scholarly journals Ultraviolet spectra of star-forming galaxies with time-dependent dust obscuration

2003 ◽  
Vol 212 ◽  
pp. 734-735
Author(s):  
Lucimara P. Martins ◽  
Claus Leitherer ◽  
Daniela Calzetti
Keyword(s):  
Stellar Wind ◽  
Time Dependent ◽  
New Technique ◽  
New Approach ◽  
Star Forming ◽  
Ultraviolet Spectra

We present a new approach to probe the properties of the most massive, ionizing stars with respect to the less massive, non-ionizing stars. The new technique utilizes stellar-wind lines, instead of the previously employed nebular lines. This allows us to probe the timescale of the dust dispersal in a very young obscured starburst from purely stellar diagnostics.

Ultraviolet Spectra of Star‐forming Galaxies with Time‐dependent Dust Obscuration

2002 ◽  
Vol 574 (1) ◽  
pp. 114-125 ◽  
Author(s):  
Claus Leitherer ◽  
Daniela Calzetti ◽  
Lucimara P. Martins
Keyword(s):  
Time Dependent ◽  
Star Forming ◽  
Ultraviolet Spectra

scholarly journals Measuring the H i Content of Individual Galaxies Out to the Epoch of Reionization with [C ii]

2021 ◽  
Vol 922 (2) ◽  
pp. 147
Author(s):  
Kasper E. Heintz ◽  
Darach Watson ◽  
Pascal A. Oesch ◽  
Desika Narayanan ◽  
Suzanne C. Madden
Keyword(s):  
Galaxy Evolution ◽  
Conversion Factor ◽  
Mass Density ◽  
Cosmic Time ◽  
Gas Content ◽  
Universal Relation ◽  
New Approach ◽  
Star Forming ◽  
Baryonic Mass ◽  
Individual Galaxies

Abstract The H i gas content is a key ingredient in galaxy evolution, the study of which has been limited to moderate cosmological distances for individual galaxies due to the weakness of the hyperfine H i 21 cm transition. Here we present a new approach that allows us to infer the H i gas mass M HI of individual galaxies up to z ≈ 6, based on a direct measurement of the [C ii]-to-H i conversion factor in star-forming galaxies at z ≳ 2 using γ-ray burst afterglows. By compiling recent [C ii]-158 μm emission line measurements we quantify the evolution of the H i content in galaxies through cosmic time. We find that M HI starts to exceed the stellar mass M ⋆ at z ≳ 1, and increases as a function of redshift. The H i fraction of the total baryonic mass increases from around 20% at z = 0 to about 60% at z ∼ 6. We further uncover a universal relation between the H i gas fraction M HI/M ⋆ and the gas-phase metallicity, which seems to hold from z ≈ 6 to z = 0. The majority of galaxies at z > 2 are observed to have H i depletion times, t dep,HI = M HI/SFR, less than ≈2 Gyr, substantially shorter than for z ∼ 0 galaxies. Finally, we use the [C ii]-to-H i conversion factor to determine the cosmic mass density of H i in galaxies, ρ HI, at three distinct epochs: z ≈ 0, z ≈ 2, and z ∼ 4–6. These measurements are consistent with previous estimates based on 21 cm H i observations in the local universe and with damped Lyα absorbers (DLAs) at z ≳ 2, suggesting an overall decrease by a factor of ≈5 in ρ HI(z) from the end of the reionization epoch to the present.

scholarly journals A New Technique to Solve the Instant Insanity Problem

2016 ◽  
Vol 11 (10) ◽  
pp. 5766-5773
Author(s):  
Salar Y Alsardary ◽  
Hwee Jung Kim ◽  
Julie George
Keyword(s):  
Graph Theory ◽  
Programming Language ◽  
New Technique ◽  
New Approach ◽  
A New Technique

Instant Insanity [1] consists of four cubes, each of whose six faces are colored with one of the four colors: red, blue, white, and green. The object is to stack the cubes in such a way that each of the four colors appears on each side of the resulting column. See figure 1 below[2]. Traditionally, this could be solved using graph theory.However, in this article, we introduce a new technique to solve the problem without using graph theory. We also used a Perl programming language to implement the new approach for the Instant Insanity.

An atlas of ultraviolet spectra of star-forming galaxies

1993 ◽  
Vol 86 ◽  
pp. 5 ◽  
Author(s):  
A. L. Kinney ◽  
R. C. Bohlin ◽  
D. Calzetti ◽  
N. Panagia ◽  
Rosemary F. G. Wyse
Keyword(s):  
Star Forming ◽  
Ultraviolet Spectra

Extracting Mode Shapes for Beams Through a Passing Auxiliary Mass

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Yao Zhang ◽  
Hai-Sheng Zhao ◽  
Seng-Tjhen Lie
Keyword(s):  
Experimental Validation ◽  
Simple Algorithm ◽  
Coupled System ◽  
Time Dependent ◽  
New Technique ◽  
Mode Shapes ◽  
Lumped Mass ◽  
Ridge Detection ◽  
Instantaneous Frequencies ◽  
Auxiliary Mass

This paper shows an approach to evaluate mode shapes for beams through using a passing auxiliary mass. The coupled system of an auxiliary mass passing over a beam is time-dependent, and the corresponding instantaneous frequencies (IFs) are equivalent to the mode shapes. Hence, reconstruction of the mode shapes is easy to be achieved through estimating the IFs. A simple algorithm based on ridge detection is proposed to reconstruct the mode shapes. This method is effective if the beam is light or the lumped mass is heavy. It is convenient since it requires an accelerometer mounted on the passing auxiliary mass rather than a serious of sensors mounted on the structure itself. It is also more practical because it is usually difficult to install external exciter. A lab-scale experimental validation shows that the new technique is capable of identifying the first three mode shapes accurately.

A Swept-Up Molecular Bubble in L1551

1989 ◽  
Vol 120 ◽  
pp. 260-263
Author(s):  
Saeko S. Hayashi ◽  
Masahiko Hayashi ◽  
Norio Kaifu
Keyword(s):  
Uv Radiation ◽  
Spectral Type ◽  
Stellar Wind ◽  
Shell Structures ◽  
The Sun ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Outflow ◽  
Dominant Activity

The environment of the young stellar object IRS5 in L1551 dark cloud is a representative of the “protostellar disk and outflow” systems found in star forming regions. The bipolar molecular outflow there was discovered as the first of its kind a decade ago (Snell, Loren, and Plambeck 1980). Its location in the sky, that is, its proximity (160 pc), isolation, and its almost edge-on inclination have favored the observation in great detail. IRS5 is thought to have the spectral type G - K (Mundt et al. 1985) similar to the Sun, with its dominant activity in the stellar wind, and not in the UV radiation as in massive protostars. The blueshifted and redshifted outflow lobes are clearly resolved into a pair of shell structures. The successive studies, mostly in CO lines, have led to a model of the outflow in which the molecular material is accelerated at the edge of a cavity evacuated by the protostellar wind (e.g. Uchida et al. 1987, Rainey et al. 1987, Moriarty-Schieven and Snell 1988).

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