaxies may have active nuclei. One galaxy is classified as an AGN based on its optical spectrum, a second is identified as a possible X-ray AGN based on the Chandra data, and the third galaxy may host a radio AGN. In optical images, a prominent dust lane crosses the southern galaxy, while Spitzer infrared images show a dusty bridge connecting the two brightest galaxies. Chandra maps reveal a massive (2 x 10^7 M(sun)) concentration of hot gas between these two galaxies, as well as several other knots of hot gas and non-thermal emission. The unabsorbed X-ray luminosity of the hot gas in IC 2431 is ~ 1 x 10^42 erg/s, which is enhanced by about a factor of four relative to the star formation rate, compared to other star-forming galaxies. In radio maps, a bright jet/ridge of radio continuum emission extends 4 kpc from one nucleus. We compare the properties of IC 2431 with those of other interacting galaxy systems, and discuss two different scenarios that may account for the peculiarities of IC 2431: ram pressure stripping of the interstellar medium during a head-on collision between two galaxies, or an AGN-powered radio jet that has been distorted by an interaction with interstellar gas during a tidal encounter between galaxies.

astro-ph.GA↗

arXiv2024

Detection and characterization of detached tidal dwarf galaxies

Tidal interactions between galaxies often give rise to tidal tails, which can harbor concentrations of stars and interstellar gas resembling dwarf galaxies. Some of these tidal dwarf galaxies (TDGs) have the potential to detach from their parent galaxies and become independent entities, but their long-term survival is uncertain. In this study, we conducted a search for detached TDGs associated with a sample of 39 interacting galaxy pairs in the local Universe using infrared, ultraviolet, and optical images. We employed IR colors and UV/optical/IR spectral energy distributions to identify potential interlopers, such as foreground stars or background quasars. Through spectroscopic observations using the Boller and Chivens spectrograph at San Pedro Mártir Observatory, we confirmed that six candidate TDGs are at the same redshift as their putative parent galaxy pairs. We identified and measured emission lines in the optical spectra and calculated nebular oxygen abundances, which range from log(O/H) = 8.10 $\pm$ 0.01 to 8.51 $\pm$ 0.02. We have serendipitously discovered an additional detached TDG candidate in Arp72 using available spectra from SDSS. Utilizing the photometric data and the CIGALE code for stellar population and dust emission fitting, we derived the stellar masses, stellar population ages, and stellar metallicities for these detached TDGs. Compared to standard mass-metallicity relations for dwarf galaxies, five of the seven candidates have higher than expected metallicities, confirming their tidal origins. One of the seven candidates remains unclear due to large uncertainties in metallicity, and another has stellar and nebular metallicities compatible with those of a preexisting dwarf galaxy. The latter object is relatively compact in the optical relative to its stellar mass, in contrast to the other candidate TDGs [abridged].

astro-ph.GA↗

arXiv2024

Grand Design vs. Multi-Armed Spiral Galaxies: Dependence on Galaxy Structure

We developed an algorithm to use Galaxy Zoo 3D spiral arm masks produced by citizen scientist volunteers to semi-automatically classify spiral galaxies as either multi-armed or grand design spirals. Our final sample consists of 299 multi-armed and 245 grand design galaxies. On average, the grand design galaxies have smaller stellar masses than the multi-armed galaxies. For a given stellar mass, the grand design galaxies have larger concentrations, earlier Hubble types, smaller half-light radii, and larger central surface mass densities than the multi-armed galaxies. Lower mass galaxies of both arm classes have later Hubble types and lower concentrations than higher mass galaxies. In our sample, a higher fraction of grand design galaxies have classical bulges rather than pseudo-bulges, compared to multi-armed galaxies. These results are consistent with theoretical models and simulations which suggest that dense classical bulges support the development and/or longevity of 2-armed spiral patterns. Similar specific star formation rates are found in multi-armed and grand design galaxies with similar stellar masses and concentrations. This implies that the specific star formation rates in spiral galaxies is a function of concentration and stellar mass, but independent of the number of spiral arms. Our classifications are consistent with arm counts from the Galaxy Zoo 2 project and published m=3 Fourier amplitudes.

astro-ph.GA↗

arXiv2022

The Effect of Environment on Galaxy Spiral Arms, Bars, Concentration, and Quenching

For a sample of 4378 nearby spiral and S0 galaxies, Yu and Ho (2020) used Fourier analysis of Sloan Digital Sky Survey images to show that the strengths of the spiral arms and the pitch angles of the arms are inversely correlated with central concentration. In the current study, we search for trends in the Yu and Ho (2020) spiral arm parameters with environment and specific star formation rate (sSFR). When comparing galaxies with similar concentrations, we do not find a significant difference in the arm strengths or pitch angles of spiral galaxies in clusters compared to field galaxies. When differences in concentration are taken into account, we also find no significant difference in the parameter f3 for cluster spirals compared to field spirals, where f3 is the normalized m = 3 Fourier amplitude. When concentration is held fixed, both arm strength and pitch angle are correlated with sSFR, but f3 is not. These relations support the suggestion by Davis et al. (2015) of a `fundamental plane' of spiral structure involving pitch angle, bulge stellar mass, and gas surface density. We discuss these results in terms of theories of spiral arm production and quenching in galaxies. To aid comparison with earlier studies based on Galaxy Zoo, we explore how the Yu and Ho (2020) parameters relate to similar parameters measured by Galaxy Zoo (i.e., f3 vs. number of arms, pitch angle vs. winding parameter, and concentration vs. bulge class).

astro-ph.GA↗

arXiv2020

Revealing the Double Nucleus of NGC 4490

NGC 4490/85 (UGC 7651/48) or Arp 269 is well known for being one of the closest interacting/merging galactic systems. NGC 4490 has a high star formation rate (SFR) and is surrounded by an enormous HI feature stretching about 60 kpc north and south of the optically visible galaxies. Both the driver for the high SFR in NGC 4490 and the formation mechanism of the HI structure are puzzling aspects of this system. We have used mid-infrared Spitzer data to show that NGC 4490 has a double nucleus morphology. One nucleus is visible in the optical, while the other is only visible at infrared and radio wavelengths. We find the optical nucleus and the potential infrared visible nucleus have similar sizes, masses, and luminosities. Both are comparable in mass and luminosity to other nuclei found in interacting galaxy pairs and much more massive and luminous compared with typical non-nuclear star-forming complexes. We examine possible origin scenarios for the infrared feature, and conclude that it is likely that NGC 4490 is itself a merger remnant, which is now interacting with NGC 4485. This earlier encounter provides both a possible driver for extended star formation in NGC 4490, and multiple pathways for the formation of the extended HI plume.

astro-ph.GA↗

arXiv2019

The Hot Gas Exhaust of Starburst Engines in Mergers: Testing Models of Stellar Feedback and Star Formation Regulation

Using archival data from the Chandra X-ray telescope, we have measured the spatial extent of the hot interstellar gas in a sample of 49 nearby interacting galaxy pairs, mergers, and merger remnants. For systems with SFR > 1 M(sun)/yr, the volume and mass of hot gas are strongly and linearly correlated with the star formation rate (SFR). This supports the idea that stellar/supernovae feedback dominates the production of hot gas in these galaxies. We compared the mass of X-ray-emitting hot gas Mx(gas) with the molecular and atomic hydrogen interstellar gas masses in these galaxies (M(H2) and M(HI), respectively), using published carbon monoxide and 21 cm HI measurements. Systems with higher SFRs have larger Mx(gas)/(M(H2) + M(HI)) ratios on average, in agreement with recent numerical simulations of star formation and feedback in merging galaxies. The Mx(gas)/(M(H2) + M(HI)) ratio also increases with dust temperature on average. The ratio Mx(gas)/SFR is anti-correlated with the IRAS 60 micron to 100 micron flux ratio and with the Spitzer 3.6 micron to 24 micron. These trends may be due to variations in the spatial density of young stars, the stellar age, the ratio of young to old stars, the initial mass function, and/or the efficiency of stellar feedback. Galaxies with low SFR (<1 M(sun)/yr) and high K band luminosities may have an excess of hot gas relative to the relation for higher SFR galaxies, while galaxies with low K band luminosities (and therefore low stellar masses) may have a deficiency in hot gas, but our sample is not large enough for strong statistical significance.

astro-ph.GA↗

arXiv2018

Stellar Population Synthesis of star forming clumps in galaxy pairs and non-interacting spiral galaxies

We have identified 1027 star forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in $8\rm{μm}$ observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution (SED) of our clumps with the Code Investigating GALaxy Emission (CIGALE) using a double exponentially declined star formation history (SFH). We derive SFRs, stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an AGN for these clumps. The resolved star formation main sequence holds on 2.5kpc scales, although it does not hold on 1kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that SFR is enhanced through the disk and in the tidal features relative to normal spirals.

astro-ph.GA↗

arXiv2017

Diffuse X-ray-emitting Gas in Major Mergers

Using archived data from the Chandra X-ray telescope, we have extracted the diffuse X-ray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L(X)(gas)) with the global star formation rate (SFR). After correction for absorption within the target galaxy, we do not see strong trend of L(X)(gas)/SFR with SFR or merger stage for galaxies with SFR > 1 M(sun) yr^-1. For these galaxies, the median L(X)(gas)/SFR is 5.5 X 10^39 ((erg s^-1)/M(sun) yr^-1)), similar to that of normal spiral galaxies. These results suggest that stellar feedback in star forming galaxies reaches an approximately steady state condition, in which a relatively constant fraction of about 2% of the total energy output from supernovae and stellar winds is converted into X-ray flux. Three late-stage merger remnants with low SFRs and high K band luminosities (L(K)) have enhanced L(X)(gas)/SFR; their UV/IR/optical colors suggest that they are post-starburst galaxies, perhaps in the process of becoming ellipticals. Systems with L(K) < 10^10 L(sun) have lower L(X)(gas)/SFR ratios than the other galaxies in our sample, perhaps due to lower gravitational fields or lower metallicities. We see no relation between L(X)(gas)/SFR and Seyfert activity in this sample, suggesting that feedback from active galactic nuclei is not a major contributor to the hot gas in our sample galaxies.

astro-ph.GA↗

arXiv2016

A Comparative Study of Knots of Star Formation in Interacting vs. Spiral Galaxies

Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published H-alpha images, we have compared the star formation rates of ~700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high star formation rates than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The star formation rates of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest star formation rates, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to H-alpha, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in H-alpha. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus the star forming regions in interacting galaxies are more luminous, dustier, or younger on average.

astro-ph.GA↗

arXiv2014

Evidence of a Mira-like tail and bow shock about the semi-regular variable V CVn from four decades of polarization measurements

Polarization is a powerful tool for understanding stellar atmospheres and circumstellar environments. Mira and semi-regular variable stars have been observed for decades and some are known to be polarimetrically variable, however, the semi-regular variable V Canes Venatici displays an unusually large, unexplained amount of polarization. We present ten years of optical polarization observations obtained with the HPOL instrument, supplemented by published observations spanning a total interval of about forty years for V CVn. We find that V CVn shows large polarization variations ranging from 1 - 6%. We also find that for the past forty years the position angle measured for V CVn has been virtually constant suggesting a long-term, stable, asymmetric structure about the star. We suggest that this asymmetry is caused by the presence of a stellar wind bow shock and tail, consistent with the star's large space velocity.

astro-ph.SR↗

arXiv2014

Extra-Nuclear Starbursts: Young Luminous Hinge Clumps in Interacting Galaxies

Hinge clumps are luminous knots of star formation near the base of tidal features in some interacting galaxies. We use archival Hubble Space Telescope UV/optical/IR images and Chandra X-ray maps along with GALEX UV, Spitzer IR, and ground-based optical/near-IR images to investigate the star forming properties in a sample of 12 hinge clumps in five interacting galaxies. The most extreme of these hinge clumps have star formation rates of 1 - 9 M(sun)/yr, comparable to or larger than the `overlap' region of intense star formation between the two disks of the colliding galaxy system the Antennae. In the HST images, we have found remarkably large (~70 pc) and luminous (M(I) ~ 12.2 to -16.5) sources at the centers of these hinge clumps, sometimes embedded in a linear ridge of fainter star clusters. We have found strong X-ray emission from several of these hinge clumps. In most cases, this emission is well-resolved with Chandra and has a thermal X-ray spectrum, thus it is likely due to hot gas associated with the star formation. The ratio of the extinction-corrected diffuse X-ray luminosity to the mechanical energy rate (the X-ray production efficiency) for the hinge clumps is similar to that in the Antennae galaxies, but higher than those for regions in the normal spiral galaxy NGC 2403. Two of the hinge clumps have point-like X-ray emission much brighter than expected for hot gas; these sources are likely `ultra-luminous X-ray sources' (ULXs) due to accretion disks around black holes. The most extreme of these sources, in Arp 240, has a hard X-ray spectrum and an absorbed X-ray luminosity of ~2 X 10^41 erg/s; more than expected by single high mass X-ray binaries (HMXBs), thus it may be either a collection of HMXBs or an intermediate-mass black hole (>=80 M(sun)). [ abridged ]

astro-ph.GA↗

arXiv2013

UV/Optical/IR Color Sequences Along the Tidal Ring/Arm of Arp 107

We construct UV/optical/IR spectral energy distributions for 29 star forming regions in the interacting galaxy Arp 107, using GALEX UV, Sloan Digitized Sky Survey optical, and Spitzer infrared images. In an earlier study utilizing only the Spitzer data, we found a sequence in the mid-infrared colors of star-forming knots along the strong tidal arm in this system. In the current study, we find sequences in the UV/optical colors along the tidal arm that mirror those in the mid-infrared, with blue UV/optical colors found for regions that are red in the mid-infrared, and vice versa. With single-burst stellar population synthesis models, we find a sequence in the average stellar age along this arm, with younger stars preferentially located further out in the arm. Models that allow two populations of different ages and dust attenuations suggest that there may be both a young component and an older population present in these regions. Thus the observed color sequences may be better interpreted as a sequence in the relative proportion of young and old stars along the arm, with a larger fraction of young stars near the end. Comparison with star forming regions in other interacting galaxies shows that the Arp 107 regions are relatively quiescent, with less intense star formation than in many other systems.

astro-ph.CO↗

arXiv2012

ChAInGeS: The Chandra Arp Interacting Galaxies Survey

We have conducted a statistical analysis of the ultra-luminous X-ray point sources (ULXs; L(X) >= 10^39 erg/s) in a sample of galaxies selected from the Arp Atlas of Peculiar Galaxies. We find a possible enhancement of a factor of ~2-4 in the number of ULXs per blue luminosity for the strongly interacting subset. Such an enhancement would be expected if ULX production is related to star formation, as interacting galaxies tend to have enhanced star formation rates on average. For most of the Arp galaxies in our sample, the total number of ULXs compared to the far-infrared luminosity is consistent with values found earlier for spiral galaxies. This suggests that for these galaxies, ULXs trace recent star formation. However, for the most infrared-luminous galaxies, we find a deficiency of ULXs compared to the infrared luminosity. For these very infrared-luminous galaxies, AGNs may contribute to powering the far-infrared; alternatively, ULXs may be highly obscured in the X-ray in these galaxies and therefore not detected by these Chandra observations. We determined local UV/optical colors within the galaxies in the vicinity of the candidate ULXs using GALEX UV and SDSS optical images. In most cases, the distributions of colors are similar to the global colors of interacting galaxies. However, the u - g and r - i colors at the ULX locations tend to be bluer on average than these global colors, suggesting that ULXs are preferentially found in regions with young stellar populations. In the Arp sample there is a possible enhancement of a factor of ~2 - 5 in the fraction of galactic nuclei that are X-ray bright compared to more normal spirals.

astro-ph.CO↗

arXiv2012

The symmetries and scaling of tidal tails in galaxies

(Abriged) We present analytic models for the formation and evolution of tidal tails and related structures following impulsive disturbances in galaxy collisions. Since the epicyclic approximation is not valid for large radial excursions, we use orbital equations of the form we call p-ellipses. These have been shown to provide accurate representations of orbits in power-law halo potentials. In the case of a purely tidal disturbance the resulting tidal tails have simple structure. Scalings for their maximum lengths and other characteristics as functions of the tidal amplitude and the exponent of the power-law potentials are described. The analytic model shows that azimuthal caustics (orbit crossing zones) are produced generically in these tails at a fixed azimuth relative to the point of closest approach. Long tails, with high order caustics at their base are also produced at larger amplitudes. The analysis is extended to nonlinear disturbances and multiple encounters, which break the symmetries of tidal perturbations. As the strength of the nonlinear terms is varied the structure of the resulting forms varies from symmetric tails to one-armed plumes. Cases with two or more impulse disturbances are also considered as the simplest analytic models distinguishing between prograde and retrograde encounters. A specific mechanism for the formation of tidal dwarf galaxies at the end of tails is suggested as a consequence of resonance effects in prolonged encounters. Qualitative comparisons to Arp Atlas systems suggest that the limiting analytic cases are realized in real systems. We identify a few Arp systems which may have swallowtail caustics, where dissipative gas streams converge and trigger star formation. UV and optical images reveal luminous knots of young stars at these 'hinge clump' locations.

astro-ph.CO↗

arXiv2010

The Larson-Tinsley Effect in the UV: Interacting vs. `Normal' Spiral Galaxies

We compare the UV-optical colors of a well-defined set of optically-selected pre-merger interacting galaxy pairs with those of normal spirals. The shorter wavelength colors show a larger dispersion for the interacting galaxies than for the spirals. This result can best be explained by higher star formation rates on average in the interacting galaxies, combined with higher extinctions on average. This is consistent with earlier studies, that found that the star formation in interacting galaxies tends to be more centrally concentrated than in normal spirals, perhaps due to gas being driven into the center by the interaction. As noted in earlier studies, there is a large variation from galaxy to galaxy in the implied star formation rates of the interacting galaxies, with some galaxies having enhanced rates but others being fairly quiescent.

astro-ph.CO↗

arXiv2010

Spirals, Bridges, and Tails: A GALEX UV Atlas of Interacting Galaxies

We have used the GALEX ultraviolet telescope to study stellar populations and star formation morphology in a well-defined sample of 42 nearby optically-selected pre-merger interacting galaxy pairs. Galaxy interactions were likely far more common in the early Universe than in the present, thus our study provides a nearby well-resolved comparison sample for high redshift studies. We have combined the GALEX NUV and FUV images with broadband optical maps from the Sloan Digitized Sky Survey to investigate the ages and extinctions of the tidal features and the disks. The distributions of the UV/optical colors of the tidal features and the main disks of the galaxies are similar, however, the tidal features are bluer on average in NUV - g when compared with their own parent disks, thus tails and bridges are often more prominent relative to the disks in UV images compared to optical maps. This effect is likely due to enhanced star formation in the tidal features compared to the disks rather than reduced extinction, however, lower metallicities may also play a role. We have identified a few new candidate tidal dwarf galaxies in this sample. Other interesting morphologies such as accretion tails and `beads on a string' are also seen in these images. We also identify a possible `Taffy' galaxy in our sample, which may have been produced by a head-on collision between two galaxies. In only a few cases are strong tidal features seen in HI maps but not in GALEX.

astro-ph.CO↗