scholarly journals Stellar populations of bulges in galaxies with a low surface-brightness disc

2012 ◽  
Vol 10 (H16) ◽  
pp. 340-340
Author(s):  
L. Morelli ◽  
E. M. Corsini ◽  
A. Pizzella ◽  
E. Dalla Bontà ◽  
L. Coccato ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Stellar Population ◽  
High Surface ◽  
Line Strength ◽  
Stellar Populations ◽  
Element Abundance ◽  
High Surface Brightness ◽  
Central Value ◽  
Radial Profiles ◽  
Low Surface Brightness

AbstractThe radial profiles of the Hβ, Mg, and Fe line-strength indices are presented for a sample of eight spiral galaxies with a low surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength indices and velocity dispersion are consistent to those known for early-type galaxies and bulges of high surface-brightness galaxies. The age, metallicity, and α/Fe enhancement of the stellar populations in the bulge-dominated region are obtained using stellar population models with variable element abundance ratios. Almost all the sample bulges are characterized by a young stellar population, on-going star formation, and a solar α/Fe enhancement. Their metallicity spans from high to sub-solar values. No significant gradient in age and α/Fe enhancement is measured, whereas only in a few cases a negative metallicity gradient is found. These properties suggest that a pure dissipative collapse is not able to explain formation of all the sample bulges and that other phenomena, like mergers or acquisition events, need to be invoked. Such a picture is also supported by the lack of a correlation between the central value and gradient of the metallicity in bulges with very low metallicity. The stellar populations of the bulges hosted by low surface-brightness discs share many properties with those of high surface-brightness galaxies. Therefore, they are likely to have common formation scenarios and evolution histories. A strong interplay between bulges and discs is ruled out by the fact that in spite of being hosted by discs with extremely different properties, the bulges of low and high surface-brightness discs are remarkably similar.

scholarly journals Stellar Populations of Dwarf Galaxies

1995 ◽  
Vol 164 ◽  
pp. 430-431
Author(s):  
Elchanan Almoznino ◽  
Noah Brosch
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxies ◽  
High Surface ◽  
Stellar Populations ◽  
Virgo Cluster ◽  
Original Sample ◽  
High Surface Brightness ◽  
Brightness Level ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

We selected a sample of dwarf galaxies in the Virgo cluster from the original catalog of Bingelli, Sandage and Tamman (1985), which have been measured at 21 cm by Hoffman et al. (1987). The original sample was selected to have both high surface brightness objects (classified as BCD or anything/BCD), and low surface brightness galaxies (classified as ImIII, ImIV or ImV). An additional selection was done on the total amount of HI, as given in Hoffman et al. We selected from each surface brightness group objects with high HI content (flux integral larger than a set threshold), and others with low HI content. We thus defined four samples differing in surface brightness level and total HI content.

scholarly journals Edge-on Low Surface Brightness Galaxies in the SDSS and the Red Halo Phenomenon

2006 ◽  
Vol 2 (S235) ◽  
pp. 82-82
Author(s):  
Brady Caldwell ◽  
Nils Bergvall
Keyword(s):  
Surface Brightness ◽  
Stellar Population ◽  
High Surface ◽  
Disk Galaxies ◽  
High Surface Brightness ◽  
Polar Direction ◽  
Low Surface Brightness ◽  
Compact Galaxies ◽  
Low Surface Brightness Galaxies ◽  
Lsb Galaxies

AbstractExtremely red halos have been detected around high surface brightness (HSB) disk galaxies and blue compact galaxies. We analyse the halo emission of a sample of 970 stacked edge-on low surface brightness (LSB) galaxies in the SDSS (DR4) down to μg ~ 30 mag arcsec−2. These are divided by g − r colour limits into a “blue” Sample A (336 galaxies), “yellow” Sample B (318 galaxies) and “red” Sample C (316 galaxies). The gri colours indicate a prominent red excess in the polar direction, strongly deviating from any normal stellar population.

scholarly journals Fossil group origins

2018 ◽  
Vol 618 ◽  
pp. A172 ◽  
Author(s):  
E. M. Corsini ◽  
L. Morelli ◽  
S. Zarattini ◽  
J. A. L. Aguerri ◽  
L. Costantin ◽  
...  
Keyword(s):  
Stellar Population ◽  
Line Strength ◽  
Abundance Ratio ◽  
Element Abundance ◽  
Population Parameters ◽  
Stellar Kinematics ◽  
Massive Galaxies ◽  
Radial Profiles ◽  
Major Merger ◽  
Satellite Galaxies

Context. Fossil groups (FGs) are galaxy aggregates with an extended and luminous X-ray halo, which are dominated by a very massive early-type galaxy and lack of L∗ objects. FGs are indeed characterized by a large magnitude gap between their central and surrounding galaxies. This is explained by either speculating that FGs are failed groups that formed without bright satellite galaxies and did not suffer any major merger, or by suggesting that FGs are very old systems that had enough time to exhaust their bright satellite galaxies through multiple major mergers. Aims. Since major mergers leave signatures in the stellar populations of the resulting galaxy, we study the stellar population parameters of the brightest central galaxies (BCGs) of FGs as a benchmark against which the formation and evolution scenarios of FGs can be compared. Methods. We present long-slit spectroscopic observations along the major, minor, and diagonal axes of NGC 6482 and NGC 7556, which are the BCGs of two nearby FGs. The measurements include spatially resolved stellar kinematics and radial profiles of line-strength indices, which we converted into stellar population parameters using single stellar-population models. Results. NGC 6482 and NGC 7556 are very massive (M∗ ≃ 1011.5 M⊙) and large (D25 ≃ 50 kpc) galaxies. They host a centrally concentrated stellar population, which is significantly younger and more metal rich than the rest of the galaxy. The age gradients of both galaxies are somewhat larger than those of the other FG BCGs studied so far, whereas their metallicity gradients are similarly negative and shallow. Moreover, they have negligible gradients of α-element abundance ratio. Conclusions. The measured metallicity gradients are less steep than those predicted for massive galaxies that formed monolithically and evolved without experiencing any major merger. We conclude that the observed FGs formed through major mergers rather than being failed groups that lacked bright satellite galaxies from the beginning.

High dispersion spectra of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 242-242
Author(s):  
S. Hyung ◽  
L. H. Aller
Keyword(s):  
Plasma Diagnostics ◽  
Surface Brightness ◽  
High Surface ◽  
Planetary Nebulae ◽  
High Dispersion ◽  
Chemical Compositions ◽  
Echelle Spectrograph ◽  
High Surface Brightness ◽  
Low Surface Brightness ◽  
Ngc 7662

Determinations of the plasma diagnostics and chemical compositions of planetary nebulae require ultimately high dispersion spectra. For objects of high surface brightness the Hamilton Echelle Spectrograph at Lick Observatory is satisfactory for the region 3650–10100Å which involves the 168th to 56th echelle orders. For a slit width of 640 μm amounting to 1.15 arcsec at the Coude focus, the actual spectral resolution (FWHM) is about 0.2Å at 8850Å. The length of the slit is chosen as 4.0 arcsec. Hyung (1994) & Aller (1994) describe the observing procedure. Since the Hamilton echelle was designed primarily for star-like sources, it is not useful for extended low surface brightness PN. The earlier observations were obtained with an 800 × 800 chip that did not cover the echelle field, so several settings were needed. Later, we used a slower 2048 × 2048 chip which covered the whole field and was somewhat more efficient at longer wavelengths. The program has been completed and definitive measurements have obtained for NGC 2440, NGC 6543, NGC 6741, NGC 6818, NGC 7026, NGC 7662, and Hu 1-2. All of these PN display particularly rich, interesting spectra. Previously observed and published objects include IC 351, IC 418, IC 2149, IC 4997, NGC 6567, NGC 6572, NGC 6790, NGC 6886, NGC 7009, BD +30 3639, & Hubble 12. NGC 6884 is in press. Additional nebulae which are yet to be discussed are IC 4634, IC 4846, IC 5117, NGC 6210, & NGC 6803.

scholarly journals The σc — Vcirc correlation in high and low surface brightness galaxies

2004 ◽  
Vol 220 ◽  
pp. 339-340 ◽  
Author(s):  
A. Pizzella ◽  
E. Dalla Bontà ◽  
E. M. Corsini ◽  
L. Coccato ◽  
F. Bertola
Keyword(s):  
Surface Brightness ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
High Surface ◽  
Linear Scale ◽  
High Surface Brightness ◽  
Circular Velocity ◽  
Straight Line ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

We investigate the relation between the central velocity dispersion, σc, and the circular velocity, Vcirc, in galaxies. in addition to previously obtained data, we consider an observationally homogeneus sample of 52 high surface brightness and 11 low surface brightness spiral galaxies. We performed a straight line regression analysis in a linear scale, finding a good fit, also for low σc galaxies, always rejected in the previous studies. Low surface brightness galaxies seem to behave differently, showing either higher values of Vcirc or lower values of σc with respect to their high surface brightness counterparts.

scholarly journals Morphology and Stellar Populations in the Gas-Rich, Giant LSBGs

1999 ◽  
Vol 171 ◽  
pp. 191-195 ◽  
Author(s):  
P. Knezek
Keyword(s):  
Entire Range ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
High Surface ◽  
Nuclear Spectroscopy ◽  
Nuclear Activity ◽  
High Surface Brightness ◽  
Low Surface Brightness ◽  
Show Evidence ◽  
Low Surface Brightness Galaxies

AbstractAn unexpected characteristic of low surface brightness galaxies (LSBGs) is that a significant number are massive and possess substantial amounts of atomic gas. We present preliminary results of an ongoing program to obtain BVRIJHK imaging, along with some nuclear spectroscopy, of a well-defined sample of LSBGs which are gas-rich and of similar size to giant, high surface brightness spiral galaxies (HSBGs). These LSBGs span the entire range of Hubble disk morphologies. While their disks are bluer, on average, than comparable HSBGs, the optical morphology of massive LSBGs indicates that many of these systems have undergone previous star formation episodes. They typically have long disk scale lengths, and range from MB = −16 to −22 (H0 = 75 km s−1 Mpc−1). About half of the LSBGs with bulges show evidence of nuclear activity, and ~30% appear to be barred. These massive, gas-rich LSBGs apparently have varied, and often complex, evolutionary histories.

scholarly journals Gasdynamics and Starbursts in Interacting Galaxies

1999 ◽  
Vol 186 ◽  
pp. 205-212 ◽  
Author(s):  
J. Christopher Mihos
Keyword(s):  
Surface Brightness ◽  
High Surface ◽  
Disk Surface ◽  
Interacting Galaxies ◽  
Host Galaxies ◽  
Direct Function ◽  
High Surface Brightness ◽  
Low Surface Brightness ◽  
The Stability ◽  
Low Surface Brightness Galaxies

The onset of gaseous inflows and central activity in interacting galaxies is driven largely by induced bars in the host galaxies. The stability of galaxies against growing bar modes is a direct function of their structural properties — galaxies with central bulges or low disk surface densities are more stable against central starbursts than are bulgeless or disk-dominated systems. Low surface brightness galaxies prove less prone to bar formation and central starbursts than do normal high surface brightness galaxies. This stability of LSB disks also resolves many of the dynamical pitfalls encountered when attempting to link poststarburst “E+A” galaxies to interactions involving normal high surface brightness galaxy progenitors.

scholarly journals UGC 1378 – a Milky Way sized galaxy embedded in a giant low surface brightness disc

2019 ◽  
Vol 489 (4) ◽  
pp. 4669-4678 ◽  
Author(s):  
Anna S Saburova ◽  
Igor V Chilingarian ◽  
Anastasia V Kasparova ◽  
Ivan Yu Katkov ◽  
Daniel G Fabricant ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Milky Way ◽  
High Surface ◽  
Wide Field ◽  
High Surface Brightness ◽  
Dispersion Data ◽  
Low Surface Brightness ◽  
Stellar Velocity ◽  
Major Merger ◽  
Gas Accretion

ABSTRACT The dominant physical processes responsible for the formation and longevity of giant gaseous and stellar discs in galaxies remain controversial. Although they are rare (less than 10 confirmed as of now), giant low-surface brightness (gLSB) discy galaxies provide interesting insights given their extreme nature. We describe observations of UGC 1378 including deep spectroscopy with the Russian 6-m telescope and multiband imaging with Binospec at the MMT. Galaxy UGC 1378 has both high surface brightness and an extended low surface brightness discs. Our stellar velocity dispersion data for the high surface brightness, Milky Way sized, disc appears inconsistent with a recent major merger, a widely discussed formation scenario for the very extended low surface brightness disc. We estimate the star formation rates (SFRs) from archival Wide-Field Infrared Survey Explorer data. The SFR surface density in the LSB disc is low relative to its gas density, consistent with recent gas accretion. We argue that the unusually large size of UGC 1378’s disc may be the product of a rich gas reservoir (e.g. a cosmic filament) and an isolated environment that has preserved the giant disc.

scholarly journals Low Surface Brightness Galaxies Around the Hubble Deep Field South

2007 ◽  
Vol 3 (S244) ◽  
pp. 354-355 ◽  
Author(s):  
L. Haberzettl ◽  
D. J. Bomans ◽  
R.-J. Dettmar
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Stellar Population ◽  
Stellar Populations ◽  
Low Surface Brightness ◽  
Galaxy Redshift ◽  
Low Surface Brightness Galaxies ◽  
Hubble Deep Field ◽  
Lsb Galaxies ◽  
Selection Of

AbstractWe present results from a study of the SFH of a sample of LSB galaxies around the HDF-S. For the selection of the LSB galaxy candidates we used color–color diagrams, from which we selected the candidates based on their different location in comparison to the HSB galaxy redshift tracks. We compared measured spectra to synthetic SEDs from synthesis evolution models. We were able to fit SEDs in the range of 2 to 5 Gyr to the spectra of the LSB galaxies, while applying the same method to a sample of HSB galaxies resulted in an averaged stellar population of about 10 to 14 Gyr. Therefore, LSB galaxies tend to show much younger averaged stellar populations. This implies that the major star formation event of LSB galaxies took place at a redshift of z ~ 0.2 to 0.4 while for HSB galaxies this tends to be at z ~ 2 to 4.

scholarly journals On the general structure of giant low surface brightness galaxy Malin 2

2012 ◽  
Vol 8 (S295) ◽  
pp. 236-236
Author(s):  
A. S. Saburova ◽  
A. V. Kasparova ◽  
I. Yu. Katkov ◽  
D. V. Bizyaev ◽  
I. V. Chilingarian
Keyword(s):  
Surface Brightness ◽  
General Structure ◽  
High Surface ◽  
Gas Pressure ◽  
Distribution Model ◽  
Dark Halo ◽  
Surface Photometry ◽  
Radial Profiles ◽  
Low Surface Brightness ◽  
The Galaxy

AbstractWe carried out the multicolor surface photometry in BVR and griz filters parallel with stellar kinematic measurements from the long slit spectra for the low surface brightness galaxy Malin 2. The use of the multicolor surface photometry as well as the available HI rotation curve allowed us to construct the mass distribution model of the galaxy. Photometrical and dynamical mass estimates agree with the dark halo mass fraction of about 70% within four disc radial scalelengths (~ 70 kpc). We used our dynamical model to obtain radial profiles of the equilibrium disc volume density and gas pressure in the galaxy midplane based on the available HI and CO data. The observed molecular gas fraction appears to be much higher than in the high surface brightness galaxies for a similar gas pressure.

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