Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpatially Resolved Studies of Local Massive Red Spiral Galaxies
111
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report two-dimensional spectroscopic analysis of massive red spiral galaxies ($M_{*}$ $>$ 10$^{10.5}$ $M_{odot}$) and compare them to blue spiral and red elliptical galaxies above the same mass limit based on the public SDSS DR15 MaNGA observations. We find that the stellar population properties of red spiral galaxies are more similar to those of elliptical galaxies than to blue spiral galaxies. Red spiral galaxies show a shallow mass-weighted age profile, and they have higher stellar metallicity and Mgb/${rm langle Fe rangle}$ across the whole 1.5$R_{rm e}$ as compared to blue spirals, but all these properties are close to those of elliptical galaxies. One scenario to explain this is that red spirals form as remnants of very gas-rich major mergers that happened above $z$$sim$1.
rate research
Read More
We investigate the star formation histories (SFHs) of massive red spiral galaxies with stellar mass $M_ast>10^{10.5}M_odot$, and make comparisons with blue spirals and red ellipticals of similar masses. We make use of the integral field spectroscopy from the SDSS-IV/DR15 MaNGA sample, and estimate spatially resolved SFHs and stellar population properties of each galaxy by applying a Bayesian spectral fitting code to the MaNGA spectra. We find that both red spirals and red ellipticals have experienced only one major star formation episode at early times, and the result is independent of the adopted SFH model. On average, more than half of their stellar masses were formed $>$10 Gyrs ago, and more than 90% were formed $>6$ Gyrs ago. The two types of galaxies show similarly flat profiles in a variety of stellar population parameters: old stellar ages indicated by $D4000$ (the spectral break at around 4000AA), high stellar metallicities, large Mgb/Fe ratios indicating fast formation, and little stellar dust attenuation. In contrast, although blue spirals also formed their central regions $>$10 Gyrs ago, both their central regions and outer disks continuously form stars over a long timescale. Our results imply that, massive red spirals are likely to share some common processes of formation (and possibly quenching) with massive red ellipticals in the sense that both types were formed at $z > 2$ through a fast formation process.Possible mechanisms for the formation and quenching of massive red spirals are discussed.
Dust attenuation in star-forming spiral galaxies affects stars and gas in different ways due to local variations in dust geometry. We present spatially resolved measurements of dust attenuation for a sample of 232 such star-forming spiral galaxies, derived from spectra acquired by the SDSS-IV MaNGA survey. The dust attenuation affecting the stellar populations of these galaxies (obtained using full spectrum stellar population fitting methods) is compared with the dust attenuation in the gas (derived from the Balmer decrement). Both of these attenuation measures increase for local regions of galaxies with higher star formation rates; the dust attenuation affecting the stellar populations increases more so than the dust attenuation in the gas, causing the ratio of the dust attenuation affecting the stellar populations to the dust attenuation in the gas to decrease for local regions of galaxies with higher star formation rate densities. No systematic difference is discernible in any of these dust attenuation quantities between the spiral arm and inter-arm regions of the galaxies. While both the dust attenuation in the gas and the dust attenuation affecting the stellar populations decrease with galactocentric radius, the ratio of the two quantities does not vary with radius. This ratio does, however, decrease systematically as the stellar mass of the galaxy increases. Analysis of the radial profiles of the two dust attenuation measures suggests that there is a disproportionately high concentration of birth clouds (incorporating gas, young stars and clumpy dust) nearer to the centres of star-forming spiral galaxies.
Exploiting the sample of 30 local star-forming, undisturbed late-type galaxies in different environments drawn from the GAs Stripping Phenomena in galaxies with MUSE (GASP), we investigate the spatially resolved Star Formation Rate-Mass ({Sigma}SFR-{Sigma}_star) relation. Our analysis includes also the galaxy outskirts (up to >4 effective radii, re), a regime poorly explored by other Integral Field Spectrograph surveys. Our observational strategy allows us to detect H{alpha} out to more than 2.7re for 75% of the sample. Considering all galaxies together, the correlation between the {Sigma}SFR and {Sigma}_star is quite broad, with a scatter of 0.3 dex. It gets steeper and shifts to higher {Sigma}_star values when external spaxels are excluded and moving from less to more massive galaxies. The broadness of the overall relation suggests galaxy-by-galaxy variations. Indeed, each object is characterized by a distinct {Sigma}SFR-{Sigma}_star relation and in some cases the correlation is very loose. The scatter of the relation mainly arises from the existence of bright off-center star-forming knots whose {Sigma}SFR-{Sigma}_star relation is systematically broader than that of the diffuse component. The {Sigma}SFR-{Sigma}tot gas (total gas surface density) relation is as broad as the {Sigma}SFR-{Sigma}_star relation, indicating that the surface gas density is not a primary driver of the relation. Even though a large galaxy-by-galaxy variation exists, mean {Sigma}SFR and {Sigma}_star values vary of at most 0.7 dex across galaxies. We investigate the relationship between the local and global SFR-M_star relation, finding that the latter is driven by the existence of the size-mass relation.
We present a $^{13}mathrm{CO} (J = 1 rightarrow 0)$ mapping survey of 12 nearby galaxies from the CARMA STING sample. The line intensity ratio $mathcal{R} equiv I[^{12}mathrm{CO} (J = 1 rightarrow 0)]/I[^{13}mathrm{CO} (J = 1 rightarrow 0)]$ is derived to study the variations in molecular gas properties. For 11 galaxies where it can be measured with high significance, the spatially resolved $mathcal{R}$ on (sub-)kiloparsec scales varies by up to a factor of 3--5 within a galaxy. Lower $mathcal{R}$ values are usually found in regions with weaker $^{12}rm CO$. We attribute this apparent trend to a bias against measuring large $mathcal{R}$ values when $^{12}rm CO$ is weak. Limiting our analysis to the $^{12}rm CO$ bright regions that are less biased, we do not find $mathcal{R}$ on (sub)kpc scales correlate with galactocentric distance, velocity dispersion or the star formation rate. The lack of correlation between SFR and $mathcal{R}$ indicates that the CO optical depth is not sensitive to stellar energy input, or that any such sensitivity is easily masked by other factors. Extending the analysis to all regions with $rm ^{12}CO$ emission by spectral stacking, we find that 5 out of 11 galaxies show higher stacked $mathcal{R}$ for galactocentric radii of $gtrsim 1$ kpc and $Sigma_{mathrm{SFR}} lesssim 0.1 rm M_{sun} yr^{-1} kpc^{-2}$, which could result from a greater contribution from diffuse gas. Moreover, significant galaxy-to-galaxy variations are found in $mathcal{R}$, but the global $mathcal{R}$ does not strongly depend on dust temperature, inclination, or metallicity of the galaxy.
The global Schmidt law of star formation provides a power-law relation between the surface densities of star-formation rate (SFR) and gas, and successfully explains plausible scenarios of galaxy formation and evolution. However, star formation being a multi-scale process, requires spatially-resolved analysis for a better understanding of the physics of star formation. It has been shown that the removal of a diffuse background from SFR tracers, such as H$alpha$, far-ultraviolet (FUV), infrared, leads to an increase in the slope of the sub-galactic Schmidt relation. We reinvestigate the local Schmidt relations in nine nearby spiral galaxies taking into account the effect of inclusion and removal of diffuse background in SFR tracers as well as in the atomic gas.We used multiwavelength data obtained as part of the surveys such as SINGS, KINGFISH, THINGS, and HERACLES. Making use of a novel split of the overall light distribution as a function of spatial scale, we subtracted the diffuse background in the SFR tracers as well as the atomic gas. Using aperture photometry, we study the Schmidt relations on background subtracted and unsubtracted data at physical scales varying between 0.5--2 kpc. The fraction of diffuse background varies from galaxy to galaxy and accounts to $sim$34 % in H$alpha$, $sim$43 % in FUV, $sim$37 % in 24 $mu$m, and $sim$75% in H I on average. We find that the inclusion of diffuse background in SFR tracers leads to a linear molecular gas Schmidt relation and a bimodal total gas Schmidt relation. However, the removal of diffuse background in SFR tracers leads to a super-linear molecular gas Schmidt relation. A further removal of the diffuse background from atomic gas results in a slope $sim$1.4 $pm$ 0.1, which agrees with dynamical models of star formation accounting for flaring effects in the outer regions of galaxies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
