The evolution of weak Mg II absorption lines

Toru Misawa, Ryan Lynch, Anand Narayanan, Nikola Milutinović, Tae Sun Kim, Jane Camilla Charlton

Research output: Contribution to journalArticle

Abstract

We present preliminary results of two surveys of weak Mg II (rest frame equivalent width Wr (2796) < 0.3Å) absorbers at 〈z〉=0.15 and at 〈z〉 = 1.75. For the low redshift survey, we used 25 HST/STIS echelle quasar spectra (R=45,000) that covered Si IIλ1260 and C IIλ1335 at 0 < z < 0.3. These transitions were used as a tracer of Mg IIλ2796, allowing a survey of redshift path-length g(z)=5.3. Our high redshift survey covers a redshift path-length of g(z)=6.7 in 15 high resolution QSO spectra obtained with UVES on VLT. We find that dN/dz=0.96±0.19 for 0 < z < 0.3 and 0.02 < Wr(2796) < 0.3Å, and dN/dz=1.05±0.16 for 1.4 < z < 2.2 over the same equivalent width range. These numbers are to be compared to the results of a previous survey of weak Mg II absorbers: dN/dz=1.74±0.10 for 0.4 < z < 1.4 (Churchill et al. 1999). There appears to be a peak epoch for weak Mg II absorbers at z∼0.9. At higher redshifts, the observed value is significantly less than expected for cosmological evolution, and somewhat smaller than expected considering the larger extragalactic background radiation at 〈z〉=1.75. We conclude from this that the processes that produce weak Mg II absorbing structures are equally, or somewhat less, active at 〈z〉 = 1.75 than at 〈z〉=0.9. At lower redshifts, 〈z〉=0.15, we would expect a larger number of weak Mg II absorbers than observed (comparing to intermediate redshifts). A significant fraction of these expected objects would result from the evolution of low density structures in which only C IV absorption was observable at higher redshifts. The overall evolution of weak Mg II absorbers is consistent with them being related to some type of global star formation activity, perhaps restricted to certain environments. More detailed examination of the evolution of the properties of weak Mg II absorbers is needed.

Original languageEnglish (US)
Pages (from-to)451-453
Number of pages3
JournalProceedings of the International Astronomical Union
Volume1
Issue numberC199
DOIs
StatePublished - Jan 1 2005

Fingerprint

absorbers
quasars
background radiation
tracer
tracers
star formation
examination
time measurement
high resolution

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics

Cite this

Misawa, Toru ; Lynch, Ryan ; Narayanan, Anand ; Milutinović, Nikola ; Kim, Tae Sun ; Charlton, Jane Camilla. / The evolution of weak Mg II absorption lines. In: Proceedings of the International Astronomical Union. 2005 ; Vol. 1, No. C199. pp. 451-453.
@article{c16543c9b7714c339888ca983157b0a5,
title = "The evolution of weak Mg II absorption lines",
abstract = "We present preliminary results of two surveys of weak Mg II (rest frame equivalent width Wr (2796) < 0.3{\AA}) absorbers at 〈z〉=0.15 and at 〈z〉 = 1.75. For the low redshift survey, we used 25 HST/STIS echelle quasar spectra (R=45,000) that covered Si IIλ1260 and C IIλ1335 at 0 < z < 0.3. These transitions were used as a tracer of Mg IIλ2796, allowing a survey of redshift path-length g(z)=5.3. Our high redshift survey covers a redshift path-length of g(z)=6.7 in 15 high resolution QSO spectra obtained with UVES on VLT. We find that dN/dz=0.96±0.19 for 0 < z < 0.3 and 0.02 < Wr(2796) < 0.3{\AA}, and dN/dz=1.05±0.16 for 1.4 < z < 2.2 over the same equivalent width range. These numbers are to be compared to the results of a previous survey of weak Mg II absorbers: dN/dz=1.74±0.10 for 0.4 < z < 1.4 (Churchill et al. 1999). There appears to be a peak epoch for weak Mg II absorbers at z∼0.9. At higher redshifts, the observed value is significantly less than expected for cosmological evolution, and somewhat smaller than expected considering the larger extragalactic background radiation at 〈z〉=1.75. We conclude from this that the processes that produce weak Mg II absorbing structures are equally, or somewhat less, active at 〈z〉 = 1.75 than at 〈z〉=0.9. At lower redshifts, 〈z〉=0.15, we would expect a larger number of weak Mg II absorbers than observed (comparing to intermediate redshifts). A significant fraction of these expected objects would result from the evolution of low density structures in which only C IV absorption was observable at higher redshifts. The overall evolution of weak Mg II absorbers is consistent with them being related to some type of global star formation activity, perhaps restricted to certain environments. More detailed examination of the evolution of the properties of weak Mg II absorbers is needed.",
author = "Toru Misawa and Ryan Lynch and Anand Narayanan and Nikola Milutinović and Kim, {Tae Sun} and Charlton, {Jane Camilla}",
year = "2005",
month = "1",
day = "1",
doi = "10.1017/S1743921305003054",
language = "English (US)",
volume = "1",
pages = "451--453",
journal = "Proceedings of the International Astronomical Union",
issn = "1743-9213",
publisher = "Cambridge University Press",
number = "C199",

}

Misawa, T, Lynch, R, Narayanan, A, Milutinović, N, Kim, TS & Charlton, JC 2005, 'The evolution of weak Mg II absorption lines', Proceedings of the International Astronomical Union, vol. 1, no. C199, pp. 451-453. https://doi.org/10.1017/S1743921305003054

The evolution of weak Mg II absorption lines. / Misawa, Toru; Lynch, Ryan; Narayanan, Anand; Milutinović, Nikola; Kim, Tae Sun; Charlton, Jane Camilla.

In: Proceedings of the International Astronomical Union, Vol. 1, No. C199, 01.01.2005, p. 451-453.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The evolution of weak Mg II absorption lines

AU - Misawa, Toru

AU - Lynch, Ryan

AU - Narayanan, Anand

AU - Milutinović, Nikola

AU - Kim, Tae Sun

AU - Charlton, Jane Camilla

PY - 2005/1/1

Y1 - 2005/1/1

N2 - We present preliminary results of two surveys of weak Mg II (rest frame equivalent width Wr (2796) < 0.3Å) absorbers at 〈z〉=0.15 and at 〈z〉 = 1.75. For the low redshift survey, we used 25 HST/STIS echelle quasar spectra (R=45,000) that covered Si IIλ1260 and C IIλ1335 at 0 < z < 0.3. These transitions were used as a tracer of Mg IIλ2796, allowing a survey of redshift path-length g(z)=5.3. Our high redshift survey covers a redshift path-length of g(z)=6.7 in 15 high resolution QSO spectra obtained with UVES on VLT. We find that dN/dz=0.96±0.19 for 0 < z < 0.3 and 0.02 < Wr(2796) < 0.3Å, and dN/dz=1.05±0.16 for 1.4 < z < 2.2 over the same equivalent width range. These numbers are to be compared to the results of a previous survey of weak Mg II absorbers: dN/dz=1.74±0.10 for 0.4 < z < 1.4 (Churchill et al. 1999). There appears to be a peak epoch for weak Mg II absorbers at z∼0.9. At higher redshifts, the observed value is significantly less than expected for cosmological evolution, and somewhat smaller than expected considering the larger extragalactic background radiation at 〈z〉=1.75. We conclude from this that the processes that produce weak Mg II absorbing structures are equally, or somewhat less, active at 〈z〉 = 1.75 than at 〈z〉=0.9. At lower redshifts, 〈z〉=0.15, we would expect a larger number of weak Mg II absorbers than observed (comparing to intermediate redshifts). A significant fraction of these expected objects would result from the evolution of low density structures in which only C IV absorption was observable at higher redshifts. The overall evolution of weak Mg II absorbers is consistent with them being related to some type of global star formation activity, perhaps restricted to certain environments. More detailed examination of the evolution of the properties of weak Mg II absorbers is needed.

AB - We present preliminary results of two surveys of weak Mg II (rest frame equivalent width Wr (2796) < 0.3Å) absorbers at 〈z〉=0.15 and at 〈z〉 = 1.75. For the low redshift survey, we used 25 HST/STIS echelle quasar spectra (R=45,000) that covered Si IIλ1260 and C IIλ1335 at 0 < z < 0.3. These transitions were used as a tracer of Mg IIλ2796, allowing a survey of redshift path-length g(z)=5.3. Our high redshift survey covers a redshift path-length of g(z)=6.7 in 15 high resolution QSO spectra obtained with UVES on VLT. We find that dN/dz=0.96±0.19 for 0 < z < 0.3 and 0.02 < Wr(2796) < 0.3Å, and dN/dz=1.05±0.16 for 1.4 < z < 2.2 over the same equivalent width range. These numbers are to be compared to the results of a previous survey of weak Mg II absorbers: dN/dz=1.74±0.10 for 0.4 < z < 1.4 (Churchill et al. 1999). There appears to be a peak epoch for weak Mg II absorbers at z∼0.9. At higher redshifts, the observed value is significantly less than expected for cosmological evolution, and somewhat smaller than expected considering the larger extragalactic background radiation at 〈z〉=1.75. We conclude from this that the processes that produce weak Mg II absorbing structures are equally, or somewhat less, active at 〈z〉 = 1.75 than at 〈z〉=0.9. At lower redshifts, 〈z〉=0.15, we would expect a larger number of weak Mg II absorbers than observed (comparing to intermediate redshifts). A significant fraction of these expected objects would result from the evolution of low density structures in which only C IV absorption was observable at higher redshifts. The overall evolution of weak Mg II absorbers is consistent with them being related to some type of global star formation activity, perhaps restricted to certain environments. More detailed examination of the evolution of the properties of weak Mg II absorbers is needed.

UR - http://www.scopus.com/inward/record.url?scp=63549131347&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=63549131347&partnerID=8YFLogxK

U2 - 10.1017/S1743921305003054

DO - 10.1017/S1743921305003054

M3 - Article

VL - 1

SP - 451

EP - 453

JO - Proceedings of the International Astronomical Union

JF - Proceedings of the International Astronomical Union

SN - 1743-9213

IS - C199

ER -