Nearby Low Surface Brightness Research Articles

Delayed Stellar Mass Assembly in the Low Surface Brightness Dwarf Galaxy KDG 215∗

Abstract We present H i spectral line and optical broadband images of the nearby low surface brightness dwarf galaxy KDG 215. The H i images, acquired with the Karl G. Jansky Very Large Array, reveal a dispersion-dominated interstellar medium with only weak signatures of coherent rotation. The H i gas reaches a peak mass surface density of 6 M ⊙ pc−2 at the location of the peak surface brightness in the optical and the ultraviolet. Although KDG 215 is gas-rich, the Hα non-detection implies a very low current massive star formation rate. In order to investigate the recent evolution of this system, we have derived the recent and lifetime star formation histories from archival Hubble Space Telescope images. The recent star formation history shows a peak star formation rate ∼1 Gyr ago, followed by a decreasing star formation rate to the present day quiescent state. The cumulative star formation history indicates that a significant fraction of the stellar mass assembly in KDG 215 has occurred within the last 1.25 Gyr. KDG 215 is one of only a few known galaxies that demonstrates such a delayed star formation history. While the ancient stellar population (predominantly red giants) is prominent, the look-back time by which 50% of the mass of all stars ever formed had been created is among the youngest of any known galaxy.

A study of the H i and optical properties of Low Surface Brightness galaxies: spirals, dwarfs, and irregulars

We present a study of the H i and optical properties of nearby (z ≤ 0.1) Low Surface Brightness galaxies (LSBGs). We started with a literature sample of ∼900 LSBGs and divided them into three morphological classes: spirals, irregulars, and dwarfs. Of these, we could use ∼490 LSBGs to study their H i and stellar masses, colours, and colour–magnitude diagrams, and local environment, compare them with normal, High Surface Brightness (HSB) galaxies and determine the differences between the three morphological classes. We found that LSB and HSB galaxies span a similar range in H i and stellar masses, and have a similar |$M_{\rm H\, \small {I}}$|/M⋆–M⋆ relationship. Among the LSBGs, as expected, the spirals have the highest average H i and stellar masses, both of about 109.8 M⊙. The LSGBs’ (g − r) integrated colour is nearly constant as function of H i mass for all classes. In the colour–magnitude diagram, the spirals are spread over the red and blue regions whereas the irregulars and dwarfs are confined to the blue region. The spirals also exhibit a steeper slope in the |$M_{\rm H\, \small {I}}$|/M⋆–M⋆ plane. Within their local environment, we confirmed that LSBGs are more isolated than HSB galaxies, and LSB spirals more isolated than irregulars and dwarfs. Kolmogorov–Smirnov statistical tests on the H i mass, stellar mass, and number of neighbours indicate that the spirals are a statistically different population from the dwarfs and irregulars. This suggests that the spirals may have different formation and H i evolution than the dwarfs and irregulars.

SDSS J121811.0+465501.2: A New Low Surface Brightness Galaxy with Low Metallicity

We serendipitously find a new nearby Low Surface Brightness (LSB) galaxy from SDSS database. We estimate oxygen abundance of its H II region SDSS J121811.0+465501.2 from electron temperature, as well as for another H II region, SDSS J135440.5+535309.6, located in irregular LSB galaxy UGC 8837. These two extragalactic H II regions were classified as stars in the SDSS-DR4 database, and were found occasionally by us in the automatic recognition and classification on stellar spectra.Their optical spectra show obvious emission lines, i.e., strong [O III]4959, 5007, Balmer emission lines, but very weak [N II]6548,6583 and [S II]6317,6731, which could indicate that they are metal-poor star-forming regions. The derived oxygen abundances of the two objects are 12+log(O/H) ~ 7.88+-0.30 and 7.70+-0.30, respectively. The host of the H II region SDSS J121811.0+465501.2 is identified as a new nearly edge-on LSB disc galaxy (almost without bulge) with the B-band central surface brightness mu_0(B) as 23.68 mag arcsec^{-2} and inclination angle as ~75 degree by using the GIM2D software to analyze its g- and r-band images independently. It is a nearby dwarf galaxy with redshift z~0.00157, disk scale-length ~0.40 kpc and B-band absolute magnitude M_B ~ -13.51 mag. The very low oxygen abundances of these two objects confirm the low metallicities of LSB galaxies.

H I in extremely metal deficient galaxies - III. Giant Metrewave Radio Telescope observations of blue compact galaxy HS 0822+3542

We present the results of Giant Metrewave Radio Telescope H i 21-cm line observations of the extremely metal deficient (XMD) blue compact galaxy (BCG) HS 0822+3542. HS 0822+3542 is the smallest known XMD galaxy; from Hubble Space Telescope (HST) imaging, it has been suggested that it actually consists of two still smaller (∼100 pc sized) ultra-compact dwarfs that are in the process of merging. The brighter of these two putative ultra-compact dwarfs has an ocular appearance, similar to that seen in galaxies that have suffered a penetrating encounter with a smaller companion. From our H i imaging, we find that the gas distribution and kinematics in this object are similar to that of other low-mass galaxies, albeit with some evidence for tidal disturbance. On the other hand, the H i emission has an angular size ∼25 times larger than that of the putative ultra-compact dwarfs. The optical emission is also offset from the centre of the H i emission. HS 0822+3542 is located in the nearby Lynx–Cancer void, but has a nearby companion low surface brightness dwarf galaxy SAO 0822+3545. In light of all this, we also consider a scenario where the optical emission from HS 0822+3542 comes not from two merging ultra-compact dwarfs but from multiple star-forming regions in a tidally disturbed galaxy. In this model, the ocular appearance of the brighter star-forming region could be the result of triggered star formation.

Morphology and star formation in nearby low surface brightness galaxies

We present observations (B, R, K, Hα and H i) of six nearby low surface brightness galaxies (LSBGs). They show an astonishing amount of variety; while some systems appear smooth and featureless, others resolve into loose assemblies of gas clouds. We have derived rotation curves, gas surface density profiles and star formation thresholds for three of the galaxies. The results have been used to test two ideas describing their star formation: one in which star formation depends solely on the H i gas surface density, and one that depends on differential rotation. We find that a critical H i surface density criterion in the range 2.6–12.6 × 10(20) cm(−2) (2.1–10.1 M⊙ pc(−2)) best describes the star-forming ability of these galaxies on local and global scales. A critical gas surface density based on the rotation of the gas is also able to describe the results on a global scale for two of the three galaxies for which we were able to derive rotation curves.

Hubble Space Telescope imaging of globular cluster candidates in low surface brightness dwarf galaxies

Fifty-seven nearby low surface brightness dwarf galaxies (−10 > MV > −16) were searched for globular cluster candidates (GCCs) using Hubble Space Telescope WFPC2 imaging in V and I. The sample consists of 18 dwarf spheroidal (dSph), 36 irregular (dIrr), and 3 “transition” type (dIrr/dSph) galaxies with angular sizes less than 3.7 kpc situated at distances 2−6 Mpc in the field and in the nearby groups: M 81, Centaurus A, Sculptor, Canes Venatici I cloud. We find that ∼50% of dSph, dIrr/dSph, and dIrr galaxies contain GCCs. The fraction of GCCs located near the center of dwarf spheroidal galaxies is >2 times higher than for dIrrs. The mean integral color of GCCs in dSphs, (V − I)0 = 1.04 ± 0.16 mag, coincides with the corresponding value for Galactic globular clusters and is similar to the blue globular cluster sub-populations in massive early-type galaxies. The color distribution for GCCs in dIrrs shows a clear bimodality with peaks near (V − I)0 = 0.5 and 1.0 mag. Blue GCCs are presumably young with ages t −6.5 mag in both dSph and dIrr galaxies, reminiscent of excess populations of faint globular clusters in nearby Local Group spiral galaxies. The measurement of structural parameters using King-profile fitting reveals that most GCCs have structural parameters similar to extended outer halo globular clusters in the Milky Way and M 31, as well as the recently discovered population of “faint fuzzy” clusters in nearby lenticular galaxies.

Globular clusters in low mass galaxies

We study properties of globular cluster candidates (GCCs) and the diffuse stellar populations in nearby low surface brightness dwarf galaxies, using HST WFPC2 photometry in the V and I bands. Our sample consists of 18 dwarf spheroidal (dSph), 36 dwarf irregular (dIrr), and 3 transition-type galaxies, with projected linear diameters less than 3.5 kpc and mean blue surface brightness mag. There is a tendency of increasing half-light radii with increasing projected galactocentric distances for a large number of GCCs in dSph galaxies, which is also observed in the Galactic globular cluster system. We embarked on a spectroscopic survey of GCCs in low-mass galaxies to obtain their chemical compositions and relative ages.

An optical velocity for the Phoenix dwarf galaxy

We present the results of a VLT observing program carried out in service mode using FORS1 on ANTU in Long Slit mode to determine the optical velocities of nearby low surface brightness galaxies. As part of our program of service observations we obtained long-slit spectra of several members of the Phoenix dwarf galaxy from which we derive an optical helio-centric radial velocity of -13 +/- 9km/s. This agrees very well with the velocity of the most promising of the HI clouds seen around Phoenix, which has a helio-centric velocity of -23 km/s, but is significantly different to the recently published optical heliocentric velocity of Phoenix of -52 +/- 6 km/s of Gallart et al. (2001).

HI with the GMRT

The Giant Metrewave Radio Telescope (GMRT) has recently come into operation. This paper reports on observations of the HI line made using the GMRT during its commissioning phase. These include observations of the nearby Low Surface brightness galaxy Cepheus 1, as well as of a number of low and medium redshift damped Ly-α systems. The derived spin temperatures for these systems is typically higher than that characteristic of the gas in the disk of the Galaxy. Higher spin temperatures were known to be characteristic of high redshift damped Ly-α absorbers, and had been earlier attributed to evolutionary effects. Our observations suggest that high spin temperatures are not a consequence of evolutionary effects since the look back time to these low z absorbers is modest. We also report on the short time scale (days) variability of the absorption profile of the z = 0.3127 system in front of B1127-145. This is the second damped Ly-α system to show such variation (the other being the z = 0.524 absorber in front of AO 0235+164).

Damped [CLC]Lyα[/CLC] Absorption from a Nearby Low Surface Brightness Galaxy

Ground-based & HST images of the nearby galaxy SBS 1543+593 (z=0.009) show it to be a Low Surface Brightness (LSB) galaxy with a central surface brightness of mu_B(0)=23.2 mag/arcsec-2 and scale length 0.9 h-1 kpc, values typical for the local LSB galaxy population. The galaxy lies directly in front of the QSO HS 1543+5921 (z=0.807); an HST STIS spectrum of the quasar reveals a damped Lyman-alpha (DLA) line at the redshift of the interloper with an HI column density of log N(HI) = 20.35, as well as several low-ionization metal lines with strengths similar to those found in the Milky Way interstellar medium. Our data show that LSB galaxies are certainly able to produce the DLA lines seen at higher redshift, and fuels the speculation that LSB galaxies are a major contributor to that population of absorbers.

The optical velocity of the Antlia dwarf galaxy

We present the results of a Very Large Telescope observing programme carried out in service mode using fors1 on ANTU (UT1) in long slit mode to determine the optical velocities of nearby low surface brightness galaxies. Outlying Local Group galaxies are of paramount importance in placing constraints on the dynamics and thus on both the age and the total mass of the Local Group. Optical velocities are also necessary to determine if the observations of H i gas in and around these systems are the result of gas associated with these galaxies or a chance superposition with high-velocity H i clouds or the Magellanic Stream. The data were of a sufficient signal-to-noise ration to enable us to obtain a reliable result in one of the galaxies we observed – Antlia – for which we have found an optical heliocentric radial velocity of 351±15 km s−1.

Hubble Space TelescopePhotometry of the Dwarf Spheroidal Galaxy ESO 410‐G005

We present Hubble Space Telescope WFPC2 imaging of the nearby low surface brightness dwarf spheroidal galaxy ESO 410-G005, which has been resolved into stars for the first time. The resulting color-magnitude diagram for about 2500 stars shows a red giant branch with a tip at I = 22.4 ± 0.15 mag, which yields a distance of DMW = 1.9 ± 0.2 Mpc. ESO 410-G005 is found to be metal-poor with a mean metallicity of ⟨[Fe/H]⟩ = (-1.8 ± 0.4) dex estimated from its red giant branch. Upper asymptotic giant branch stars appear to be present near the center of the galaxy, indicative of a substantial, centrally concentrated intermediate-age population, unless these objects are artifacts of crowding. Previous studies did not detect ESO 410-G005 in Hα or in H I. Based on our distance estimate, ESO 410-G005 is a probable member of the Sculptor group of galaxies. Its linear separation from the nearest spiral, NGC 55, is 230 kpc on the sky. The deprojected separation ranges from 340 to 615 kpc depending on the assumed distance of NGC 55. The deprojected distance from the Sculptor group spiral NGC 300 is (385 ± 200) kpc. ESO 410-G005 appears to be a relatively isolated dSph within the Sculptor group. Its absolute magnitude, MV,0 = -12.1 ± 0.2 mag, its central surface brightness, μV,0 = 22.7 ± 0.1 mag arcsec-2, and its mean metallicity, [Fe/H] = (-1.8 ± 0.4) dex follow the trend observed for dwarf galaxies in the Local Group.

Nearby Gas‐rich Low Surface Brightness Galaxies

We examine the Fisher-Tully cz < 1000 km s-1 galaxy sample to determine whether it is a complete and representative sample of all galaxy types, including low surface brightness populations, as has been recently claimed. We find that the sample is progressively more incomplete for galaxies with (1) smaller physical diameters at a fixed isophote and (2) lower H I masses. This is likely to lead to a significant undercounting of nearby gas-rich low surface brightness galaxies. However, through comparisons to other samples, we can understand how the nearby galaxy counts need to be corrected, and we see some indications of environmental effects that probably result from the local high density of galaxies.

The Morphology of Nearby Low Surface Brightness Galaxies

It is commonly assumed that low surface brightness (LSB) galaxies are dormant and quiescent systems. These conclusions are however based on observations of a large number of distant LSB galaxies. Here we show some first results of a study of very nearby galaxies, which suggest that the featureless systems observed at large distances resolve into complex and chaotic systems. We also present new data on NGC 6822, a dwarf galaxy in our Local Group, and argue that this object would be classified as a LSB galaxy if it were at a larger distance. It thus puts us in the unique position of being able to study a LSB galaxy at very high resolution, enabling us to get a better picture of the interaction between ISM, stars and dark matter in low density galaxies.

VLA HI Imaging of the Low Surface Brightness Dwarf Galaxy DDO 47

AbstractWe present high resolution VLA-observations of the nearby Low Surface Brightness Dwarf Galaxy DDO 47. This object shows many hole-like structures in its neutral interstellar medium. The majority of the detected H I-shells are found to be expanding. Their origin is therefore believed to be due to stellar winds of the most massive stars and their subsequent supernova (SN type II) explosions within regions of recent star formation (SF). Current SF in DDO 47 is predominantly present on the rims of the HI-shells suggesting propagating SF. At a projected distance of 20 kpc (adopting a distance to DDO 47 of 4 Mpc), a companion galaxy was detected at almost the same systemic velocity (DDO 47 B). A search for an optical identification suggests that CGCG 087-033 is the optical counterpart of the companion. A preliminary dynamical analysis based on DDO 47’s rotation curve yields that it is dark matter dominated (about 80% of its dynamical mass is in some non-visible form). A simple mass model suggests that DDO 47 is one of the ‘thickest’ dwarf galaxies studied so far.

Discovery of a Nearby Low Surface Brightness Spiral Galaxy

During the course of a search for compact, isolated gas clouds moving with anomalous velocities in or near our own Galaxy, we have discovered in the data of the Leiden/Dwingeloo survey of Galactic hydrogen the H I signature of a large galaxy moving at a recession velocity of 282 km s-1 with respect to our Galaxy. Deep multicolor and spectroscopic optical observations show the presence of star formation in scattered H II regions; radio H I synthesis interferometry confirms that the galaxy is rich in H I and has the rotation signature of a spiral galaxy; a submillimeter observation failed to detect the CO molecule. The radio and optical evidence combined suggest its classification as a low surface brightness (LSB) spiral galaxy. It is located in close spatial and kinematic proximity to the galaxy NGC 6946. The newly discovered galaxy, which we call Cep 1, is at a distance of about 6 Mpc. It is probably to be numbered among the nearest few LSB spiral galaxies.

ITAL]Hubble[/ITAL] [ITAL]Space[/ITAL] [ITAL]Telescope[/ITAL] Wide Field Planetary Camera 2 Imaging of UGC 12695: A Remarkably Unevolved Galaxy at Low Redshift

Utilizing the F814W and F300W filters, short-exposure Hubble Space Telescope Wide Field Planetary Camera 2 images were taken of UGC 12695, a nearby (z ~ 0.021) low surface brightness disk galaxy. UGC 12695 has an unusual morphology, consisting of a Y-shaped nucleus surrounded by a faint spiral arm with a number of bright H II regions interspersed throughout the galaxy. Surface photometry indicates that the majority of recent star formation in this galaxy occurred in these very localized regions, most of which have a radius of 2''. This uneven stellar distribution, combined with the galaxy's overall extremely blue color and low metallicity, indicates that UGC 12695 is an unevolved galaxy. Some of the structural peculiarities of this galaxy arise because a number of background galaxies, previously thought to be morphological components of this galaxy, are showing through both the outer nucleus and spiral arms of UGC 12695. Surface photometry of these galaxies shows them to be fairly small (α < 18) disk galaxies with total magnitudes ranging from 19.6 through 24.2 mag and central surface brightnesses in the range 20.2 mag arcsec-2 ≤ μ(0) ≤ 23.1 mag arcsec-2. When possible, the U, B, V, and I colors of these galaxies were measured using ground-based images, which show the galaxies to be fairly red, indicating that they are likely at redshifts z ≥ 0.5. Inclusion of them in the photometry of UGC 12695 makes the galaxy appear significantly redder. When these galaxies are masked out, the resultant U-I color of UGC 12695 is -0.2 ± 0.1, making it perhaps the bluest galaxy ever measured in this color system and confirming its nature as a very unevolved galaxy at low redshift. Spectroscopy of these background galaxies, through the transparent disk of UGC 12695, may help to clarify its chemical evolution and current heavy-element content.

A Parsec-Size Bow Shock around Betelgeuse

view Abstract Citations (64) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Parsec-Size Bow Shock around Betelgeuse Noriega-Crespo, Alberto ; van Buren, Dave ; Cao, Yu ; Dgani, Ruth Abstract We present new High Resolution IRAS (HiRes) images at 60 and 100 \mum of a bow shock or shell with a mean radius of 6arcmin surrounding Betelgeuse (alpha Orionis). The outermost section of this structure is at ~ 7arcmin which corresponds to a physical scale of 0.8 pc at a distance of 400 pc. The images were made by applying a relative Burg entropy maximization algorithm to suppress the ringing around bright sources and allow the detection of nearby low surface brightness features. The shell is relatively narrow at 60 \mum (at the 1arcmin HiRes resolution), asymmetric and oriented along the star's direction of motion. We propose that the shell is confined by the ram pressure of the interstellar medium. Using a shell flux of 110 Jy (at 60 \mum) within a radius of 7.arcmin5 we estimate mass of 0.14 \msol for the shell. Publication: The Astronomical Journal Pub Date: August 1997 DOI: 10.1086/118517 Bibcode: 1997AJ....114..837N Keywords: TURBULENCE; ISM: STRUCTURE; STARS: INDIVIDUAL: BETELGEUSE full text sources ADS | data products SIMBAD (1)

Where Are the Nearby Gas-rich Low Surface Brightness Galaxies?

The Fisher-Tully (F-T) ''10 Mpc Catalog of Late-Type Galaxies'' is remarkably complete. Despite the considerable effort that has been spent searching for and cataloging low surface brightness (LSB) galaxies, almost no new HI-rich galaxies have been added to the volume to which the F-T observations were both sensitive [d <10(M-HI/10(8.2) M-.)(5/12) Mpc] and intended to be complete (d <10 Mpc). It has not yet been demonstrated by the new surveys that HI-rich LSB galaxies are not properly represented in this catalog of nearby galaxies. Although new optical surveys are discovering heretofore uncataloged galaxies at greater distances than the depth of the F-T catalog, they do not alter the completeness of the F-T catalog for H I-rich LSB objects. Thus, unless the galaxy population of the local volume is atypical, there is at present no evidence for a significant, new population of gas-rich galaxies that has escaped recognition until now.

The Contribution of Low Surface Brightness Galaxies to Faint Galaxy Counts

view Abstract Citations (80) References (90) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Contribution of Low Surface Brightness Galaxies to Faint Galaxy Counts Ferguson, Henry C. ; McGaugh, Stacy S. Abstract Recent observations have revealed a population of blue galaxies at intermediate redshift with a space density well in excess of expectations from the local luminosity function and standard cosmology. The colors and luminosities of these faint blue galaxies are similar to nearby low surface brightness (LSB) galaxies. Such galaxies are severely underrepresented in surveys used to define the local luminosity function, but could in principle be detected in deep surveys. If LSB galaxy density is high enough, the faint-galaxy counts could be explained without requiring rapid galaxy evolution. To explore the consequences of including LSB galaxies, we construct catalogs of simulated nonevolving galaxies drawn from a multivariate distribution of galaxy luminosities, central surface brightnesses, bulge/disk ratios, and spectral-energy distributions. We compare two models dominated by LSB galaxies to a "standard" nonevolving model. Model galaxies are convolved with seeing and selected in a manner that closely matches real surveys. For each model we compute the local Bj band luminosity function, H I mass function, number counts in the Bj, I, and K bands, redshift distributions and color distributions. We find it possible to include a large population of LSB galaxies and incorporate a steep faint-end slope of the luminosity function in our simulations without violating the constraints on the local field-galaxy luminosity function or the H I mass function. For q0 = 0.5, the most favorable model matches the counts to B = 23, but falls short of the observations at fainter magnitudes. The discrepancy at faint magnitudes is smaller in the I and K bands. The colors and redshift distributions remain roughly consistent with observations to B = 24. The most serious discrepancy with observations is in the distribution of re at faint magnitudes, suggesting that the model contains too many LSB galaxies. Nevertheless, the results suggest that LSB galaxies could be a significant contributor to faint-galaxy counts, reducing the need for such extreme models of galaxy evolution as rapid merging or bursting dwarf galaxies. We propose several tests to assess the contribution of LSB galaxies to faint galaxy counts and to differentiate models involving moderate galaxy evolution from models involving rapid merging or starbursts. Publication: The Astrophysical Journal Pub Date: February 1995 DOI: 10.1086/175289 arXiv: arXiv:astro-ph/9409071 Bibcode: 1995ApJ...440..470F Keywords: COSMOLOGY: OBSERVATIONS; GALAXIES: LUMINOSITY FUNCTION; MASS FUNCTION; GALAXIES: PHOTOMETRY; Astrophysics E-Print: 39p, uuencoded compressed postscript, 18/21 figs included, full paper from http://planxty.stsci.edu:1024/ ferguson/lsb/lsbpp_b.ps,STScI 874 full text sources arXiv | ADS | data products SIMBAD (2)