Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInternal Kinematics of Luminous Compact Blue Galaxies
161
0
0.0
(
0
)
Authors
Matthew A. Bershady
Ask ChatGPT about the research
No Arabic abstract
We describe the dynamical properties which may be inferred from HST/STIS spectroscopic observations of luminous compact blue galaxies (LCBGs) between 0.1<z<0.7. While the sample is homogeneous in blue rest-frame color, small size and line-width, and high surface-brightness, their detailed morphology is eclectic. Here we determine the amplitude of rotation versus random, or disturbed motions of the ionized gas. This information affirms the accuracy of dynamical mass and M/L estimates from Keck integrated line-widths, and hence also the predictions of the photometric fading of these unusual galaxies. The resolved kinematics indicates this small subset of LCBGs are dynamically hot, and unlikely to be embedded in disk systems.
rate research
Read More
The kinematic properties of the ionized gas of local Luminous Compact Blue Galaxy (LCBG) NGC 7673 are presented using three dimensional data taken with the PPAK integral field unit at the 3.5-m telescope in the Centro Astronomico Hispano Aleman. Our data reveal an asymmetric rotating velocity field with a peak to peak difference of 60 km s$^{-1}$. The kinematic centre is found to be at the position of a central velocity width maximum ($sigma=54pm1$ km s$^{-1}$), which is consistent with the position of the luminosity-weighted centroid of the entire galaxy. The position angle of the minor rotation axis is 168$^{circ}$ as measured from the orientation of the velocity field contours. At least two decoupled kinematic components are found. The first one is compact and coincides with the position of the second most active star formation region (clump B). The second one is extended and does not have a clear optical counterpart. No evidence of active galactic nuclei activity or supernovae galactic winds powering any of these two components has been found. Our data, however, show evidence in support of a previously proposed minor merger scenario in which a dwarf galaxy, tentatively identified with clump B, is falling into NGC 7673. and triggers the starburst. Finally, it is shown that the dynamical mass of this galaxy may be severely underestimated when using the derived rotation curve or the integrated velocity width, under the assumption of virialization.
In a programme of observations of local luminous blue compact galaxies (BCGs), we are investigating kinematics by using tracers of both stars and ionized gas. Here we summarise our program and present new data on the local Lyman break galaxy analogue Haro 11. From spatially-resolved spectroscopy around the near-infrared Ca II triplet, we find that its stars and ionized gas have similar velocity fields. Our programme so far indicates however that emission line velocities can differ locally by a few tens of km/s from the Ca II values. Comparing our data to simple stellar population models, we assess which stellar population the Ca II triplet traces and its potential beyond the local universe.
Luminous Compact Blue Galaxies (LCBGs) are common at z~1, contributing significantly to the total star formation rate density. By z~0, they are a factor of ten rarer. While we know that LCBGs evolve rapidly, we do not know what drives their evolution nor into what types of galaxies they evolve. We present the results of a single-dish HI survey of local LCBGs undertaken to address these questions. Our results indicate that LCBGs have M(HI) and M(DYN) consistent with low-mass spirals, but typically exhaust their gas reservoirs in less than 2 Gyr. Overall, the properties of LCBGs are consistent with them evolving into high-mass dwarf elliptical or dwarf irregular galaxies or low-mass, late-type spiral galaxies.
We use the KPNO International Spectroscopic Survey (KISS) for emission-line galaxies to identify and describe a sample of local analogues to the luminous compact blue galaxies (LCBGs) that are observed to be abundant at intermediate and high redshift. The sample is selected using criteria believed effective at isolating true examples of LCBGs: SB_e(B-band) < 21.0 mag/arcsec^2, M(B) < -18.5 (for H_o = 75 km/s/Mpc), and B-V < 0.6. Additionally, all LCBG candidates presented are selected to have star-formation as their dominant form of activity. We examine the properties of our LCBGs and compare them to those of other KISS star-forming galaxies of the same absolute magnitude range. We find that the KISS LCBGs lie on the extreme end of a fairly continuous distribution of ``normal star-forming galaxies in the plane of surface brightness versus color. This result differs from the results of previous studies that show LCBGs at higher-z to be more separate from the ``normal (usually non-active) galaxies they are compared against. On average, LCBGs have a higher tendency to emit detectable flux in the radio continuum, have higher H-alpha luminosities by a factor of 1.6, indicating strong star-formation activity, and have slightly lower than expected metal abundances based on the luminosity-metallicity relation for KISS galaxies. We calculate the volume density of our low-z (z<0.045) sample to be 5.4 x 10^-4 h_75^3 Mpc^-3, approximately 4 times lower than the volume density of the LCBGs at 0.4 < z < 0.7 and ~10 times lower than the volume density of the population at 0.7 < z < 1.0.
Luminous compact blue galaxies (LCBGs) are a diverse class of galaxies characterized by high luminosities, blue colors, and high surface brightnesses. Residing at the high luminosity, high mass end of the blue sequence, LCBGs sit at the critical juncture of galaxies that are evolving from the blue to the red sequence. Yet we do not understand what drives the evolution of LCBGs, nor how they will evolve. Based on single-dish HI observations, we know that they have a diverse range of properties. LCBGs are HI-rich with M(HI)=10^{9-10.5} M(sun), have moderate M(dyn)=10^{10-12} M(sun), and 80% have gas depletion timescales less than 3 Gyr. These properties are consistent with LCBGs evolving into low-mass spirals or high mass dwarf ellipticals or dwarf irregulars. However, LCBGs do not follow the Tully-Fisher relation, nor can most evolve onto it, implying that many LCBGs are not smoothly rotating, virialized systems. GMRT and VLA HI maps confirm this conclusion revealing signatures of recent interactions and dynamically hot components in some local LCBGs, consistent with the formation of a thick disk or spheroid. Such signatures and the high incidence of close companions around LCBGs suggest that star formation in local LCBGs is likely triggered by interactions. The dynamical masses and apparent spheroid formation in LCBGs combined with previous results from optical spectroscopy are consistent with virial heating being the primary mechanism for quenching star formation in these galaxies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
