- ID:
- ivo://CDS.VizieR/J/MNRAS/444/2456
- Title:
- Spectral galaxy pairs from SDSS DR9
- Short Name:
- J/MNRAS/444/2456
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral galaxy pairs (hereafter as SGPs) are composite galaxy spectra that contain two independent redshift systems. These spectra are useful for studying the dust properties of the foreground galaxies. In this article, a total of 165 spectra of SGPs are mined from the Sloan Digital Sky Survey (SDSS) Data Release 9 (DR9) using the concept of 'membership degree' from fuzzy set theory, especially defined to be suitable for fuzzy identification of emission lines. The spectra and images of this sample are classified according to their membership degree and image features, respectively. Many of the second redshift systems are too small or too dim to select from SDSS images alone, making the sample a potentially unique source of information on dust effects in low-luminosity or low surface brightness galaxies, which are underrepresented in morphological pair samples. The dust extinction of those objects with high membership degree is also estimated by Balmer decrement. Additionally, analyses for a series of spectroscopic observations of one SGP from 165 systems indicate that a newly star-forming region of our Milky Way might exist.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/423/133
- Title:
- Spectral indexes in HII galaxies
- Short Name:
- J/A+A/423/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the stellar content of a large number of HII galaxies from the continua and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these objects. We find that all galaxies of our sample contain an old stellar population (>=1Gyr) that dominates the stellar mass, and in a majority of these we also found evidence for an intermediate-age population >=50Myr apart from the presently bursting, ionizing young generation <=10^7^yr.
- ID:
- ivo://CDS.VizieR/J/AZh/71/200
- Title:
- Spectral Investigation of NGC 7469
- Short Name:
- J/AZh/71/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This investigation is mainly related to hydrogen lines in the spectrum of NGC 7469 from the 1972-1990 data obtained using an image tube on the 2.6-m telescope of the Crimean Astrophysical Observatory. The decomposition of the hydrogen lines into broad and narrow components was performed. Variations in the intensities and broad-component contours were observed. One third of the spectrograms showed a broad, symmetric Ha line, while the others showed asymmetry: the blue wings fall more steeply than the red ones. The degree of asymmetry is variable, but no correlation between it and the brightness of the nucleus was found. This asymmetry becomes weaker when passing to higher members of the Balmer series. The halfwidths of the broad components increase from Ha to H{gamma}. Redshifts of broad components with respect to narrow ones might also be larger for higher members of the Balmer series. Intensities of the broad hydrogen lines follow continuum variations with a delay of about 28 days. The Balmer decrement for broad lines is much flatter than for narrow ones.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1541
- Title:
- Spectral parameters for Mrk 335 and Ark 564
- Short Name:
- J/MNRAS/448/1541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive flux-resolved spectral analysis of the bright narrow-line Seyfert 1 AGNs, Mrk 335 and Ark 564 using observations by XMM-Newton satellite. The mean and the flux-resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low-energy soft excess and the other for the high-energy power law. A broad iron line and a couple of low-energy edges are required to explain the spectra. For Mrk 335, the 0.3-10 keV luminosity relative to the Eddington value, L_X_/L_Edd_, varied from 0.002 to 0.06. The index variation can be empirically described as {Gamma}=0.6log_10_L_X_/L_Edd_+3.0 for 0.005<L_X_/L_Edd_<0.04. At L_X_/L_Edd_~0.04 the spectral index changes and then continues to follow {Gamma}=0.6log_10_L_X_/L_Edd_+2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3-10 keV band by only a power law and an iron line. For Ark 564, the index variation can be empirically described as {Gamma}=0.2log_10_L_X_/L_Edd_+2.7 with a significantly large scatter as compared to Mrk 335. Our results indicate that for Mrk 335, there may be accretion disc geometry changes which lead to different parallel tracks. These changes could be related to structural changes in the corona or enhanced reflection at high flux levels. There does not seem to be any homogeneous or universal relationship for the X-ray index and luminosity for different AGNs or even for the same AGN.
- ID:
- ivo://CDS.VizieR/J/A+A/285/812
- Title:
- Spectral properties of X-ray extragal. sources
- Short Name:
- J/A+A/285/812
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+AS/131/295
- Title:
- Spectral survey of Case emission-line galaxies
- Short Name:
- J/A+AS/131/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of the follow-up spectroscopy of 178 emission-line galaxy (ELG) candidates from the Case objective-prism survey and nine Markarian galaxies with the 6m telescope are described. Only the candidates classified in the Case survey as those with emission lines were observed with the aim to form a statistical sample of blue compact galaxies (BCGs) with strong emission lines in the zone RA: 8h-16h, and DE: =+29deg-+38deg. We present the redshifts, equivalent widths and flux ratios for the strongest lines and the spectrum type for most of the galaxies with detected emission lines. A significant fraction (about 23%) of the observed Case galaxies do not show emission lines in blue. Preliminary analysis of the data is presented and the properties of the observed ELGs are compared with those of other known samples.
- ID:
- ivo://CDS.VizieR/J/A+A/396/503
- Title:
- Spectra of blue compact galaxies
- Short Name:
- J/A+A/396/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper in a series studying the star formation rates, stellar components, metallicities, and star formation histories and evolution of a sample of blue compact galaxies. We analyzed spectral properties of 97 blue compact galaxies, obtained with the Beijing Astronomical Observatory (China) 2.16m telescope, with spectral range 3580{AA}-7400{AA}. We classify the spectra according to their emission lines: 13 of the total 97 BCG sample are non-emission line galaxies (non-ELGs); 10 have AGN-like emission (AGNs), and 74 of them are star-forming galaxies (SFGs). Emission line fluxes and equivalent widths, continuum fluxes, the 4000A Balmer break index and equivalent widths of absorption lines are measured from the spectra. Please find more detail information in http://optik2.mtk.nao.ac.jp/~xkong/bcg/
- ID:
- ivo://CDS.VizieR/J/A+A/389/845
- Title:
- Spectra of blue compact galaxies
- Short Name:
- J/A+A/389/845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blue compact galaxies are compact objects that are dominated by intense star formation. Most of them have dramatically different properties compared to the Milky Way and many other nearby galaxies. Using the IRAS, HI data, and optical spectra, we wanted to measure the current star formation rates, stellar components, metallicities, and star formation histories and evolution of a large blue compact galaxy sample. We anticipate that our study will be useful as a benchmark for studies of emission line galaxies at high redshift. In the first paper of this series, we describe the selection, spectroscopic observation, data reduction and calibration, and spectrophotometric accuracy of a sample of 97 luminous blue compact galaxies. We present a spectrophotometric atlas of rest-frame spectra, as well as tables of the recession velocities and the signal-to-noise ratios. The recession velocities of these galaxies are measured with an accuracy of {delta}V<67km/s. The average signal-to-noise ratio of sample spectra is ~51. The spectral line strengths, equivalent widths and continuum fluxes are also measured for the same galaxies and will be analyzed in the next paper of this series.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A75
- Title:
- Spectra of 8 supergiants in nearby galaxies
- Short Name:
- J/A+A/562/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of episodic mass loss in massive star evolution is one of the outstanding questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the mid-infrared and dim at optical wavelengths. We aim to increase the number of investigated luminous mid-IR sources to shed light on the late stages of these objects. To achieve this we explore mid-IR selection criteria to identity dusty evolved massive stars in two nearby galaxies. The method is based on mid-IR colors, using 3.6um and 4.5um photometry from archival Spitzer Space Telescope images of nearby galaxies and J-band from 2MASS. We apply our criteria to two nearby star-forming dwarf-irregular galaxies: Sextans A and IC 1613, selecting 8 targets, which we follow up with spectroscopy. Our spectral classification and analysis yielded the discovery of 2 M-type supergiants in IC 1613, 3 K-type supergiants and 1 candidate F-type giant in Sextans A, and 2 foreground M giants. We show that the proposed criteria provide an independent way for identifying dusty evolved massive stars, which can be extended to all nearby galaxies with available Spitzer/IRAC images at 3.6um and 4.5um.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A178
- Title:
- Spectra of 2 z>3 hot dust-obscured galaxies
- Short Name:
- J/A+A/646/A178
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present the detection of H_2_O and OH+ emission in z>3 hot dust-obscured galaxies (Hot DOGs). Using ALMA Band-6 observations of two Hot DOGs, we have detected H_2_O(2_02_-1_11_) in W0149+2350, and H_2_O(3_12_-3_03_) and the multiplet OH+(1_1-0_1) in W0410-0913. These detections were serendipitous, falling within the side-bands of Band-6 observations aimed to study CO(9-8) in these Hot DOGs. We find that both sources have luminous H_2_O emission with line luminosities of L_H2O_>2.2x10^8^L_{sun}_ and L_H2O_=8.7x10^8^L_{sun}_ for W0149+2350 and W0410-0913, respectively. The H_2_O line profiles are similar to those seen for the neighbouring CO(9-8) line, with linewidths of FWHM~800-1000km/s. However, the H_2_O emission seems to be more compact than the CO(9-8). OH+ is detected in emission for W0410-0913, with a FWHM=1000km/s and a line luminosity of L_OH+_=6.92x10^8^L_{sun}_. The ratio of the observed H_2_O line luminosity over the IR luminosity, for both Hot DOGs, is consistent with previously observed star forming galaxies and AGN. The H_2_O/CO line ratio of both Hot DOGs and the OH+/H_2_O line ratio of W0410-0913 are comparable to those of luminous AGN in the literature. The bright H_2_O(2_02_-1_11_), and H_2_O(3_12_-3_03_) emission lines are likely due to the combined high star formation levels and luminous AGN in these sources. The presence of OH+ in emission, and the agreement of the observed line ratios of the Hot DOGs with luminous AGN in the literature, would suggest that the AGN emission is dominating the radiative output of these galaxies. However, followup multi-transition observations are needed to better constrain the properties of these systems.
